1968 411 

Structure and Behaviour of Chromosomes in 

Bauhinia and Allied Genera 
Arun Kumar Sharma and D 
. Tulsi Raju 
Cytogenetics Laboratory 
, Department of Botany, University of Calcutta , 35 
, Ballygunj Circular Road, Calcutta 19 
, India 
Received November 11, 1967 
Introduction 
The genera Bauhinia, Phanera and Piliostigma studied here 
, are included within the tribe 
Bauhinieae in the family Caesalpinaceae under De Wit's revised system of classification (1956). In the earlier 
system of Bentham and Hooker, all these three genera were included under Bauhinia within the monotype tribe 
Bauhinieae under the suborder Caesalpinieae of the order Leguminosae. The simple bilobed leaf-an outstanding 
character of this genus is principally responsible for its separate tribal status. This character is not only conspicuous 
but is universally present in all the species with slight variations in the extent of lobation. Taxonomically it is 
regarded as a uniform genus by all taxonomists, regarding it as a natural assemblage. The habit of the plants too is 
quite uniform, being mostly large or small trees. 
From the point of view of cytology, the genus is remarkable as well in that most of the species are 
characterised by a uniform chromosome number of 2n=28 (Atchison 1951, Miege 1960, Raghavan 1957, Turner 
1956b, Turner and Irwin 1961 and Turner and Fearing 1959). Only in Bauhinia monandra, Poucques (1945) reported 
42 chromosomes in the somatic cells, thus maintaining the same basic set of 14 chromosomes. 
The importance of cytological study in solving the problems of taxonomic dispute as well as in tracing 
interrelationships, affinities and evolution of different taxa is well established. Not only the chromosome number but 
the detailed chromosome morphology as well are taken into serious consideration in such studies. In a number of 
cases such as in the genus Lilium (Stewart and Bamford 1943), etc., slight variations in chromosome morphology 
are associated with evolution even though the chromosome number in all the taxa is constant. Lately, the invention 
of a number of pre-treatment chemicals has considerably aided the study of chromosome morphology in detail 
(Sharma 1956a). With the aid of these methods, minute differences in the study of karyotype too can easily be 
detected. These three genera evidently provide an ideal material for such an investigation. 
Cursory  examinations  of  the  somatic  chromosomes  of  these  genera  in  dicated  that  the  materials  are  not  very 
favourable for such investigation especially due to the heavy cytoplasmic content and very small chromosomes. 
 
412 A. K. Sharma and D. T. Raju Cytologia 33 
Evidently,  this  is  the  principal  reason  why  it  has  been  lying  unexplored.  After  a  series  of  trials  in different chemicals a method 
has been standardized, with which the present investigation was carried out. 
Materials and methods 
The present cytological investigation was carried out on twenty-four 
species and varieties of the genera Bauhinia, Phanera and Piliostigma. 
All of them have been collected from the Indian Botanical Gardens at 
Sibpur, Howrah and from Jamshedpur in Bihar. 
Temporary orcein squash method has been found to be very suitable 
for the study of somatic chromosomes. Of different pre-treatment chemicals 
tried, isopsoralene was found to be the most effective one in producing well 
scattered metaphase plates with clarified constrictions (Chaudhuri, Chakraborty 
and Sharma 1962). Healthy young root-tips were pretreated in saturated solu 
tion of isopsoralene for 21/2 to 4 hours in cold (9•Ž-10•Ž), fixed in propionic 
acid: ethyl alcohol (1:2) solution for about 45 minutes to an hour and stained 
by gently heating for a few seconds in a mixture of 2% aceto-orcein and 
N-HCl solutions (9:1). They were kept as such for overnight and the tip 
portions were subsequently squashed in 1% aceto-orcein solution or 45% 
acetic acid on a slide by applying uniform pressure over the coverslip and 
blotting off the excess stain. The slides thus prepared were properly sealed 
and observed under the microscope. 
The aceto-orcein squashes were made permanent by first removing the 
wax seal and then by inverting them in a petri-dish containing normal butyl 
alcohol till the coverslip was detached from the slide and were subsequently 
mounted in euparal. 
For meiotic studies, both smear and permanent sections were prepared 
from flower buds. Anthers of suitable size were smeared and stained in 1% 
propiono-carmine solution, after a long period (3-4 days) of fixation in pro 
piono: alcohol (1:3). Preparations in propiono-carmine gave much better 
results than those with any other chemical. 
Block preparations were also carried out as usual after the fixation of 
flower buds in Nawashin's fluids A and B (1:1) for overnight, following 
pre-treatment in Carnoy's fluid and washing in water. Sections were cut 14ƒÊ 
thick and stained following Newton's Crystal Violet Schedule. Mordanting 
in a mixture of 10% acetic acid and 1% chromic acid (1:9) for overnight 
before staining was found to be essential. 
Observations were made and figures drawn at a table magnification of 
approximately •~1400 using a Leitz compensating eye-piece of •~12.5 in com 
bination with an apochromatic objective 1.3 and an aplanatic condenser of 
1.4N. A. In the figures, chromosomes with secondary constrictions were drawn 
in outlines only. 
 
1968 Structure and Behaviour of Chromosomes in Bauhi 
nia 413 

Observations The somatic chromosome numbers of the different species 

and varieties of Bauhinia, Phanera and Piliostigma so far investigated have been found to range from 
2n=16 to 2n=28. A number of nuclei have been found to possess varying numbers of chromosomes, other 
than the normal number 
, in the same tissue containing the 
normal number, in several species 
. The normal number in such cases had to be 
determined from frequency counts and the number which has been found to be present in the highest 
frequency in the nuclei has been regarded as the normal one. A detailed karyotype analysis of the 
different species and varieties reveals a gross similarity in complements . The species can be 
distinguished from each other by minute differences in the details of chromosome structure, including the 
secondary constrictions. The chromosomes, on an average, are very short in length, in comparison to the 
cells, which are very large. Size difference is present, though not very marked. There is a gradual 
gradation from the comparatively longer to short ones. Though the chromosomes are in general short, still 
on the basis of their relative length they can be divided into two groups, viz., comparatively long and 
short. Long chromosomes are generally provided with a satellite at the end of one of the arms. Karyotypes 
of all the species and varieties investigated in the present paper reveal that on the basis of gross morpho 
logical features a number of chromosome types is common to all of them. A critical analysis, however, 
shows that minor alterations in the representatives of the types are met with in different species which 
may be considered as criteria for the identification of these species. A significant coincidence in the total 
amount of chromatin matter of all the species and varieties is ob served. The general types will be 
described separately in the beginning and their finer differences will be dealt with under karyotype 
description for each species. The main types which have been noted are as follows: 
Type A-Long chromosome with nearly median to median primary con striction and a satellite at the 
distal end of the slightly short arm. 
Type B-Short chromosome with nearly median to median primary con striction. 
The  different  species  differ  in  having  different  numbers  of  the  above  types.  A  detailed  karyotype 
analysis of different species and varieties is dealt with separately in the following text. 
Meiotic studies show very large P. M. C.'s with heavy cytoplasmic con tent and very small 
chromosomes. During meiosis, diakinesis and metaphase I reveal 14 bivalents except in Bauhinia 
diphylla, B. hookeri, B. rufeseence, B. retusa, Phanera integrifolia and Piliostigma malabaricum. The 
irregu larities noted in some of the species are lagging, early separation, inversion bridge, restitution 
nucleus, nondisjunction, secondary association, polyspory and accumulation of chromatin matter in the 
form of nuclei ranging in size and number from a few to many. 
 
414 A. K. Sharma and D. T. Raju Cytologia 33 
Figs. 1. 1, 1a, 3, 3a, 5, 5a, 6, 6a, 18, 18a, 23, 23a, 37, 37a, 42, 42a, 44, 44a, 47, 47a, 50, 50a, and 52, 52a. Normal somatic 
metaphase plates and idiograms of Bauhinia acuminata, B. blakeana, B. corniculata, B. diphylla, B. galpini, B. hookeai, B. 
monandra (Type 1), P. monandra (=B. krugii, Type II), B. petersiana, B. purpurea, B. purpurea var. purpurea and B. racemosa 
respectively. 24-26, 45 and 48. Variation somatic metaphase 
plates of B. hookeri, B. petersiana and B. purpurea. 
 
1968 Structure and Behaviour of Chromosomes in Bauhinia 415 
1. Bauhinia aouminata Linn. 2n=28=A6+B22=1 
.8ƒÊ to 2.9ƒÊ (Figs. 1 
to 1a). 
Meiotic studies show large P. M. C.'s with regular fourteen bivalents 
(Fig. 2). 
2. B. blakeana Dunn. 2n=28=A6+B22=1.8ƒÊ to 3.2ƒÊ (Figs 
. 3 and 3a). 
Meiotic studies show large P. M. C.'s with regular normal fourteen bivalents 
(Fig. 4). Meiotic irregularities show cells with extra chromosomal droplets 
of stainable bodies along with the bivalents ranging both in size and number 
from one to numerous. 
3. B. corniculata Benth. 2n=28=A6+B22=1.4ƒÊ to 3.1ƒÊ (Figs. 5 and 
5a). 
4. B. diphylla Buch. 2n=28=A4+B24=1.45 to 2.5ƒÊ (Figs. 6 and 6a). 
Meiotic studies show very large P. M. C.'s with regular normal fourteen 
bivalents (Fig. 7), along with other variation plates with thirteen and twelve 
bivalents respectively (Figs. 8 and 9). Secondary association of bivalents in 
metaphase I is observed, the maximum association or the lowest number of 
grouping being 1(5)+1(4)+4(1). The irregularities noted at metaphase II 
are 12-12 and 13-13 chromosomes at each pole in each mother cell respec 
tively (Figs. 10 and 11). The other irregularities noted are restitution nucleus, 
inversion bridge with a fragment, non-disjunction and polyspory respectively 
(Figs. 12, 13, 14 and 15, 16, 17). Each polyspore contains very small to big 
spores in varying numbers from 6 to 13 onwards. 5. B. galpini N. E. Br. 
2n=28=A6+B22=1.8ƒÊ to 3.2ƒÊ (Fig. 18 and 18a). 
Meiotic studies show very large P. M. C.'s, with fourteen bivalents at diakinesis 
and metaphase I stages (Figs. 19 and 20). Diakinesis stage shows extra chro 
mosomal droplets of stainable bodies with one or two bivalents attached to 
one of it. The irregularities noted are polyspory, containing spores varying 
in size and number from 6 onwards in each cell (Figs. 21 and 22). 
6. B. hookeri F. Muell. 2n=28=A8+B20=1.4ƒÊ to 3.2ƒÊ (Figs. 23 and 
23a). 
In addition to the normal karyotype represented above, variations both 
in number and structure of the chromosomes have also been observed. Nu 
merical variations showing lower numbers of 2n=26, 18 and 16 chromosomes 
respectively (Figs. 24, 25 and 26) have been recorded. 
Meiotic studies show very large P. M. C.'s with regular normal fourteen 
bivalents both at diakinesis and metaphase I (Fig. 27). Numerical variations 
showing lower numbers of n=13, 12, 10, 9, 8, 7 and 6 bivalents respectively 
(Figs. 28, 29, 30, 31, 32, 33 and 34) have also been recorded. The irregularities 
noted are non-disjunction of 11-9 and 12-13 chromosomes at each pole of a 
pollen mother cells (Figs. 35 and 36) respectively. 
7. B. monandra Kurz. Type I. 2n=28=A6+B22=1.4ƒÊ to 3.2ƒÊ (Figs. 
37 and 37a). 
Meiotic studies show very large P. M. C.'s with regular normal fourteen 
 
416 A. K. Sharma and D. T. Raju Cytologia 33 
bivalents both at diakinesis and anaphase I (Fig. 38). Metaphase II shows 14-14 chromosomes on both the poles of 
the mother cell (Fig. 39). The 
Figs. 2, 4, 7-17 and 19-22. Meiotic stages of B. acuminata, B. blakeana, B. diphylla and 
B. galpini respectively. 

irregularity noted is polyspory, the cells containing spores of various size and number. The number of 
spores varies from 7-11 (Figs. 40 and 41). 
 
1968 Structure and Behaviour of Chromosomes in Bauhinia 417 
8. B. monandra Kurz. Type II (=B. krugii Urban). 2n=28=A4+B24 
=1.4ƒÊ to 2.2ƒÊ (Figs. 42 and 42a). 
Meiotic 
studies show 
large 
P. M. C.'s 
with regular 
normal four 
teen biva 
lents at meta 
phase I (Fig. 
43). 
9. B. 
petersiana 
C. Bolle. 2n 
=28=A6+ 
B22=14ƒÊ to 
2.9ƒÊ (Figs. 
44 and 44a). 
In ad 
dition to the 
normal 
karyotype 
represented 
above, a 
variation 
nucleus with 
2n=26 chro 
mosomes has 
also been 
recorded 
(Fig. 45). 
Meiotic 
studies show 
large 
P. M. C.'s 
with regular 
fourteen 
bivalents at 
metaphase I 
(Fig. 46). 
10. B. 
Figs. 27-36, 38, 43, 83, 85-86 and 87-90. Meiotic stages of Bauhinia hookeri, B. monandra (Type I), B. monandra (=B. krugii, 
Type II), Phanera semibifida (=B. semibifida), Piliostigma malabaricum (=B. malabarica plant No. 1) and P. malabaricum (Plant 
No. 2) respectively. 
purpurea Linn. 2n=28=A6+B22=1.4ƒÊ to 2.5ƒÊ (Figs. 47 and 47a). 
Cytologia 33, 1968 28 
 
418 A. K. Sharma and D. T. Raju Cytologia 33 
Figs. 53-54 and 61-64. Variation somatic metaphase plates of B. racemosa and B. rufescence respectively. 56, 56a, 60, 60a, 68, 
68a, 70, 70a, 72, 72a, 74, 74a, 76, 76a, 78, 78a, 79, 79a, 82, 82a and 84, 84a. Normal somatic metaphase plates and idiograms of 
B. retusa (=Lasiobema 
 
1968 Structure and Behaviour of Chromosomes in Ba 
uhinia 419 
In addition to the normal karyotype represented above 
, a variation nucleus with 2n=26 chromosomes has 
also been recorded (Fig 
. 48). 
Meiotic studies show large P 
. M. C.'s with regular fourteen bivalents at 
metaphase I (Fig. 49). 
11. B. purpurea Linn. var 
. purpurea. 2n=28=A6+B22=1 
.4ƒÊ to 2.9ƒÊ 
(Figs. 50 and 50a). 
Meiotic studies show large P 
. M. C.'s with regular fourteen bivalents at 
metaphase I (Fig. 51). 
12. B. racemosa Lam. 2n=28=A8+B20=1 
.8ƒÊ to 2.9ƒÊ (Figs. 52 and 52a). 
In addition to the normal karyotype represented above 
, variation nuclei containing 2n=24 and 22 
chromosomes respectively have also been noted 
(Figs. 53 and 54). 
Meiotic studies show large P. M 
. C.'s with regular fourteen bivalents at 
metaphase I (Fig. 55). 
13. B. retusa Roxb. (=Lasiobema retusum (Roxb 
.) de Wit, comb. nov.) 
2n=28=A6+B22=1.4ƒÊ to 3.6ƒÊ (Figs 
. 56 and 56a). 
Meiotic studies show large P. M 
. C.'s with regular fourteen bivalents both 
at diakinesis and metaphase I (Fig. 57). Numerical variations showing lower 
numbers of 13 and 12 bivalents respectively have also been recorded (Figs 
. 
58 and 59). 
14. B. rufescence, Lam. 2n=28=A8+B20=1.4ƒÊ to 2 
.9ƒÊ (Figs. 60 and 
60a). 
In addition to the normal karyotype represented above, variations both 
in number and structure of chromosomes have also been observed. Numerical 
variations showing higher and lower numbers of 2n=56 
, 26, 22 and 18 chro 
mosomes respectively were seen (Figs. 61, 62, 63 and 64). 
Meiotic studies show large P. M. C.'s with regular fourteen bivalents both 
at diakinesis and metaphase I (Fig. 65). Numerical variations showing lower 
numbers of 11 and 9 bivalents respectively have also been recorded (Figs. 66 
and 67). 
15. B. tomentosa Linn. 2n=28=A6+B22=1.4ƒÊ to 2.9ƒÊ (Figs. 68 and 
68a). 
Meiotic studies show large P. M. C.'s with regular fourteen bivalents (Fig. 
69). Meiotic irregularities show the cells with extra chromosomal droplets 
of stainable bodies along with bivalents present in it. These stainable bodies 
range from one to numerous in number and also range in size from small to 
big. 
16. B. variabilis Hort. 2n=28=A4+B24=1.4ƒÊ to 2.1ƒÊ (Figs. 70 and 
70a). 
Meiotic studies show large P. M. C.'s with regular fourteen bivalents at 
retusum), B. rufescence, B. tomentosa, B. variabilis, B. variegate, B. variegate var. alboflava, B. variegata var. variegata, Phanera 
corymbosa (=B. corymbosa), Ph. integrifolia (=B. vahlii), Ph. semibifida (=B. semibifida) and Piliostigma malabaricum (=B. 
malabarica) respectively. 
 
420 A. K. Sharma and D. T. Raju Cytologia 33 
metaphase I (Fig. 71). 
17. B. variegata Linn. 2n=28=A4+B24=1.4ƒÊ to 2.9ƒÊ (Figs. 72 to 72a). 
Figs. 39-41, 46, 49, 51, 55, 57-59, 65-67, 69, 71, 73, 75, 77 and 80-81. Meiotic stages of B. monandra (Type I), B. petersiana, B. 
purpurea, B. purpurea var. purpurea, B. racemosa, B. retusa (=Lasiobema retusum), B. rufescence, B. tomentosa, B. variabilis, B. 
variegata, B. variegata var. alboflava, B. variegata var. variegata and Phanera integrifolia (=B. vahlii) respectively. 91, histogram 
of different species 
and varieties of Bauhinia, Phanera and Piliostigma. 
Meiotic 
studies show 
large 
P. M. C's 
with regular 
normal 
fourteen 
bivalents at 
metaphase I 
(Fig. 73). 
18. B. 
variegata L. 
var. albo 
flava de Wit, 
var. nov. 2n 
=28=A4+ 
B24=1.8ƒÊ to 
3.2ƒÊ (Figs. 
74 and 74a). 
Meiotic 
studies show 
large 
P. M. C.'s 
with regular 
fourteen bi 
valents (Fig. 
75). 
19. B. 
variegata, 
Linn. var. 
v ariegata. 
2n=28=A4 
+B24=1.4ƒÊ 
to 3.2ƒÊ (Figs. 
76 to 76a). 
Meiotic 
studies show 
large 
P. M. C.'s 
with regular 
normal four 
 
1968 Structure and Behaviour of Chromosomes in Bauhinia 421 
teen bivalents at metaphase I (Fig. 77) 
. 
20. Phanera corymbosa (Roxb.) Benth 
. (=Bauhinia corymbosa Roxb.) 
2n=28=A8+B20=1.4ƒÊ to 2.9ƒÊ (Figs. 78 and 78a) 
. 
21. Ph. integrifolia (Roxb.) Benth 
. (=B. vahlii Wight and Am 
.) 2n= 
28=A6+B22=1.4ƒÊ to 2.9ƒÊ (Figs. 79 and 79) 
. 
Meiotic studies show large P. M. C.'s with regular fourteen bivalents at 
metaphase I (Fig. 80). Numerical variation shows a lower number of 13 
bivalents (Fig. 81). 
22. Ph. semibifida (Roxb.) Benth 
. (=B. semibifida, Roxb. Hort.) 
2n=28=A4+B24=1.4ƒÊ to 2.5ƒÊ (Figs. 82 and 82a) 
. 
Meiotic studies show large P. M. C.'s with regular fourteen bivalents at 
metaphase I (Fig. 83). 
23. Piliostignaa malabaricum (Roxb.) Benth. (=Bauhinia malabarica 
Roxb., Hort.). (Plant No. 1). 2n=28=A6+B22=1.8ƒÊ to 3.2ƒÊ (Figs 
. 84 and 
84a). 
Meiotic studies show very large P. M. C.'s with regular normal fourteen bivalents both at diakinesis and 
metaphase I (Fig. 85). Two bivalents are attached to the nucleolus at the diakinesis stage (Fig. 86). 
24.  P.  malabaricum (Roxb.) Benth. (=B. malabarica Roxb., Hort.). (Plant No. II). Meiotic studies show large P. 
M. C.'s with clear small twenty one bivalents both at diakinesis and metaphase I respectively (Figs. 87 and 88) 
. The irregularity noted 
is early separation (Figs. 89 and 90). 
This plant was collected from a different location of the same compound, which is exactly similar in all 
respects with the plant number 1 of the same species from another locality. 
Discussion 
Chromosome studies of different species of Bauhinia, Phanera and Piliostigma so far carried out by different 
authors have all shown a 2n number of twenty-eight chromosomes, excepting Bauhinia monandra with 2n=42 
(Atchison 1951, Pantulu 1942 and Poucques 1945). During the present in vestigation not only the same number has 
been recorded in some of the species but at the same time, in no case, species have been recorded with a 
chromosome number which is not a multiple of 7. This is a fair indication of the fact that these three genera 
represent quite a homogeneous and natural assemblage in which multiplication of chromosomes plays an important 
role in evolution to some extent. 
In majority of the species, however, the chromosome number is constant with 2n=28 and chromosome 
morphology grossly identical in all. Therefore, the inclusion of Bauhinia, Phanera and Piliostigma under a single 
genus Bauhinia by Bentham and Hooker appears to be justified on the basis of cytological data. 
In one species, Piliostigma malabaricum, both diploid and polyploid 
 
422 A. K. Sharma and D. T. Raju Cytologia 33 
numbers have been observed. The habitat of the two species is however identical. An interesting feature about the polyploid is the 
formation of 21 bivalents with no multivalents. Apparently the absence of multivalents pre cludes the possibility of the species 
being an autopolyploid. But in view of the very size of the small chromosomes, which will have low chiasma fre 
quency at the diploid level, the formation of multivalents may be checked. Possibly also, some other structural changes might 
have been an associated feature in evolution along with polyploidy. In that case the absence of multi valents can no doubt be 
explained. The other possibility is to assume an allopolyploid origin which is rather unusual in view of the very little difference in 
phenotypic characters of diploid and polyploid individuals. It is reasonable to assume that the polyploid observed in P. 
malabaricuin is auto rather than an allopolyploid. In no other species however both auto and allopolyploid features have been 
observed. 
The occurrence of 21 bivalents in P. malabaricurm raises an important issue as to whether 14 or 7 chromosomes should be 
the basic set of the 
genus. In all probability it indicates 7 to represent the basic set of chromo somes. In that case all the species of these genera with 
twenty-eight chro mosomes should be regarded as representing stable allopolyploid types, in which hybridization must have 
occurred at an early phase in evolution. A diploid species with 7 bivalents, probably may be available in areas where the species 
grows wild. 
That the number 14 may be derived one, is indicated by the occasional occurrence of secondary association of 
bivalents in certain species, namely, Bauhinia diphylia. However, in other species no clear secondary association of 
bivalents has been observed. These facts clearly indicate that though the number n=14 for Bauhinia, Phanera and 
Piliostigma is a secondarily derived one, yet it has become deep-seated for these genera. 
Karyotype alterations and evolution of species. 
The species of Bauhinia, Phanera and Piliostigma studied so far reveal very interesting data. With the aid of the 
special techniques improvised for somatic chromosomes of these genera, the details of karyotypes of all the species 
have been worked out. All species studied in general show a gross resemblance in the nature of the karyotype in 
rather short chromosomes with gradation in size but with no abrupt size difference in the complements. The nature 
of the primary constriction is nearly identical being mostly median in position. All these facts taken in conjunction 
with the uniformity in the chromosome number in different taxa of these genera suggest that it repre sents a natural 
assemblage. 
In  spite  of  these  gross  similarities,  however,  differences  have  been  noticed  between  species  in minute details, 
involving  the  number and position of the secondary constrictions. In addition, various groupings of the two principal 
types of the chromosomes in varying numbers are also observed. These 
 
1968 Structure and Behaviour of Chromosomes in Bauhinia 423 
facts,  which  could  only  be  clarified  through  the  common pretreatment chemicals applied for all the species, suggest 
the  importance  of  minute  structural  alter  ations  of  chromosomes  in  the  evolution  of  the  different  species  of  these 
genera 
. The total amount of 
chromatin matter 
, as represented in the histogram (Fig. 91), reveals the close 
relationship in the chromatin content of all the species. On the one hand such similarity indicates the homogeneity of 
the taxon and on the other it suggests that structural alterations have principally involved rearrangement of parts and 
not deletion or duplication of segments. This has kept the general chromosome size too at a particular level. Further, 
karyotype alterations which otherwise maintain uniformity in chromosome size possibly have been favoured in the 
selection of species of these genera. 
A hypothetical problem arises in view of the regular occurrence of bi valents in different species of these 
genera. Why, in spite of the structural alterations, is meiosis almost regular at least in majority of the species? The 
answer is quite simple. These genera being of horticultural importance have been continually subjected to judicious 
selection. Evidently prolonged evolu tion followed by careful selection has been responsible for the maintenance of 
those species only which are homozygous for such structural changes. However, other evidences of structural 
changes exemplified by meiotic ir regularities are not uncommon in this genus. Though regular bivalent formation is 
the rule, non-disjunction, early separation, lagging, etc., suggest the presence of structurally altered chromosomes in 
the complement. 
Definite  evidence  of  such  heterozygosity  has  been  observed  at least in one species where a dicentric inversion 
bridge  with  an  acentric  fragment  has  been  recorded.  The  fate  of  gametes  arising  out  of  such  heterozygosity  is  not 
fully  known.  It  is  likely  that  such  inversion  heterozygosity  as  noted  in  Bauhinia  is  principally  maintained  through 
extensive propagation by cuttings in horticulture. 
Polysporous condition arising out of further mitotic division following meiosis has been observed in B. 
diphylla, B. galpini and B. monandra. In such polysporous types, though in all the cases the chromosome number 
could not be counted, the number does not seem to be identical in all the spores. Either such abnormal numbers arise 
through abnormalities in meiosis or in mitotic division of the tetrad nuclei. The fate of gametes arising out of this 
behaviour is difficult to predict. Most likely they degenerate and do not give rise to viable gametes. This is an 
assumption based on the fact that pro pagation of the species is not mainly through sexual means. Because of 
extensive vegetative propagation, meiotic abnormalities having no evolutionary possibilities are maintained in the 
plants. 
In  addition  to  the  presence  of  14  bivalents  in  the  meiotic  cells,  P.  M.  C.'s  have  been  recorded  showing  the 
occurrence  of  a large number of stainable bodies in the nuclei of some of the species, such as B. blakeana, B. galpini 
and B. tomentosa. It is very difficult to state at present their exact chemical 
 
424 A. K. Sharma and D. T. Raju Cytologia 33 
constitution. Being carmine-positive there is the possibility of their being of nucleic acid constitution. Critical 
cytochemical tests are needed to work out their exact nature in terms of chemical make-up. The presence of such 
bodies has been reported earlier by different workers in various plant materials (Dutt 1949, Painter 1943 and Sharma 
1955). Such conditions are generally met with in plants which have been subjected to environmental changes either 
partially or wholly. This may be the reason why they show such abnormal be haviour. In every organism a settled 
ratio between the two types of nucleic acid, i.e., DNA and RNA is being maintained. A breakdown of this balance is 
always harmful to the metabolism of the organism concerned. As under such conditions of abnormal environment, 
any of these two acids may be synthesized more as compared to the others. Such excess of synthesis may ultimately 
bring about certain disruption of normal metabolism. Plants in order to get rid of this excess of nucleic acid form 
extra chromosomal droplets of stainable bodies in the cell. Evidently, if it contains DNA it becomes Feulgen 
positive and if RNA it becomes pyronin positive. That is the reason why in certain species of plants such bodies are 
Feulgen positive whereas in others they are not so. 
Numerical variations have been observed in the somatic tissue of a number of species, such as B. hookerii, B. 
petersiana, B. purpurea, B. racemosa and B. rufescence. Such numerical variations occur along with cells having 
normal chromosome numbers, the latter no doubt occurring in a very high frequency. In many species the variations 
have been found to persist even upto meiotic cells. The importance of such alterations in the somatic tissue is 
immense, specially in plants where propagation is through vegetative means (Sharma 1956b). Bauhinia, Phanera and 
Piliostigma no doubt are extensively cultivated through cuttings. But in view of the fact that none of the species so 
far studied shows 2n number other than a multiple of 14, such aneuploid alterations in the somatic tissue probably 
play very little role in the origin of new races or species of these genera. Similarly, meiotic abnormalities observed 
in several species seem to have little significance as may possibly result in the formation of non-viable gametes. 
This assumption is borne out by the fact that none of the species contains an aneuploid chromosome number in the 
normal somatic cells. 
Variations in number occurring in the somatic complement no doubt have been detected, but at the same time 
it is possible that structural alterations of chromosomes, if any, in cells with otherwise normal somatic numbers, 
might have escaped detection. This is quite likely in view of the small size of the chromosomes. Structural 
abnormalities occurring in low frequency may therefore have every chance of evading detection. Then the 
importance of structural alterations of chromosomes in the evolution of new genotype in these genera is expected 
through vegetative propagation. This fact needs serious consideration as species of these genera are extensively 
propagated by 
 
1968 Structure and Behaviour of Chromosomes in Bauhinia 425 
cutting, and at the same time differ with respect to the structure of chromo somes. 
Summary 
The paper deals with cytological investigations on twenty 
-four  species  and  varieties  of 
Bauhinia, Phanera and Piliostigma . Both meiotic and detailed karyotype studies were done using isopsoralene 
, as a pre-treatment agent. In majority of the species the 
chromosome number is 2n=28 excepting P 
. malabaricum. In this 
species both n=14 and 21 chromosomes have been observed. On this basis the allopolyploid nature of the polyploid 
forms has been suggested. 
Whether 14 or 7 chromosomes should be the basic set of these genera is debatable. All chromosome numbers 
as yet recorded are multiples of 7. The occasional occurrence of secondary association of bivalents in certain 
species, namely Bauhinia diphylla, shows that the number 14 may be a derived 
one. 
All the species of Bauhinia, Phanera and Piliostigma show a gross similarity in the nature of karyotype, having 
rather short chromosomes with gradation in size. Due to the marked resemblance in karyotype, these three genera 
apparently represent a homogeneous assemblage and their inclusion within the same genus Bauhinia under Bentham 
and Hooker's system appears to be justified. Minute karyotype differences exist between different species and 
varieties suggesting the role of structural alteration of chromosomes in the evolution of species. Variations in 
chromosome number and chromosome morphology have been recorded in many species. These variations suggest 
that speciation and evolution in these species have been made possible through them being brought into effect 
through vegetative propagation. Drastic struc tural alterations have not been observed possibly due to the small size 
of the chromosomes. 
The histogram reveals a similarity in the chromatin content in all the species, indicating the homogeneity of the 
taxa and suggesting that structural alterations have principally involved rearrangement of parts and not deletion or 
duplication of segments. These genera, being horticultural ones, have been continually subjected to judicious 
selection and homozygosity has also been attained for structural alterations. 
P.  M.  C.'s  also  show  a  large  number  of  extra-chromosomal  droplets  of  stainable  bodies  in  the  cell.  Being 
carmine-positive  they  may  have  a  nucleic  acid  constitution.  The  reason  for  their  formation  through  disturbance  of 
DNA: RNA ratio has been discussed. 
Definite evidences of heterozygosity namely, inversion bridge, have been observed in Bauhinia diphylla. Such 
inversion heterozygosity as noted in Bauhinia is principally maintained through extensive propagation by cuttings in 
horticulture. The possible reasons for the occurrence of polyspory and its fate have been discussed. 
 
426 A. K. Sharma and D. T. Raju Cytologia 33 
References 
Atchison, E. 1951. Studies in Leguminosae. VI. Chromosome numbers among tropical 
woody species. Amer. J. Bot. 38: 538. Chaudhuri, M., Chakraborty, D. P. and Sharma, A. K. 1962. Isopsoralene and its 
use in 
karyotype analysis. Stain Techn. 37: 95-97. Dutt, M. 1949. Cytogenetics of some ornamental Jasmines. Abstract, Proc. 
36th Ind. Sci. 
Congr. Miege, J. 1960. Nombres chromosomiques de plantes d'Afrique Occidentale. Rev. cyt. 
Biol. veg. 21: 373-384. Painter, T. S. 1943. Cell growth and nucleic acids in the pollen of Rhoeo discolor. Bot. 
Gaz. 105: 58-68. Pantulu, J. V. 1942. Chromosome numbers of some Caesalpiniaceae. Curr. Sci. 11: 152 
-193. Poucques, M. L. De 1945. Rev. Cytol., Paris, 8: 117. Taken from 'The chromosome atlas of flowering plants. By C. 
D. Darlington and A. P. Wylie 1955. George Allen & Unwin Ltd., London. Raghavan, R. S. 1957. Chromosome numbers in 
Indian medicinal plants. Proc. Ind. Acad. 
Sci. B. 45: 294-298. Sharma, A. K. 1955. Cytology of some of the members of Commelinaceae and its bearing 
on the interpretation of phylogeny. Genetica 27: 323-363. - 1956a. Fixation of plant chromosomes. Bot. Rev. 22: 665-695. 
- 1956b. A new concept of a means of speciation in plants. Caryologia 9: 93-130. Stewart, R. N. and Bamford, R. 1943. The 
nature of polyploidy in Lilium tigrinum. 
Amer. J. Bot. 30: 1-7. Turner, B. L. 1956b. Chromosome numbers in the Leguminosae. I. Am. Jour. Bot. 43: 
577-581. - and Irwin, H. S. 1961. Chromosome numbers of some Brazilian Leguminosae. Rhodora 
63: 16-19. - and Fearing, O. S. 1959. Chromosome numbers in the Leguminosae. II. African species, 
including phyletic interpretations. Am. Jour. Bot. 46: 49-57. Wit, H. C. D. De. 1956. A revision of Malaysian Bauhinieae. 
Reinwardtia 3: 381-539.