Cytologia 49: 583-595, 1984 Cytological Observations on Some West Himalayan Orchids Tribe: Epidendreae I (Subtribes: Pogoniinae, Thuniinae, Bletiinae, Coelogyninae, Epidendrinae) P. N. Mehra and S. K. Kashyap Department of Botany, Panjab University, Chandigarh, India Received October 20, 1982 Epidendreae is the largest tribe of the family Orchidaceae with 29 subtribes covering about 465 terrestrial and epiphytic genera. A great majority of them belong to the subtribes Sarcanthineae, Oncidiinae and Epidendrinae. All the genera with few exceptions possess hard and waxy pollinia which is genrally accepted to be an advanced character in the family Orchidaceae. The systematics of some of the genera is highly debatable. Bulbophyllum Thou. and Dendrobium Sw. with about 1400 species each belong to this category. Most of the epiphytic as well as terrestrial members of this tribe have great horticultural value for their fascinating flowers. Cytological information is still quite meagre considering its great numerical strength. Important contributions on the subject have been made by many workers (cf. Moore 1973, Tanaka and Kame moto 1972, 1974). Contributions on the Indian members of the tribe have been made by Sharma and Chatterji (1966), Vij and Mehra (1976), and Mehra and Sehgal (1974, 1975, 1976, 1978, 1980). Presently cytological investigations have been carried out on 56 West Himalayan species belonging to 26 genera included in 10 subtribes. These results are presented in a series of three papers. The present paper includes 14 species under 8 genera. Discussion, conclusions, and phyletic relationships of the tribe Epidendreae as a whole is presented in the last paper of the series. Material and methods All the taxa studied were collected in nature. Procedures adopted for meiotic studies from PMC's and EMC's as well as mitotic studies from root-tip squashes, are the same as described earlier (Mehra and Kashyap, 1983). The same applies with regard to the description of the karyotypes. All the photomicrographs were made at a uniform magnification of •~1510 except where otherwise stated. Table I summarises the results of the present investigation. A few notes are presented below for individual taxon. Results and discussion Subtribe: Pogoniinae Pfitz. Table 1. * Genus worked out for the first time . + New chromosome number added/B-chromosomes . 586 P. N. Mehra and S. K. Kashyap Cytologia49 Nervilia Comm. ex Gaud. The genus comprises a total 80 tropical and subtropical species and is confined to the old world. N. aragoana Gaud. is a terrestrial species which occurs between 1000-1500m in the Kumaon bills. It flowers earlier to the rainy season after which the leaves appear. Mitotic studies from root-tip revealed 2n=72 chromosomes. The chro mosomes in the complement have wide gradation in size. This count falls in line with the only previous record of 2n=72 by Chennave eraiah and Jorapur (1966). These authors reported variable numbers 2n=54, 72, 108 and 144 for different species of the genus and have suggested x=9 or 18 as its basic number. Undoubtedly polyploidy has played a considerable role in specia tion within the genus. Dressler and Dodson (1960) considered Pogoniinae close to Vanillinae and dis tantly placed from Sobraliinae, Arethusinae and Gastrodiinae. On the basis of occurrence of individual pollen grains in Vanilla and Pogonia, the two subtribes Vanillinae and Pogoniinae can further be considered as related to each other. They also seem primitive within the tribe Epidendreae where the general rule is the formation of hard and waxy pollinia. Subtribe: Thuniinae Schltr. This subtribe is not well represented in the Western Himalayas since Thunia is the only genus with a single species reported from the area. T. alba Reichb. occurs in the Kumaon hills as an epiphyte or lithophyte between the elevations of 1000-1500m. Its flowers are charming white and fragrant. The species has ornamental value. Flowering period is May-June. Twenty bivalents were clearly counted in the PMC's at M-I (Fig. 1). Secon dary associations of bivalents were noticed in about 20% cells (Fig. 2). However, the number of groups formed varied from cell to cell. Majority of the cells showed equal segregation of 20:20 chromosomes at A-I. They were secondarily associated at this stage too. Meiosis was mostly normal although occasionally a few laggards were seen at A-I. Pollen grains were associated in tetrads forming soft pollinia. Forty small chromosomes were counted at root tip mitosis . The chromosomes possesssed median or submedian primary constriction. The present count of n=20, 2n=40 for T. alba confirms the previous reports (cf. Mehra and Vij 1970, Vij and Mehra 1976). Mehra and Sehgal (1978) found an asynaptic strain with 2n=c. 40. Variable chromosome numbers 2n=42 and 2n= 44 are also on record (Tanaka 1964, Roy and Sharma 1972). Vij and Mehra (1976) suggested x=20 as the basic number for the genus on the basis of chromosome counts of n-20 in T. alba and T. marshalliana. The presence of variable number 2n=38, 40, 42 and 44 as reported in literature may suggest the role of aneuploidy in evolution within the genus. In the great tribe Epidendreae, the subtribe Thuniinae is considered to be primitive by Dressler and Dodson (1960) and distantly related to the subtribes Epidendrinae, Coelogyninae and Bletiinae . The occurrence of relatively large chro mosomes in members of the subtribe and individual pollen grains in one of its 1984 Cytological Observations on Some West Himalayan Orchids 587 Figs. 1-8. Thunia alba: 1 and 2, PMC showing 20 bivalents at M-I. Note secondary associations in Fig. 2. 3-4: Calanthe puberula. 3, somatic cell with 2n=40+1B (at arrow). 4, a polysomatic cell (2n=80+2B's at arrow) •~1160. C. mannii: 5, a somatic cell with 40 chromosomes. C. trivarinata: 6, haploid complement (n=20) at pollen mitotic metaphase. Pachystoma senile: 7, 8, PMC and EMC with 20 bivalents at diakinesis respectively. Note smaller size of bivalents in EMC. 588 P. N. Mehra and S. K. Kashyap Cytologia49 members, Arundina (cf. Mehra and Sehgal, unpublished), also suggest its primiti veness. Subtribe Bletiinae Bentham Calanthe R. Br. It is a genus of perennial ornamental plants comprising nearly 120 species met in warm climates (Airy Shaw 1973) with a wide range of distribution from South Africa and the Islands of the Indian Ocean through India to China and Japan and further south and eastwards from Malaysia to Australia and Tahiti (Santapau and Kapadia 1966). Duthie (1960) recorded 7 species from the Western Himalayas. Many species of this genus are exploited horticulturally. C. puberula Lindl. grows in moist situations on rotting leaf-mold in thick forests at an elevation of about 2200 m. Mitotic studies from root-tips revealed the chro mosome number to be 2n=40+1B (Fig. 3, B-chromosome at arrow). The chromo somes showed consistent size gradation measuring from 3.44-1.45ƒÊ. Total chro mosome length is 93.24ƒÊ. Karyotype formula is 14m+18 sm+8 st. The B-chro mosome was observed in all the dividing cells. A few polyploid cells were observed with double the chromosome number and 2B's (Fig. 4, B's at arrows). Gametic chromosome number n=20 was reported by Arora (1968) and Mehra and Vij (1970) for this species but the occurrence of a B-chromosome is reported for the first time. C. manii Hook. f. is met in humus rich soil under thick shady forests at an altitude of about 2100m in the Kumaon hills. Somatic studies from root tips reve aled 2n=40 chromosomes at metaphase (Fig. 5). The chromosomes showed mild gradation in size and appear to possess median or submedian primary constriction, The present count of 2n=40 falls in line with the earlier reports of n=20 by Mehra and Sehgal (1974) and Vij et al. (1976). C. tricarinata Lindl, grows in shady places in forests at an altitude of about 2500m in the Western Himalayas. Its flowering period is June-July. Twenty chro mosomes were clearly counted at pollen mitotic metaphase (Fig. 6). The chromo somes measured from 3.70-2.11 p. Total chromosome length of the haploid com plement is 59.33ƒÊ. Karyotype is symmetrical with 15m+5sm chromosomes (Fig. 17). Pollen grains form soft pollinia. The present count of n=20 is in accord with the earlier records (cf. Tanaka and Kamemoto 1972, 1974). Ito and Mutsuura (1958) reported 2n=40, 60 for this species. Darlington and Wylie (1955) suggested x=20 as the basic number for the genus. Majority of species of the genus possess n=20 or 2n=40. Triploid taxon with 2n=60 was found only in C. tricarinata (Ito and Mutsuura 1958). Other numbers reported in the genus are 2n=38, 42, 44 and 58 (cf. Tanaka and Kamemto 1972, 1974, Tanaka et al. 1981). Pachystoma senile Reichb. f. A terrestrial species distributed in the plains and foothills of Northern India from Garhwal to Sikkim, Khasi hills and Manipur , Presently it was collected from the plains on sandy soil among Saccharum bushes. Its flowering period is March April. 1984 CytologicalObservations on SomeWest HimalayanOrchids 589 Meiotic studies revealed 20 bivalents at diakinesis (Fig. 7). The bivalents were ring or rod-shaped. Secondary associations among some of them were seen in a few PMC's at M-I. Laggards were common at A-I and sometimes a fragment was also noticed. Bridges and laggards were seen even at T-II. Pollen grains form soft Figs. 9-16: Coelogyne cristata . 9, somatic cell with 2n=40 at metaphase. C. stricta: 10, somatic cell with 2n=40 at metaphase . C. ovalis: 11, somatic cell with 2n=40 at metaphase.