160 Cytologia 22 Cytotaxonomy of the Andropogoneae II. Subtribes Ischaeminae, Rottboelliinae, and the Maydeae Robert P. Celarier Department of Botany and Plant Pathology, Oklahoma A. & M. College, Stillwater, Oklahoma, U. S. A. Received March 5, 1957 Introductory remarks, key to the subtribes, materials and methods, and the review of the subtribes Dinzeriinae and Saccharinae have been treated previously (Celarier, 1956b). Consequently, this report shall commence im mediately with the subtribes to be considered in this study. Subtribe III. Ischaenzinae Hack. Although the stout fused condition of the joints and pedicels marks this subtribe as rather more advanced than the Saccharinae, it almost always has two flowers, awned fertile spikelets and must be considered as rather primitive on morphological grounds. Pilger (1940) divides the subtribe into two groups, the Ischaenzininae and the Apludininae. In general this follows the plan of Stapf (1919), Bews (1929) and Keng (1939) and there is fair agreement among these workers concerning the materials considered in each division, although there are some differences regarding the status of various entries. The major exception is Keng's treatment in which Sehirna and Apluda are placed in the Euandro pogoneae and Arthraxon is included in the Ischaenzinae. Although Sehima and Apluda have been retained in the Ischaenzinae in this study, it has seemed advisable to follow Keng's example in regard to Arthraxon. It ap pears definitely to be related to Thelepogon in regard to the tuberculate or muricate lower glumes of the sessile spikelets and the cordate lanceolate leaves. Key to the genera of the Ischaeminae AA. Racemes several to many noded, not enclosed in a sheath (Ischaemi ninae). A. Racemes 3-many, digitate or nearly so. I. Rachis joints and pedicels more or less thickened, first glume of the sessile spikelet without tubercules or muricate, leaves not cordate..................................Ischaemum subgen. Coelischaemum II. Rachis joints and pedicels slender, first glume of sessile spikelet tuberculata or muricate, leaves lanceolate cordate. 1. Sessile spikelets two flowered, lemma awned from between the sinus...........................Thelepogon 1957 Cytotaxonomy of the Andropogoneae II 161 2. Sessile spikelets one flowered , lemma awned from the back or at base ......................... ..Arthraxon B. Racemes binate, rachis joints and pedicels triangular .................................... ......Ischaenzum Subgen. Euischaemum C. Racemes usually solitary. I. Pedicellate spikelets more or less reduced, glumes without wings. 1. Pedicillate spikelet neuter but almost as large as sessile. a. Joints and pedicels much thickened .. Ischaenzum Subgen. Digastriunz b. Joints and pedicels almost linear .....Sehima 2. Pedicellate spikelets reduced to the lower glume , much smaller than the sessile........ ..............Kerriochloa II. Pedicellate spikelets male . 1. Upper glume of both spikelets with wing-like crest .................................... Andropterum 2. Glumes not winged. .................Pogonachne BB. Racemes with one node, three heteromorphic reduced spikelets contain ed in a sheath (Apludininae).......... ........Apluda Of the eight genera included in this subtribe only two, Ischaernunz and Arthraxon, have more than a few known species. With the exception of fschaenzum, which has 3-4 species in America, all are restricted to the Eastern Hemisphere with the greatest number of genera and species in South east Asia. Only four genera are known cytologically. Ischaemum L. This is an extremely large and complex genus with well over fifty species and distributed throughout the tropics of the world. Two subgenera, Euischaemum and Coelischaemum, are recognized by both Keng (1939) and Pilger (1940) and it appears entirely possible from Hubbard's report (1935) that a third group Digastriunz may be distinct. Several sections have been recognized and described in the subgenus Euischaemum (Pilger 1940). Subgenus Coelischaemum I. brachyatherum Fenzl. was available for this study from a single collection made in Southern Rhodesia. It was found to have twenty somatic chromosomes with ten bivalents at metaphase I (Fig. 1) and completely re gular meiotic behavior. I. glaucostachyum Stapf was studied by Gould (1956) from two South African collection. Both had 2n=20 but no report of the meiotic behavior was given. Subgenus Euischaemum I. rugosum Salisb. from a collection in Assam, India, was found to be 2n=18 with nine bivalents at diakinesis (Fig. 2) and metaphase I. It was completely regular throughout its meiotic divisions. A second accession of Cytologia 22, 1957 11 162 R. P. Celarier Cytologia 22 this species came from a collection near Sao Paulo, Brazil. This was also found to have 18 somatic chromosomes with nine bivalents at metaphase I (Fig. 3) and regular meiotic behavior. I. tinzorense Kunth. was first studied by Bremer (1925) and was reported to have twenty somatic chromosomes. However, in this study, from materials collected at Taichung, Formosa, it was seen to be 2n=36. At diakinesis and metaphase I the normal condition was 18 bivalents (Fig. 4) but occasion ally two univalents were present. At anaphase and telophase I chromosome behavior was completely regular with 18: 18 distribution. I. ciliare Retz was studied from material collected at Turrialba, Costa Rica. This material yielded extremely poor preparations at diakinesis and metaphase I and it was only after considerable effort that fifteen cells were analyzed. In all of these the 2n number appeared to be 54, but only six cells had 27 bivalents. More frequently 2-4 univalents were seen (Fig. 5) and in one cell a quadrivalent was observed. I. diplopogon Hook. from the Aravalli Mts. of India was found to have a somatic number of forty. The meiotic divisions were completely regular throughout and there were consistently twenty bivalents at diakinesis (Fig. 6) and metaphase I (Fig. 7). I. arcuaturn Stapf from South Africa was reported by de Wet (1954) to have a somatic complement of twenty chromosomes. A more recent study (de Wet and Anderson 1956) has recorded 2n=50 indicating a polyploid series. No meiotic studies were made for either accession. I. guianense Kunth. was studied by Krishnaswamy (1941) and was found to be 2n=40. I. crassipes Thell. var. typicum was found by Moriya and Kondo (1950) to have 56 somatic chromosomes with 28 bivalents at metaphase I. However, an accession of this species, collected for this study by A. Moriya from Yakasidi, Japan, appears to be 2n=60. Although the chromosomes stained distinctly, their behavior was essentially regular, and their size was not ex ceedingly small, it was nevertheless difficult to determine the number with certainty. This seems to be principally due to the clumping of the chromo somes, especially at metaphase I, and, to a lesser extent, was the result of quadrivalent formation (Figs. 8, 9, 10). Because of this difficulty 75 cells were analyzed at diakinesis and meta phase I. Of these cells, four were found that had 28 bivalents and one quadrivalent, and 15 others were probably of this constitution (Fig. 8). Fifteen cells had 28 configurations (Fig. 9) and it appears likely that most of these were cases of two groups of two cells lying together. The remain ing 41 cells all seemed definitely to have 30 bivalents. Anaphase and telophase I were essentially regular, but occasionally two chromosome pairs appeared to be late in separating, and in one cell a bridge, without a fragment, was seen. It seems probable that these irregularities 1957 Cytotaxonomy of the Andropogoneae II 163 Figs. 1-12. Chromosome behavior in the Ischaeminae. 1350•~. 1, metaphase I in Ischaemum brachyatherum with ten bivalents. 2, diakinesis of I. rugosum from Assam with nine bivalents (chromosomes traced in India ink and the photograph bleached with K3 Fe (CN)6). 3, metaphase I of I. rugosum from Brazil showing nine bivalents. 4, diakinesis of I. timorense showing 18 bivalents. 5, metaphase I in I. ciliare with two univalents. 6, diaki nesis in I. diplopogon with 20 bivalents (two are very small). 7, metaphase I of I. diplo pogon with 20 bivalents (two lying together at arrow). 8, diakinesis of I. crassipes with 28 bivalents and one quadrivalent (arrow at quadrivalent). 9, prometaphase I of I. cras sipes with 28 configurations. 10, diakinesis in I. crassipes with thirty bivalents. 11, anaphase I in Sehima nervosum from India showing several lagging chromosomes. 12, metaphases I of Arthraxon hispidus with 18 bivalents, 164 R. P. Celarier Cytologia 22 were due to the slower separation of the occasional quadrivalent. A detailed study of several accessions of this species may prove fruitful but with the present information it appears that this species is 2n=60 and has a basic number of ten (or five) rather than seven as suggested by Moriya and Kondo (1950). I. anthephoroides Miq. was studied by Kuwada (1915) and reported to have a somatic number of 68. A more recent study of this species (Tateoka, 1955) has recorded 72 somatic chromosomes and the author suggested aneu ploidy in the species. No meiotic studies have been reported and the species definitely needs a more detailed analysis. Although only ten species of the genus have been studied cytologically, it is already obvious that at least two basic numbers, nine and ten, are known and it is at least possible that another, seven, exists. It is very likely that this large genus may indicate more than one line of evolution and a detailed analysis of the morphological and cytological variation in the group should prove extremely fruitful. Sehima Forsk. This is a small genus with only eight or nine described species. It appears to be closely related to Ischaemum and was considered only a section of Ischaemum by Hackel (Hackel 1889). It is widespread in the Old World tropics occurring from West Africa to Australia, and one species, S. nervo sum Stapf, covers most of this area. S. nervosum was first reported by Sampath and Ramanathan (1949) as having 34 somatic chromosomes. However, in a later study Mehra (1955) demonstrated that the species has a polyploid series with a basic number of ten.