Cytotaxonomic notes on the generaIndigofera L. andCyamopsis DC.

Abstract

Continuing cytotaxonomic research in the generaCyamopsis andIndigofera, this time with attention payed for the greater part to East Tropical African species yielded the following results:

• 1. Except for four rather small subsections ofIndigofera proper and the related genusRhynchotropis Harms, information was obtained about all Taxa. Of the 283 species described inGillett'ss monograph, some 80 species, among them a few with subspecies and varieties, now have been cytologically examined.

• 2. All through both generaCyamopsis andIndigofera there exists a diversity in dimensions and types of chromosomes which usually does not appear to be consistent with the accepted taxonomical classification.

• 3. Nevertheless,Cyamopsis thus far is characterized by2n=14 chromosomes, whereas2n=16 chromosomes is the most common number inIndigofera. On the other hand the sectionIndigastrum of the latter genus uniformly has2n=14 chromosomes, strengthening the supposition that this section may be closely related toCyamopsis.

• 4. The speciesI. macrocalyx Guill. & Perr. classified in thePaniculatae has2n=12 chromosomes. The speciesI. emarginella Steud. exA. Rich. classified in theTinctoriae has2n=24, favouring the suggestion that the 48-chromosome Himalayan and East-Asiatic shrubbyIndigofera's may not be hexaploids with base numberx=8, but octoploids in anx=6 range.

• 5. Polyploidy in thex=8 range, such as2n=32 seems to be fairly common all through the genusIndigofera and occurs, perhaps, more in the widely-spread African-Asiatic-(American) sections and subsections than in the African endemic taxa. In some cases the habitat of these polyploids appeared to be in higher altitudes and/or under less favourable climatic conditions.

• 6. The occurrence of giant chromosomes in the number2n=8 inI. richardsiae Gillett points to a new base number ofx=4 in theLeguminosae and suggests that theGaleaeae may be considered as a very old group. The2n=16 plants, consequently, must be taken as tetraploids.

• 7. Implications as to evolutionary relationship in theIndigofera and adjacent genera for the present appear to be impossible on the basis of cytotaxonomy. At most may be suggested that an intricate polyphylesis lies at the roots of theGalegeae and its genera.