Abstract

In three previous papers many evidences were adduced proving the homology between stigmas and awns in sorghum. In the third paper the occurrence of basal feathered stigmas was recorded and also the fact that along with such occurrence and the presence of awns, the barbs of the subular portion of the awn were also basal in occurrence. The stigmas in sorghum are generally fully feathery (Fig. 1.). The length and disposition of the feathers may vary between varieties. The experience in the suppression of the feathers in the top portion of the usually feathery area of the stigma was met with in 26 sorghum varieties from Central and East Africa, i.e., N. Rhodesia, Nyasaland, Tanganyika and Kenya territories. These sorghums belong chiefly to the groups S. conspicuum Snowden and S. Roxburghii Stapf, groups characterised by gaping glumes. In these varieties the stigmatic portion is feathery at the base only with a bare cylindrical projection at the top (Fig. 2). The length of the feathery area varies from one-third to two-thirds the length of the stigma and is constant within the variety. To the naked eye, the non-feathery portion of the stigma appears smooth. Under the microscope, there are seen incipient projections, connoting suppressed feathers (Fig 4.). Stray feathery out- growths can occasionally be seen in this otherwise smooth looking area. This peculiar kind of stigma is constant in its occurrence in the varieties mentioned above and to our knowledge the first experience of its kind in the Gramineae. The setting of the seed is normal in spite of the restricted feathery area in the stigmas.

Keywords: