Morphological studies in the Gramineæ

Summary

The structure and vascular anatomy of the spikelet in the tribe Paniceæ has been studied. The present study reveals a striking similarity in the pattern of vascular supply to various parts of the spikelet in different species. An important feature is that the palea bundles arise conjointly with the laterals of its lemma and not from the vascular tissue destined to supply the floret proper (cf., Pooidæ where the palea bundles arise from the vascular tissue destined to supply the floret proper). This has been ascribed to extreme abbreviation of axes—the rachilla and the flower axis—so much so that their individuality has become altoghether obscure.

It has been concluded that the spikelet in the Paniceæ (and that of the Panicoideæ in general) has also arisen from a multi-flowered spikelet by suppression of the first floret to various extents and complete suppression of florets above the second floret followed by abortion of the rachilla.

The disposition of the various parts of the spikelet inPaspalum compactum reveals that the three glumes present are the I, II and IV and the III glume (lemma I) is conspicuously absent along with its subtended flower. This is contrary to the observations of earlier workers like Blatter and McCann (1935), Bor (1940), etc.

The occasional presence in the spikelet fascicle ofSetaria glauca of a second and third imperfect spikelet in addition to the normal perfect one, in place of bristle shoots (br ₂″b andbr ₁″b) strengthens and confirms Arber’s contention (1931) that each ultimate bristle shoot and not a single bristle is equivalent to a spikelet.