Studies on seeds with ruminate endosperm

Summary

The six genera of the Vitaceæ studied show varying extent of perichalazal growth after fertilization. Ingrowths of rumination are produced by the integumentary tissues as a result of localised growth from the raphe region at the ventral side of the seed and their location in the mature seed is determined by the extent of perichalazal growth. InLeea the perichalaza itself becomes pushed in as an ingrowth and in addition to this four more ingrowths are produced; inCissus, Vitis, Tetrastigma andAmpelocissus the number of ingrowths is only two and these are situated away from the perichalaza; inCayratia the ingrowth is a single dome-shaped structure with two small longitudinal ridges at the inner face.

The nucellus increases after fertilization, and becomes ruminate by the ingrowths of the seedcoat. The endosperm remains quiescent and of small volume until the seed attains almost its mature size, but thereafter grows rapidly and replaces all the nucellus, thereby acquiring the same ruminate configuration. The mature endosperm contains fatty reserves and one druses in each cell.

The mechanical tissue of the mature seedcoat is completely derived from the innermost layer of the outer integument and is of varying layers thick in the different genera. The middle layers of the outer integument become tanniferous to varying extent in the different genera. The innermost layer of the inner integument becomes tanniferous, the outermost becomes spirally thickened and these two persist in the mature seed, whereas the middle layer acts as a nutritive layer and becomes completely crushed. Raphides occur in the seedcoat of all the genera exceptLeea.