Comparative Morphology of Some Leguminosae

Abstract

Features common to the five species are as follows: (1) campylotropous ovules; (2) two integuments, the outer preceding the inner; (3) a multicellular archesporium; (4) one parietal cell cut off which gives rise to more or less parietal tissue; (5) the production of a row of 4 megaspores; (6) the rapid destruction of nucellar tissue which brings the embryo sac in contact with the inner integument; (7) antipodals ephemeral. Contrasting features are as follows: (1) the number of ovules is always 2 in Trifolium pratense, but more than 2 and various in the other species; (2) the third megaspore sometimes functions in T. repens; (3) in Trifolium the embryo sac rapidly destroys the antipodal end of the nucellus and thus forms a long tubular sac; (4) in Trifolium the embryo sac remains very vacuolate, while in Vicia and Medicago the sac fills with cytoplasm; (5) polars meet on median line or on inner side of sac in Trifolium, but rest near the egg apparatus; in Medicago the polars meet near the center of the sac and rest near the egg apparatus; while in Vicia they meet on the inner side of the sac and remain some distance from the egg apparatus; (6) in Trifolium and Vicia, the starch appears in the micropylar end of the nucellus and in the inner integument, while the starch fills the sac in Medicago; (7) in Trifolium the proembryo is short and massive and no definite line between suspensor and embryo was made out; more evidence of the separate parts was seen in the more slender proembryos of T. hybridum and T. repens; (8) definite suspensors with multinucleate cells appear in Medicago sativa and Vicia americana; in the former species the suspensor is filamentous, but composed of two superimposed pairs of cells in the latter species; (9) sterilization is most marked in T. pratense.