Embryology ofVeronica serpyllifolia L.
The young microsporangial wall ofVeronica serpyllifolia L. is made up of four layers of cells, the innermost being the glandular tapetum. During later stages the tapetal cells become binucleate, the middle layer breaks down and the endothecial cells acquire band-like thickenings on their tangential walls.
Quadripartition of the microspore mother cells is simultaneous. The pollen grains at the time of release are two-celled.
Development of female gametophyte in the unitegmic, tenuinucellate, hemianatropous ovules conforms to the Polygonum type. An endothelium surrounds the middle part of the mature embryo sac.
The endosperm isab initio cellular and is haustorial. The chalazal haustorium is unicellular, binucleate and tube-like. It comes in contact with the terminal end of the conducting strand of young seed. The micropylar haustorium, made up of two binucleate cells to begin with, becomes a 4-nucleate body after cell-fusion. The extension of this haustorium is intercellular in the initial stages but becomes intracellular in later stages and comes in contact with the conducting strand near the micropylar part of the seed.
Development of the embryo conforms to the Crucifer type. The celld functions as the hypophysis.
The embryological data obtained in the study have been evaluated in the light of previous work in the tribe Digitaleae.