In the development of distinct antheridial and oogonial cells the allied Ancylistineae show close alliances to Pythium and the Oomycetes.
6, The multicellular ascogonium 3, Passage of the antheridial derived by division from the nucleus towards that of the oogonium; the terminal cell oogonium.
De Bary brought forward very strong evidence for the origin of the ascocarp in Sphaerotheca and Erysiphe by a sexual process, but Harper in 1895 was the first to prove conclusively, by the observation of the nuclear fusion, that there was a definite fertilization in Sphaerotheca Humuli by the fusion of a male (antheridial) nucleus with a female, ascogonial (oogonial) nucleus.
Germination of the microspore begins before it leaves the pollen-sac. In very few cases has anything representing prothallial development been observed; generally a small cell (the antheridial or generative cell) is cut off, leaving a larger tube-cell.
Nemalion sp., carpogonial and antheridial branches.
B, Empty antheridium; p, prothallial cell; I, 2, cells of antheridial walls; 3, cap cell.
Lower part of canal, enlarged; o, cavity of canal, surrounded by a sheath of cells, dilated towards the bottom of canal, in which a large pollen-grain is caught; ex, exterior of pollengrain; in, internal group of prothallial or antheridial cells.
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