618 LECTURE XXII. 



Sorokin as occurring in two plants, Tetrachytrium and Haplo- 

 cystis, which probably belong to the Chytridiaceae. 



It is of interest to note that in various Mucorini (Absidia 

 septata and capillata, Mucor fusiger, Sporodinia, always in 

 Mucor tennis) and Entomophthorese (Entomophthora radicans, 

 and various species of Empusa) we have well-marked instances 

 of sexual degeneration. Spores, exactly resembling the 

 zygospores, are produced parthenogenetically by the repro- 

 ductive organs. In some cases the reproductive organs are 

 produced, and come into relation, but no fusion, no sexual 

 process takes place, but each produces a zygospore independ- 

 ently. In other cases an isolated reproductive organ produces 

 a single zygospore. These parthenogenetically produced 

 spores are termed azygospores. 



In Protomyces and the Ustilagineae a peculiar mode of conjugation 

 has been observed. Certain reproductive cells of an elongated form, 

 termed sporidia^ are produced, and these become connected in pairs by a 

 transverse canal, so that they then resemble the letter H. No zygospore 

 is formed, but the H-like body is its equivalent. The question of the 

 sexual nature of this process is still under discussion, but it is made 

 probable by the fact that in all fully investigated cases the sporidia 

 are incapable of independent germination, a fact which, if fully estab- 

 lished, would prove them to be sexual reproductive cells. But against 

 this there is to be set Fisch's observation that the nuclei of the conjugating 

 sporidia apparently do not fuse. 



It is in the group of Fungi which we may term the Oomy- 

 cetes, that the sexual process attains its highest development 

 in the Fungi. In the Ancylisteae, which may be regarded as 

 the lowest form of this group, the sexual process shews but 

 a slight advance on that obtaining among the Zygomycetes. 

 It is true that the two sexual organs differ from each other in 

 external appearance, the female organ, here termed an 

 oogonium, being relatively large and expanded into a bulbous 

 form, whereas the male organ, the antheridium, is filamentous 

 and relatively small. In the sexual process the whole of the 

 contents of the antheridium pass over as a gamete into the 

 oogonium and fuse with the whole of its protoplasm, the 

 product being an oospore. It may be incidentally mentioned 



