ZYGOMYCETES 347 



growth in amoeboid fashion, a cell-wall is secreted, and each becomes a 

 zoosporange. Swellings arise on the mycele of the host as the result of 

 this parasitism. The zoosporange then sends forth a cylindrical process, 

 which perforates the wall of the Saprolegnia, and through it the zoospores 

 are discharged. The zoosporanges are either smooth and capable of 

 emission of zoospores at once, or are covered with fine spines and capable 

 either of emission at once or of resting. While the latter are generally 

 formed under adverse circumstances, it seems to occur with some regu- 

 larity that the zoospores of the smooth zoosporanges give rise to spiny 

 zoosporanges, and vice versa. The life-history of these two species may be 

 taken as typical, and the incompletely-known species of Olpidium (A.. Br.) 

 doubtless conform to it. 



Sub-order 4 : SYNCHYTRIE^E. The Synchytriese inhabit the epiderm 

 of terrestrial Flowering Plants, in which they excite the production of 

 small yellow or dark-red galls, owing to the abnormal swelling of the 

 epidermal cells affected. Like the Olpidieae, they have no mycele, but 

 they are distinguished from that sub-order by the formation of a sorus 

 of zoosporanges. From the germinating zoospore an initial cell is formed, 

 the contents of which break up into a sorus of zoosporanges. In 

 Pycnochytrium (de By.) ( = Chrysochytrium, Schroet., and Leuco- 

 chytrium, Schroet.) the initial cell is a resting-cell, which eventually 

 germinates by the gradual protrusion of its contents into a globular sac 

 seated upon the extine. Within this sac the sorus of zoosporanges is 

 formed by the division of the protoplasm. Each zoosporange pro- 

 duces a considerable number of zoospores, which again give rise to 

 resting-cells. In Eusynchytrium (Schroet.) an indefinite number of 

 sorus-forming generations, which at once produce zoospores, intervene 

 between resting-cell and resting-cell ; while in Synchytrium Taraxaci 

 (deBy.) the resting-cell produces a zoosporange without the intervention 

 of a sorus, a process suggestive of the Olpidieas. No conjugation of 

 zoospores nor any sexual process has been observed in any member of 

 the group. 



W T oronina and Rozella, which inhabit Saprolegniese, may be placed 

 with Synchytrieae. 



De Bary (loc. at., p. 170) treats as doubtful Chytridiaceas (i) Tetra- 

 chytrium triceps (Sorok.), the zoospores of which are said to conjugate; 

 and (2) Hapalocystis mirabilis (Sorok.), the zoospores of which are 

 described as conjugating within the mother-cell. The observations, 

 however, require confirmation. 



Beyond the general reference to Professor de Bary's ' Comparative 

 Morphology,' &:c., the student is specially referred to that source with 

 regard to this incompletely-known group. 



