CHAPTER V. COMPARATIVE REVIEW. CHYTRIDIEAE. 



165 



B 



fatty matter in a finely granular protoplasm tightly packed in a vesicular receptacle, 

 which was evidently an intercalary member of a very slender branch filament. The 

 spherical cells rich in fatty matter are resting-spores of Chytridium. After a long resting 

 period (about four months in the cases which have been observed) they germinate and 

 put forth a cylindrical germ-tube, which as it grows takes the shortest way to reach the 

 outside, piercing through the membranes of the oospore and the oogonium. When its 

 extremity has reached the outer surface of the oogonium, it swells into an ovoid spo- 

 rangium, which resembles in every respect that which is ascribed to Chytridium Olla. 

 It is developed at the expense of the protoplasm of the resting-spore, which passes 

 through the germ-tube into the sporangium after the dissolution of the fatty sphere ; before 

 this transference has come to an end a transverse wall makes its appearance in about 

 the middle of the tube, and the sporangium when fully grown is also delimited from 

 the tube by a transverse wall (Fig. 76 A, B}. 



So much is matter of observation. The gaps in our knowledge of the details are 

 readily descried ; speaking in general terms we may say that the question of conjugation 

 and fertilisation is still unsettled, and that the continuity of the development between the 

 germinating swarm-spore and 

 the filaments which form the 

 resting-spores has not been satis- 

 factorily established. This latter 

 defect would be of very small 

 importance in presence of the 

 perfect similarity between the 

 sporangia developed from the 

 swarm-spores of Ch. Olla and 

 those from the resting-spores, if 

 another form, also a Rhizidium, 

 had not been observed in the 

 plants examined under cultiva- 

 tion, which at least resembles 

 Chytridium Olla in the formation 

 of the sporangia. The sporangia 

 of this species are not as like 

 the sporangia developed from 

 the resting-spores as are those 

 of Ch. Olla, but they always re- 

 semble them enough to make it 

 necessary to be careful in inter- 

 preting the observed facts. 



In conclusion we refer once 

 more in this place to the genus Zygochytrium mentioned on p. 156. 



SECTION XL VIII. 2. Cladochytrieae. A delicate much-branched and widely 

 spreading mycelium resembling the rhizoids of the Rhizidieae forms numerous 

 terminal and intercalary sporangia on its branches, and the germinating swarm-spores 

 give rise to a mycelium resembling the original one. The sporangia of many species 

 are only known in the form of resting-spores. 



The species first determined by Nowakowski in this group inhabit the decaying 

 tissues of marsh-plants and the jelly of Chaetophora. The course described above 

 has been directly observed in them from the germination of the swarm-spores to the 

 production of the next sporangiferous generation. The sporangia are formed in large 

 numbers on the vegetating mycelium and proceed to form their spores at once without 

 passing through a period of rest. 



FIG. 76. Chytridium Olla, A. Br. (?). A oogonium of Oedogonium rivularc 

 with an immature oospore killed by the parasite ; the oospore contains several 

 resting-spores of Chytridium which ripened in October ; three of these spores 

 are seen still unchanged, two have germinated. By turning the specimen round 

 it was seen distinctly that the empty sporangium a was formed from the rest- 

 ing-spore a', and the sporangium b, which is ejecting its contents, from V ; 

 near the mouth of * are the cast-off lid and two zoospores. an isolated 

 resting-spore after germination with the sporangium still undivided, from 

 another specimen. C resting-spore in a receptacle attached to the branches 

 of the filament on which it was formed, prepared from a dead oospore like that 

 shown in A, A, B magn. 375, C 600 times. 



