i68 



DIVISION II. COURSE OF DEVELOPMENT OF FUNGI. 



is gradually becoming finely granular, it divides into the numerous sporangia which 

 form the sorus (c, ct). The swarm-cells (g) discharged from the sporangia become new 

 resting-cells, if they find a host. This is the history, for example, of Synchytrium 

 Mercurialis, S. Anemones, &c. The course of development in the Eusynchytrieae 

 is somewhat different; an unlimited number of generations of sori may be and 

 actually are interpolated between every two successive hybernating generations 

 of resting-cells; these sori are formed from swarm-spores without there being 

 any resting period and produce again new swarm-spores. The spore which has 

 penetrated into the swelling cell of its host developes into the thin-walled initial cell, 

 which divides into the members of the sorus as soon as it has reached a definite stage 

 of development. After a number of such generations have been produced, partly 

 perhaps owing to external causes, the formation of resting-cells recommences. The 

 behaviour in germination of these also varies in different species; in some, as for 

 instance Synchytrium Stellariae (Fig. 78) and S. Oenotherae, they form sori like 

 those of the Pycnochytrieae ; in others each resting-cell becomes a single sporangium 

 directly without forming sori, as in S. Taraxaci. 



FrG. 78. Synchytrium Stellariae, Schrb't., from Stellarta media, ad germination of the resting-cells when placed 

 in water after hybernating in the dry state, a c successive states of the same specimen, * four hours later than a, c seven days 

 later and five days after division into the cells of the sorus. d a mature sorus with the mature sporangia falling asunder, e g a 

 single sporangium in water, e immediately after being taken from the sorus. /"the same two hours later shortly before formation 

 of spores, the small sphere of fatty substance being divided into parts of equal size, g forty-five minutes later with the swarm- 

 cells escaping, a <i magn. 145, e s 375 times. 



It is obvious that the difference between the Synchytrieae and the group of the 

 Olprdieae lies in the formation of sori. Species like Synchytrium Taraxaci with 

 resting-cells which become sporangia without dividing are to some extent intermediate 

 forms. Neither conjugation nor any sexual process has been observed in either group. 

 From the facts before us we can only gather that a sorus or resting-cell proceeds 

 directly from a swarm-spore. Influenced by the analogy of the isogamous Algae and 

 Protomyces, I sought carefully in Synchytrium Stellariae and S. aureum for the con- 

 jugation of free swarm-cells, but, as was the case in my examination of Cladochytrium, 

 I never found an instance of it, either between spores of one or of different sporangia 

 belonging to the same or to different sori. The abnormally large swarm-cells which 

 are observed occasionally with two or more spheres of fatty matter and additional 

 cilia are monstrous forms and not products of conjugation. These negative results 

 do not preclude the possibility of conjugation ; it might occur inside the cell of the 

 host if more than one swarm-cell had found its way there. Cornu is inclined to 

 account in this way for the formation of the resting-cells of Synchytrium, but he 

 adduces no decisive observations in support of his view, but only an arbitrary com- 

 parison of states of S. Stellariae found side by side. The objections to this are 

 so obvious that they need not be specified. Direct observation of the development 



