164 DIVISION II. — COURSE OF DEVELOPMENT OF FUNGI. 



in this place. It is evident that we have before us an intermediate case between the 

 ordinary forms of oogamous and isogamous conjugation. 



Besides a second species of Polyphagus, exactly like P. Euglenae, which attacks 

 Conferva bombycina and is called by Nowakowski P. parasiticus, there are a number 

 of Chytridieac which appear to belong to the type of P. Euglenae. Among the first of 

 these, according to Schroter's brief communication (1882), is Physoderma pulposum, 

 YYallr., a plant endophytic in the Chenopodiaceae, and with some highly peculiar 

 characters about which we await fuller information. Another in all probability is 

 Rhizidium mycophilum which inhabits Chaetophora elegans, and, according to 

 Nowakowski's account, and putting aside some variations in form which we may at 

 present disregard, is entirely like Polyphagus Euglenae in all important points of 

 structure and development ; we do not indeed know the formation of the rcsting-spores, 

 but their germination is the same as in Polyphagus. Then there are a number of 

 forms described under the names Rhizidium and Rhizophydium (with Obelidium 

 of Nowakowski), most of them parasitic on larger Algae, in which as in Polyphagus the 

 body of the germinating swarm-spore puts out rhizoids and grows into a swarm- 

 sporangium, and in which mature resting-spores of unknown origin have been found here 

 and there. These Rhizophydieae also, from the account which we have of them, require 

 further examination. Finally we may class with those already mentioned a number of 

 A. Braun's typical Euchytridieae and Phlyetidieae which live in Algae, since they 

 resemble them in structure, and their rhizoids were overlooked by the older observers on 

 account of their great delicacy. How far this is the true view of their affinity must be 

 determined by further research, which, if I am not misled by imperfect observations, 

 requires to be extended even to the most typical Euchytridieae such as Chytridium 

 Olla. 



I add what follows in justification of this remark. Chytridium Olla, A. Br., is parasitic, 

 as Braun tells us, on the unripe oospores of Oedogonium rivulare and kills them. Its 

 swarm-spores settle according to Kny's description on the orifice of the oogonium which 

 is filled with mucilage, put out slender rhizoid- processes from thence towards the 

 oospore suspended in the oogonium, and then convert their body which is outside the 

 oogonium into a sporangium ; the rhizoid-process becomes a thick cylindrical stalk by 

 means of which the sporangium is attached to the oospore, and which is delimited from 

 the sporangium by a transverse wall when the development is complete. I am inclined to 

 doubt whether the rhizoid-process or stalk of the sporangium proceeds from the cilium of 

 the swarm-spore, as Kny states, because this is never the case in other species of similar 

 growth, though there is often the appearance of it ; I have never examined into this 

 point in Chytridium Olla. The swarm-sporangium is ovoid in shape when fully grown, 

 and when it discharges its spores it throws off the apical portion of its membrane like a 

 small lid, as is shown in Fig. 76 A, B. According to the reports of observers the stalk 

 is attached firmly to the surface of the oospore by its obtuse extremity only ; but when 

 attempting to detach it I often saw the extremity prolonged into a little point which seemed 

 to pierce through the membrane of the oospore, but could not be followed into its interior. 

 My material was very old when I undertook the investigation, and the sporangia 

 of the parasites on the oogonia were already emptied of their contents, and it was 

 quite possible that rhizoid-processcs might have penetrated into the oospore at an 

 earlier stage but have disappeared in the decomposed contents of the oospore at the 

 time of the investigation. 



In older cultivated plants of Oedogonium which have been attacked by Chytri- 

 dium Olla we often find a great many oospores of the Alga, which were killed by 

 the parasite while still young and when their walls were still thin, and inside them 

 in their decomposed cell-contents colourless glistening round bodies usually in large 

 numbers. These when carefully examined (Fig. 76 A) and isolated (Q prove to be 

 thick-walled spherical cells containing a dense strongly refringent central sphere of 



