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 Chytridieae which affear to belong to the type of P. Euglenae. Among the first of 
these, according to Schréter’s brief communication (1882), is Physoderma pulposum, 
Wallr., 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 resting-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 Phlyctidieae 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-processes 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 (C) prove to be 
thick-walled spherical cells containing a dense strongly refringent central sphere of 
