CHAPTER VII.—PHENOMENA OF VEGETATION.—LICHENS, 395 
The Chytridieae of the genera Rozella and Woronina, which were discovered 
by Cornu and more thoroughly examined by A. Fischer’, are parasites on the stout 
tubes of the Saprolegnieae which are destined to form spores (see Figs. 68 and 69). 
Rozella septigena, Cornu lives on species of Saprolegnia. Its swarm-spores are 
ellipsoidal in shape and 6-8 » in length, and bore their way into the growing tubes 
of Saprolegnia. When a spore has effected an entrance in this way, it remains 
visible for a short time in the protoplasm of the tube and then can no longer be 
distinguished; it seems to lose its individuality, to distribute itself and be lost in 
the protoplasm of the tube. The tube at once swells out as a large quantity 
of fresh protoplasm streams into it, and it divides by transverse walls formed 
for the most part in basipetal succession into swollen cylindrical or barrel-shaped 
segments, which are from two to several times longer than broad (Fig. 166). The 
transverse walls are formed in the same way as in the delimitation of sporangia 
in Saprolegnia. Then the protoplasm in each segment becomes invested with 
another special membrane lying in close contact with the first and thus the cell 
becomes the sporangium of a Chytridium (see section XLVI). About 60-80 hours 
elapse between the entry of the spore and the emptying of the sporangium. The 
process is the same if more than 1 spore has entered the tube of the Saprolegnia ; 
when a single spore entered 2-14 sporangia were observed to be formed, 21 
sporangia when 4 spores entered the tube. Rozella appears to form resting-spores 
when many of its swarm-cells have made their way into the Saprolegnia. In this 
case also the swarm-cells entirely disappear in the protoplasm of the host, which 
then puts out stalked spherical branches resembling the oogonia of Saprolegnia, and 
a resting-spore is formed from the protoplasm of each branch (Fig. 166, s). The 
phenomena observed in Woronina are quite similar to those in Rozella apart from 
certain differences in the form of the parts. 
If no later investigations bring to light facts at variance with those here given, 
and this according to Fischer’s statements is not probable -but cannot however be 
considered to be impossible, the above case is an instance of a parasite surrendering 
its individuality, so far as that can be recognised morphologically, after its entrance 
into the host; it becomes changed into a part of its host, and the two can no longer 
be distinguished from one another by our present means of investigation. The 
parasite also communicates new properties to the host which is some two hundred 
times its. size, and through them the host developes into its own parasite. This 
transmutation of the host by the parasitic spore which has coalesced with it, though 
peculiar, is yet analogous with the fertilising effect of the spermatozoid on the 
oosphere of organisms which in the sexual sense are highly differentiated from one 
another. 
Fungi which form Lichens. 
Section CXIV. A large number of species of parasitic Fungi employ Algae 
as their hosts, either unicellular Algae which live isolated, or pluricellular Algae, 
or Algae which unite together in gelatinous colonies. The germ-tube of the Fungus 

} Ueber d. Parasiten d. Saprolegnieen. See also citations on page 171. 
