BACTERIA. FUNGI. 169 
“honey-combed ringworm”, and named Favus by doctors; dandruff (Pityriasis 
versicolor) is produced by Microsporon furfur, and Herpes tonswrans by Trico- 
phyton tonswrans. The latter has a remarkable effect on the hair, causing it to fall 
out and leave the part of the skin affected bald. 
Water-plants are attacked by parasitic fungi comparatively rarely, which is the 
more noteworthy because such large numbers of non-parasitic epiphytes settle upon 
the filaments of green alge, and on the brown Fucoides, and red Floridex. Minute 
Fig. 33—Parasites on Hydrophytes. 
1, 2, and 3 Lagenidiwm Rabenhorstii. 4,5 Polyphagus Euglene, ® Rhizidiomyces apophysatus. 
forms of fungi, invisible to the naked eye, and belonging to the Chytridew and 
Saprolegnie, are parasitic upon green algal filaments, especially on the fresh-water 
species of the genera (Edogonium, Spirogyra, and Mesocarpus. One of these 
microscopic parasites is represented in fig. 33»%°, and bears the name Lagenidiwm 
Rabenhorstii. It develops non-ciliated, spherical swarm-spores, which lay them- 
selves upon the walls of Spirogyra-cells, perforate them, and insert a club-like 
process. The protuberance forthwith becomes a tube, which increases rapidly in 
size in the interior of the cell, ramifying and completely destroying the bands of 
chlorophyll. The branched tubes of Lagenidiwm reproduce themselves in two 
ways at the expense of the host’s cells infested by them: they form on the one 
hand so-called oospores by means of fertilization, and on the other sporangia. The 
latter process is clearly shown in fig. 334%%. In this case, one of the tubular 
