CRYPTOGAMS 303 
3. Mention some of the ways in which their presence may contribute 
to the contamination of drinking water. 
4, Refer to Exp. 66, and account for the bubbles and froth that usually 
accompany these plants in the water. 
5. Can you suggest any other causes than the evolution of oxygen that 
might produce the same effect ? 
6. Is the presence of these gas bubbles of any use to floating plants? 
II. FUNGI 
343. Classification.— In the fungi the thallus structure 
is greatly modified, appearing usually as a network of fine 
threads called the mycelium 
(pl., mycelia), from a Greek 
word meaning “fungus” 
(869). These plants are 
all, with a few doubtful 
exceptions, parasites or 
saprophytes which contain 
no chlorophyll and are 
incapable of supporting an 
independent existence. 
Biologists are divided as to 
their position in the genea- 
logical tree of life. The 
weight of authority WY 
at present inclines to i 
the view that they are <_< ee 
degenerate forms de- Ss sis <— 
rived from the alge, ey, a 
but they have been ——— 
so modified by their Fic. 482.— A common form of mold; magnified, 
parasitic habits as to showing thallus modified into a fibrous mycelium: 
randar their posi Son u, @, Spore cases; b, mycelium. (After Korr, in part.) 
in the general scheme of life a doubtful one. They repre- 
sent an offshoot, or side branch, as it were, of the great 
evolutionary line, and so may be considered for the present 
as standing apart in a class by themselves. 
