XIII. ] ABOUT FUNGI. 185 
prolongation, ultimately developed into a sporan- 
gium or ascus, containing many ascospores, This is 
‘termed the “ alternation of generations,’ and is similar 
to the process of reproduction in ferns, previously 
explained. A fern produces spores, one of which 
cerminating, gives rise, not to another fern—but to a 
minute plant called a “‘ prothallus,” which bears anthe- 
ridia and archegonia. The former fertilise the latter, 
and as the result of such fertilisation a bud is formed 
which develops into a perfect fern. 
We have seen that these low forms of fungi increase 
by cell-division, but only in one direction; the cells 
Fic. 139. 
never divide laterally. This we shall find is a char- 
acteristic of all fungi, and we may see by examin- 
ation of a mushroom or toadstool that the thickness 
of their stems is attained by the growth of many 
hyphz side by side. Like Penicillium and Mucor 
these larger plants arise from spores, which on 
germinating give off hyphe, branching and inter- 
lacing to form a mycelium. Fig. 139 illustrates the 
development of an Agaric or Mushroom. A shows 
the mycelium (my) with two little roundish protube- 
rances (/), the future hymenophore, B is a section of 
