THALLOPHYTES : FUNGI 
285 
"been discovered. The life history seems simple, but this 
apparent simplicity may represent a very complicated his- 
tory. The structure of the common mushroom (Agari- 
cus] will serve as an illustration of the group (Fig. 255). 
190. A common 
mushroom. The Jjffl , I 
. ^aSOTlUUll/flkts^ LA, / . /TS /?*. /fJ 
mycelium, 01 wmte 
branching threads, 
spreads extensively 
through the decay- 
ing substratum, 
and in cultivated 
forms is spoken of 
as the " spawn." 
Upon this myce- 
lium little knob- 
like protuberances 
begin to arise, grow- 
ing larger and 
larger, until they 
are organized into 
the so-called 
" mushrooms." 
The real body of 
the plant is the 
white thread - like 
mycelium, while 
the " mushroom " 
part seems to rep- 
resent a great num- 
ber of sporophores 
organized together 
to form a single 
complex spore- 
bearing structure. 
The mushroom 
FIG. 256. A common Agaricus : A, section through one 
side of pileus, showing sections of the pendent gills; 
B, section of a gill more enlarged, showing the cen- 
tral tissue, and the broad border formed by the ba- 
sidia : C, still more enlarged section of one side of 
a gill, showing the club-shaped basidia standing at 
right angles to the surface, and sending out a pair 
of small branches, each of which bears a single ba- 
sidiospore. After SACHS. 
