LICHENS 
325 
LABORATORY STUDY 
Wet a piece of bread, put 
a tumbler over it, and set it 
in a warm place for three or 
four days. Examine without 
the microscope to get the 
general appearance. With 
the microscope note (1) the 
clear, colorless threads 
(hyphae) making up the mass; 
(2) the groups of spore-bearing 
bodies, black and round, on 
the ends of the upright stalks; 
(3) the spores coming out of 
them. 
Li- 
278. Lichens. 
Figure 295. — Common Field PUffball. 
This is in condition for picking when 
the inside is white. (From Murrill’s “ Edi¬ 
ble and Poisonous Mushrooms.”) 
chens (ll'kens) are grayish green plants which look like 
scales. They grow on old fences, rocks, trees, and the like 
and are especially noticeable after a 
rain. A lichen is made up of the 
hyphae of a fungus, which inclose the 
cells of an alga. The algal cells in a 
flat lichen are usually near the top 
and bottom, and the fungus is in the 
middle of the plant. The alga uses 
the moisture which the fungus collects 
and brings to the plant, and, by the 
use of its chlorophyll, makes food, a 
part of which is used by the fungus. 
The latter, after it has become ac¬ 
customed to the alga, cannot live 
apart from it, and the alga, while it 
can live by itself, appears plump and 
prosperous when it is found sur¬ 
rounded by fungal threads. The 
partnership, therefore, seems to be helpful to both plants. 
Such a relation between organisms is known as symbiosis 
Figure 296. — Bit of 
Lichen, Enlarged. 
A, fungal threads ; B, uni¬ 
cellular algae. 
