330 PRACTICAL COURSE IN BOTANY 
curled, giving them a somewhat leaflike appearance, whence 
they are called “foliaceous ” lichens. This broad, expanded 
body is the thallus, or vegetative part, as distinguished from 
its reproductive part. Examine carefully the thallus of 
your specimen. Note the size and shape of the indentations. 
Is there any order or regularity about them, such as was 
observed in the lobing of leaves? Is there any difference 
in color between the upper and under sides? What other 
differences do you notice? Do you see anything like hairs, 
or rootlets, on the under side? Mount one of them in water 
and place under the microscope. What does it look like? 
Compare with one of the hairs from a leaf of mullein, grom- 
well, blueweed, or other hairy plant, with the hypha of a 
fungus mycelium, and with your study of the root hair in 
67 (a). Is it a hair or a root? These rootlike hairs are 
called rhizoids, and serve to anchor the lichen to its substra- 
tum. Look on the upper side for little cup-shaped or 
saucer-shaped receptacles. On what part of the thallus 
are they situated? Ex- 
amine with a lens and see 
if you can make out what 
they contain. These cups 
are the spore cases. The 
lichen fungus belongs to 
the division of sac fungi, 
which produce their 
spores in closed sacs, or 
cups. 
Po, 70.— Porn of eis schon, 389, Structure of the 
thallus. — Make a thin 
section through a thallus and place under the microscope. 
Notice the small green bodies enveloped in the hyphe of the 
fungus. Are they most abundant near the upper or the lower 
epidermis? Has their green color anything to do with this, 
and with the difference in color between the two surfaces of 
the thallus? (184.) Do they look like chlorophyll granules ? 
