CRYPTOGAMS 363 
Ixamine the soil and find out if it contains anything upon which they 
could feed. Note the prevalence of shelf fungi on trees. Examine the 
condition of the wood where they grow, and decide in what ways they 
injure their hosts. Notice whether they abound most on healthy or on 
decaying trunks and boughs, and decide whether this is because the 
fungus prefers that kind of host, or whether the injury it does causes 
the decay, or whether both causes operate together. Notice what fungi 
grow on different trees, and study their preferences in this respect. 
3. Observe the different kinds of lichens found in your walks and try 
to distinguish the three classes. Which kind are most abundant in your 
neighborhood? Which least so? Note the situations in which you find 
each kind growing, whether on stumps, trees, rocks, or the ground. Con- 
sider how the alge and fungi aid each other in the different positions; 
could either, for instance, exist independently on bald rocks? Notice on 
what kind of trees the different lichens seem to thrive best and on which 
poorly or not at all, and whether the character of the bark — rough, 
smooth, scaly —has anything to do with their choice of a habitat. ' 
