CRYPTOGAMS 353 



Examine 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 algas 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. 



