35 



Plate 1 



Fig. 1. Usnea irichodea showing small fruits along the stalks. 



Fig. 2. Usnea florida with densely bristly stalks and large fruits. Upper circle. 

 Section of the fruit surface of U. florida showing spores in the spore sacks. 

 (As seen in a hasty, thick section.) Lower circle. The same spores com- 

 pared with the greenish cells of Protococcus always present. 



Fig. 3. Usnea barbata. 



Fig. 4. Structure of an Usnea stalk, showing the tough, white core surrounded 

 by a corky outer layer. 



