792 The American Naturalist. [September, 
2. Diagrammatic longitudinal section of Robinia pseudacacia. 
a. Cork layer. The cells are more irregular than those of the 
root. c. Vascular system. d. Infected area. e. noninfected 
areas. 
3. Same as 1, but without the “ Infektions füden " and show- 
ing the cell entirely filled with the much modified Rhizobium 
mutabile. Nuclei are much enlarged and nucleoli show dis- 
tinetly. 
4. b. Much modified Rhizobia mutabilia with highly refractive 
bodies c. a. Starch granule which is capped by the empty 
case of a Rhizobium, b. 4. A starch granule just forming 
inside of a partially empty Rhizobium case. a. Some free 
starch granules. 
5. Cross section of a vascular bendi. a. Sheath. b. Phloem. 
c. Vessels. 
