




Igor} TUBER-LIKE ROOTLETS OF CYCAS 269 
chambers occupied by the algae. The presence of the fungi and 
bacteria within the cells seems to retard the nutritive work, so 
that the cells cannot keep pace with those adjacent. This pro- 
duces tension which results in a development of spaces, and by 

Coke 
Fics. 4-10.— a, algae of intercellular spaces; 4, bacteria; c, parenchyma; s, inter- 
cellular spaces of algal zone; #, elongated parenchyma; /, round corky cells; , cam- 
bium of lenticel ; J, hyphae of fungus; ¢, crystal of calcium oxalate. 
Fic. 4. Intercellular spaces of the algal zone. X 120.— Fic. 5. The same. X 190. 
~—Fic. 6. Part of a cross-section, showing a lenticel and a break in the algal zone 
beneath. X 120.— Fics. 7 and 8. Bacteria and rhizobia found in cultures from 
tubercles. XX 1425.— Fic. g. Part of longitudinal section showing beginning of the 
formation of interce!lular spaces of the algal zone, and cells containing hyphae of 
fungus. XX 300.— FIG. 10. Algae found in the tubercle. X 480. 
means of this tension some of the cells are broken, while others 
appear to be broken down by the organisms within them. After 
the algae have gained entrance, their growth and multiplication 
Probably result in still further increasing the size of these 
