214 



Plant Tissue Culture 



Fig. (>."). Transverse section of an 8-weeks-old culture of 

 Vicotiana callus, showing the compact, relatively organized central 

 portion surrounded by a broad region of younger, louse, unorgan- 

 ized, and mostly rapidly growing tissue. 20. (From White, P. 

 R. 1939. Am. J. Hot. 26: 61, fig. •"".. 78.) 



I'm. (i(i. Detail from Lower margin of Pig, !>."">, showing meriste- 



matic areas scattered through the upper half of the picture while 



the lower portion, particularly at the left, is made up largely of 

 gianl cells of a mature type, x 138. (From White, 1'. R. L939. 

 An,. .1. Bot. 26: til', fig. 7, 78.) 



