2'2i\ 



Plant Tissue Culture 



PIG. 71. Two sister cultures of Nicotiana Callus tissue. That 



above was grown for _<> weeks on :i semi-solid medium providing 

 adequate aeration. Thai below was grown for !<• weeks on the 



semi solid medium followed by 10 weeks in ;i nutrient of the same 



constitution except for the omission of the agar. Here the culture 

 was submerged and thus subject to reduced aeration, stem grow 

 ing points and Leaves of n high order of differentiation have, under 

 the latter conditions, developed from n tissue mass which, on the 

 semisolid nutrient, appeared to have lost the capacity to differ- 

 entiate. <1.5. (From White, P. R. L939. Bull. Torrey Bot. Club 

 66: 509, fig. 1, 888. i 



