74 



Growth 



corresponds to the whole embryo itself and thus to the organism in minia- 

 ture. Recent work shows more and more clearly that the apex is an 

 organized system ( Wardlaw, 1953b, 1957a ) with a structure that is not 

 only histologically but biochemically integrated. Before this structure 

 can control development it must itself develop. Growth of the meristem 



z 



o 



>- 



X 



o 



HOURS 



Fig. 4-15. Lupinus alhus, left, and Tropaeolum majus, right. Below, location of A, B, 

 and C pieces in the two shoot apices. Above, oxygen consumption of these three 

 pieces in milliliters of 2 , at successive hours in the apparatus. In Lupinus there is a 

 gradient from A to C but in Tropaeolum the oxygen consumption is greater in B than 

 in A. ( From Ball and Boell. ) 



precedes that from the meristem. The initiation of a meristem may take 

 place in various ways— from the tip of a young embryo, from adventitious 

 buds by regeneration, or from groups of cells or even single cells— but in 

 every case from simple and undifferentiated tissue. 



A study of the origin of meristematic centers within masses of tissue 



