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403 



may also divide; and, after one or two more epidermal cells have 

 become active, the underlying cortical cells lose their chlorophyll, 

 become less vacuolate, and undergo cell division. (Fig. 104, B, 

 C) These cells continue division and growth so that the large 

 intercellular spaces become occluded. Adjacent cortical cells 



Fig. 104. A-E, transections of hypocotyl showing origin and development of adven- 

 titious buds after plant has been severed below cotyledons : a, four derivatives of a single 

 epidermal cell; co, cortex; ep, epidermis of hypocotyl; Ip, leaf primordia of adventitious 

 bud. (After Crooks.) 



are also activated, and this continues progressively in a centripetal 

 direction until it has reached the endodermis. In this manner, a 

 meristematic zone of compact cells is formed, extending from the 

 epidermal bud primordium to the endodermis. Continued divi- 

 sions of the cells of the primordium, derived from the original 

 epidermal cells, produce a dome-shaped growing point, and this is 

 followed by the rapid formation of two or three leaf primordia. 

 (Fig. io4, D, Ej and Fig. i05.) 



