156 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



superior thickness of the etiolated stems, which showed a diameter 

 nearly 50 per cent, greater than the normal. This increase in size 

 was accompanied by a loss of the winged angles characteristic of 

 the branches during the first season of normal growth. 



Fig. 117. Partial transverse sections of etiolated branch of Populus Simonii. A, 

 epidermis. B, subepidermal region, showing earlier stages of a lenticel. C, cortex. 

 Z>, bast fibers. ^, cambium. ( See Fig. 1 16. ) 



The epidermal and subepidermal layers lack the thickness of 

 wall of the normal, and the hairs were scarcely half the usual size. 

 Lenticels were to be seen in the earlier stages of formation on 

 normal twigs, which were wholly lacking in the etiolated. The 

 greater diameter of etiolated branches was due to the excessive de- 

 velopment of the cortex, which was composed of larger elements with 

 smaller intercellular spaces. The bast and sieve tissue as well as 

 the cambium and xylem all showed arrested, or retarded develop- 

 ment. 



