MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



Ill 



Fifteen months after the cuhure began, the leaves, which had 

 reached full development before confinement in darkness, had 

 perished and the leaves formed partially in light and partially in 

 darkness had begun to die at the tips. (See Fig. 69.) The upper 

 internodes showed a successive increase in the length of the inter- 

 nodes, and the leaves were held at various irregular angles. Such 



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Fig. 68. Gasteria disticha. A, partial transverse section of normal leaf. B, par- 

 tial transverse section of etiolated leaf. C, surface view of normal epidermis of leaf. 

 D, surface view of etiolated epidermis. 



positions were partly due to the rupture of the stems near the nodes 

 and also to the sheathing leaf-bases. 



The structural alterations in etiolated leaves were very marked. 

 The epidermal cells of the normal leaf were irregular polygons in 

 surface view, in which but little difference might be seen in the vari- 

 ous diameters. These cells underwent great axial elongation in etio- 

 lated organs, and the outer cutinized layer was notably lacking. The 

 guard cells of the normal stomata are extended outwardly making 



