MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 229 



ever that normally developed organs may form callus when confined 

 in darkness. 



The stems of etiolated climbers have been shown by various 

 authors to be of normal thickness in some instances, greater than the 

 normal in others, and less than the normal in others. Stems of Apios, 

 Art'stolochia, Bozuica, Falcata^ Mcnisfcj-inum, Ibervillea and 

 Sniilax were thicker than the normal. The increase in diameter 

 was due in all instances to an enlargement of the pith b}^ increase 

 in size of the elements, coupled with increase in the intercellular 

 spaces in some cases, and also an increase in size and number of 

 the elements of the cortical parenchyma with material alterations 

 in the form of the cells in both instances. These plants share 

 with all etiolated stems a lack of differentiation and develop- 

 ment of the epidermal tissues. Trichomes were lacking in the 

 etiolated stems of Apios, and were not so numerous on stems of 

 Menispcrmum grown in darkness as on steins grown in light. The 

 epidermal cells of Apios and Falcata were larger in all diameters 

 than the normal, and smaller in Menispermiun. Functional stomata 

 were present in Apios, in increased number in Aristolochia, but were 

 fairly normal in number in Falcata and Menispei'inum. Tissues of 

 purely mechanical function in the subepidermal region and near the 

 pericycle were lacking in development in all instances, while the 

 stele here as in all etiolated stems remained in an embryonic condi- 

 tion. Apios presented a notable instance of the origin of a second- 

 ary generative layer in the pericyclic region similar to subterranean 

 tuber-forming stems, although no other resemblance to these organs 

 could be made out except, so far as the general increase of the paren- 

 ch3^matous tissues might be taken to be of this character. 



Of the two species of tendril climbers examined, Ibervillea only 

 bore these organs, and in a size but little less than the normal. The 

 tendrils of Smilax are borne laterally on the hypopodial portions of 

 the leaves, which appeared in darkness only as bract-like formations 

 with the tendrils represented by minute papillae. The etiolated 

 tendrils of Ibervillea were found to be irritable to contact, and en- 

 circled small rods of wood, but the free portion of the tendril be- 

 tween the engaged tip and the base was not thrown into spirals ; a 

 fact due among other causes to the lack of development of the me- 

 chanical tissues. Sachs found that the tendrils of Ciictirbita not 

 only clasped supports but the free portion passed into the spiral form 



