MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 215 



solid tubers and corms like Aristolochia (p. 71), Artsacma (pp. 48, 

 50), Calla (p. 87), Caladium (p. 85), Peltandra (p. 144) and others 

 of this type, the newly-formed part of such structures being more 

 slender when formed at the bases of etiolated branches, inflores- 

 cences and leaves. In the last-named instances, however, in addi- 

 tion to having a lessened need of storage tissue the etiolation of the 

 aerial organ undoubtedly exerts an additional stimulation by which 

 more attenuated forms result. This action is the converse of that 

 seen in partial etiolations in which illuminated organs exert a stimu- 

 lative effect on others in darkness. The former phase of the reaction 

 is most highly accentuated in Aj)lecirum (p. 46) and Tiptila^'ia (p. 

 181) of the plants studied. In these two species the vegetative sea- 

 son is characterized by the formation of one or more offsets from the 

 corms, the terminal internodes of which become apogeotropic, as- 

 sume an upright position and become thickened into a corm, bearing 

 a single leaf from the uppermost internodes. The leaves are much 

 longer than the normal and do not completely expand, remaining in 

 a plicately folded position in the darkness. This attenuation is also 

 participated in by the internodes from which the corm is formed, a 

 length nearly double that of the normal being reached, with a diam- 

 eter less than the normal (Fig. 161). 



The creeping rhizome of Sansevieria offers an example of a 

 diageotropic stem which undergoes alterations in its geotropic proper- 

 ties during etiolation, becoming apogeotropic and assuming an up- 

 right attitude, the structure becoming entirely radial (p. 171).'^^ 



A similar action is exhibited by Nti^har hiteiini according to 

 Goebel, the creeping rhizome assuming an erect position, and 

 undergoing alteration from a dorsiventral to a radial structure when 

 covered with earth ; the effect in question is ascribed to darkness, 

 and is said to be exhibited by many spermatophyta.^^* 



Effects of Etiolation on Aquatics. — The photomorphotic relations 

 of rooted and submerged aquatic plants are by no means simple, and 

 reactions are so highly diverse that a general treatment is all but im- 

 possible. The stems or modified branches bearing floating organs 

 of Nti^har, Nymfhaea^ and other species which anchor to the sub- 

 stratum have been shown by Frank to have a capacity for adapta- 



'^^Maige, A. Recherches biologiques sur les plantes rampantes. Ann. Sc. Nat. 

 Bot. Ser. 8, 11 : 345. 1900. 



15* Goebel, G. Organography of Plants. Part i, p. 231. 1900. 



