MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 259 



year or more in darkness. The ample supply of reserve material 

 still available in the endosperm demonstrated, that in such instances 

 the development of the leaf was not primarily, or directly, due to lack 

 of constructive material, although some influence might be ascribed 

 to the failure to make such material locally. Peltandra (p. 144) de- 

 veloped leaves in darkness the petioles of which were not much 

 longer than the normal and were somewhat thinner. The laminae 

 were only partially extended, being much smaller than normal organs. 

 Functional stomata were present but the leaves were of briefer dura- 

 tion than others grown in light. The etiolated leaves of Trillium 

 (pp. 181, 182) did not attain normal expansion, the sessile laminae 

 being held in an appressed position around the terminal flower bud. 

 The tests of the two species of this genus were made under some- 

 what doubtful and faulty conditions, however. 



It is to be seen that leaves of monocotyledons with an open, 

 netted, or feather arrangement of the veins do not expand the lami- 

 nar portions during growth in darkness, and that the petioles when 

 present are excessively elongated. Sessile leaves, as in Trillium^ 

 do not undergo any undue lengthening of the basal portions of the 

 laminae. The striking difference in behavior between these plants, 

 and the species bearing leaves with a strictly parallel arrangement of 

 the veins suggests that the amount of growth accomplished by leaves 

 of monocotyledons arising from plants confined in darkness may be 

 dependent upon the location of the growing zones, and upon the 

 mechanical position of the tissues in which an abnormal differentia- 

 tion and development takes place. It is evident however, that no 

 generalizations may be maintained as to the behavior of leaves of 

 monocotyledonous plants as distinguished from dicotyledonous forms, 

 since the reaction of any leaf to darkness seems to depend upon 

 structural causes to some extent, and is not conformable to any phylo- 

 genetic features of the species involved. This is further illustrated 

 by the influence of darkness upon various types of leaves of dicoty- 

 ledonous plants. 



Effect of Etiolation on Leaves of Dicotyledons. — A group of 

 species in which the leaves arise from subterranean stems or bulbs 

 offer suflncient similarity in the more general features to warrant a 

 separate consideration. The following may be included : Bicuculla 

 (p. 80), Cicuta (p. 93), Cyclamen (p. 100), Hydrastis (p. 117), Oxalis 

 (pp. 137, 141), Pastinaca (p. \iif'T^^ Podophyllum (p. \yS)^ Rheum (p. 



