MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 221 



repeated growth is a most effective device in the economy of species 

 living in regions in which the upper layers of the substratum is 

 loose and subject to shifting changes which might cover a plant too 

 deeply for it to reach the surface during any given season. It is to 

 be seen that Arisaema (pp. 48, 50) is capable of four distinct efforts 

 to reach light and exposure to atmospheric factors. The seedlings of 

 this plant exhibit this same adaptation in a remarkable degree, since 

 the plantlet is capable of three seasonal efforts to bring its develop- 

 ing leaves up into sunlight. As has been described previously, 

 Arisaema Dracontium (p. 48) and Arum maculatum naturally carry 

 on the first season's growth of the plantlet without the development 

 of chlorophyl-bearing organs, thus greatly lengthening the period 

 of saprophytic nutrition of the seedling. ^""^ 



A fourth type of endurance to prolonged periods of darkness is 

 offered by species in which the old storage organs are destroyed 

 during the period of formation of aerial organs from their buds, and 

 new subterranean organs are developed on branches of the original 

 organ or from lateral buds from the stems arising from them. 

 Aplectrum (p. 46), Bicucidia (p. 80), Solaniim (p. 180) and Tipii- 

 laria (p. 181) may be cited as examples. The total duration of no 

 one of these species has been tested, but the potato has been seen to 

 form the second generation of tubers in darkness, and doubtless this 

 species is capable of extended existence without light under proper 

 conditions of temperature and moisture. In addition to the simple 

 behavior of the corm in Arisaema (pp. 48, 50) noted above, the lateral 

 buds may develop young corms and use up the material from the 

 parent corm, continuing the existence of the plant in this manner. 



It is to be seen therefore that an exposure of the aerial members 

 of a plant to light is not an indispensable tonic condition for the 

 plant. The subterranean members may continue their normal ac- 

 tivity for several seasons when deprived of illumination, and with 

 but little alteration in their structure, and that due directly to the 

 amount of reserve material returned from the perishing etiolated 

 members. In a few examples creeping stems which are only par- 

 tially submerged or imbedded in the soil undergo changes in habit 

 and function when placed in darkness, but such reactions must be 



'^° MacDougal. Seedling of /4;-/.<rt<?;«rt. Torreja, i : 2. 1901. 



Rennert, R. J. Seeds and Seedlings of Arisaema triphyllum and Arisaema Dra- 

 contium. Bull. Torr. Club, 29: 37-54. 1902. 



