MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 219 



At the end of this period half of the material originally stored still 

 remained in a normal condition, and it seems entirely probable that 

 the seedling of this species might be capable of living two or three 

 years in total darkness, receiving only water and mineral salts from 

 the substratum. No evidence has been afforded by my experiments 

 that any adaptation to continued darkness, was made by an increased 

 capacity for taking up organic matter from the soil. 



Continuous growth resulting in the formation of a number of 

 leaves far in excess of that shown in an ordinary season, was 

 observed in Canna, which developed etiolated leaves vigorously and 

 continuously for four months. Caladhi?n (p. 85), which continued 

 sending up leaves for a period of twenty months in darkness before 

 the underground member perished, and Rumex (p. 170), which sent 

 up a succession of leaves for eight months are also examples of this 

 type. The slow growth of succulents in darkness is of a similar 

 character. Opuntta (p. 131), makes a steady extension of the 

 curious cylindrical etiolated shoots through long periods of dark- 

 ness. Gasteria (p. no), was found to continue the extension of 

 its aerial shoot for eighteen months in total darkness, and Sanse- 

 vieria (p. 171) for a period of twenty months, by means of food 

 stored up in the underground stems and succulent leaves. 



The endurance of plants which undergo seasonal periods of in- 

 activity in darkness gives the question a new aspect. In one series 

 inclusive of Apios (p. 42), Aristolochia (p. 71), and Cyclamen (p. 

 100), shoots are sent up from the tuberous underground organs 

 which undergo a characteristic etiolative development, and then 

 perish, the plastic contents of the newly formed members being 

 transported back into the storage organs. At the close of the sea- 

 son, the amount of material in such organs is less the amount used 

 in respiration, and the portion that has been converted into aplastic 

 substances in the aerial organs. The principal changes in the storage 

 organs of plants of this type consist in slow increases in size during 

 a number of seasons until destroyed by some contingency, or reach 

 some limit of growth at present unknown. The external layers 

 of such members are generally well protected by corky or other re- 

 sistant layers, and do not decrease in size during the withdrawal of 

 the material necessary in the construction of the aerial shoots. 



A larger group of the species brought under observation have 

 underground organs in the form of rhizomes and corms in which a 



