MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 24I 



lions of the shoot or crown, being approximately the same as in 

 juvenile sprouts arising from the base of trunks. The etiolated 

 branches failed to develop beyond a certain 3'oung condition although 

 their existence extended over a period of five months, which is fully 

 equal to the entire vegetative season of the tree. None of the branches 

 grown in darkness succeeded in accomplishing such differentiation 

 and development of tissue as to allow them to pass into permanent 

 form, all of the etiolated twigs dying back to the old stems at the end 

 of their period of activity. Unlike Acer, branching occurred with 

 normal frequency, but the branches, both primary and secondary, 

 assumed an erect attitude in darkness, due to an alteration in the 

 geotropic properties, or to the lack of the phototropic stimulation in 

 response to which the branches habitually assume an approximately 

 horizontal position in light. 



The length, number and length of internodes, and diameter of 

 etiolated branches of Populics were greater than in normal branches, 

 no comparison having been made with juvenile sprouts. The primar}'- 

 branches assumed a position approximatel_v horizontal in some in- 

 stances, and the secondary branches which were produced in some 

 profusion were more or less nearly erect. The branches grown in 

 darkness were of comparatively brief duration and did not succeed 

 in making such development of tissues as to pass into permanent 

 form, dying back to the base in a few weeks. 



The etiolated twigs oi Rhus did not exceed the normal in length, 

 number and length of internodes, or diameter. No branching was 

 observed in the single specimen grown in the dark room, and the 

 blanched members soon perished, their duration being much less than 

 that of a vegetative season. 



The records of etiolations of entire trees by previous investigators 

 are extremely meager. J. A. Hill writes in 1759: "The growth of 

 plants, at least their regular growth, as well as their absolute life 

 depends not only on warmth and moisture, but on light ; this moves 

 their juices, and upon this motion greatly depends their increase. If 

 tender plants be kept in constant darkness they lose their leaves and 

 die. Thus Mr. Lee, of Hammersmith, at my desire, making the 

 experiment most fairly, killed tw^o tamarind trees and an abrus ; and 

 would have killed an erythrina, but he gave it light in time and re- 

 covered it. Light keeps the juices in motion ; and this preserves the 

 whole. When it is not admitted these stagnate, and they ferment 



