1 68 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



room in November, 1901. Two buds near the base of the young 

 inclined stem soon awoke and formed stems 15 and 25 cm. in length. 



These etiolated stems 

 were twice the thickness 

 of the normal, due to the 

 exaggerateddevelopment 

 of the cortex and the 

 internodes were longer 

 than the normal. The 

 leaves did not go beyond 

 the stage described 

 above. (Fig. 127.) 

 Rheum sp. 

 Rootstocks of rhubarb 

 obtained from a dealer 

 were placed in a dark 

 chamber in the early part 

 of March and sent up 

 leaves in which the peti- 

 oles were both thicker 

 and longer than the nor- 

 mal. The branches of 

 the petiole in the laminar 

 portion of the leaf separ- 

 ated but slightly, and in 

 so doing ruptured the in- 

 active lamina in many 

 places, a phenomenon 

 also observed in the re- 

 1 a t e d genus Rtimex. 

 Such etiolated leaves 

 elongated at a fairly con- 

 stant rate, the minimum 

 being shown about 10 

 A.M. It could not be as- 

 certained from the study 

 of the auxanometric data 

 whether this resulted 

 from a true rhythm or 



Fig. 129. Etiolated leaf of Rheum, ]/^ actual size. 



