DEPARTMENT OF BOTANICAL RESEARCH. 



71 



thermographic diagram as nearly as possible and to make these figures 

 of such size that the use of averaged rates of growth will include the 

 smallest practicable error. Crude as this method may appear in this 

 preliminary form, it is based upon actual procedure, and all of its 

 essentials are capable of correction ; its use at the Desert Laboratory 

 gave the following values for January in three successive years '} 



Responses of Phytolacca decandra to Various Environmental 

 Conditions, by Francis E. Lloyd. 



The species upon which this investigation is based is the familiar 

 poke-weed, Phytolacca decandra, widely distributed throughout eastern 

 North America, and until now regarded as homogeneous taxonomi- 

 cally. Material has been grown in Arizona (at Tucson and at the 

 Montane plantation, Santa Catalina Mountains) and in California, at 

 Carmel, thus affording exposure to marked climatic extremes. The 

 natural absence of this species from both these localities gives hope of 

 answering the question as to its failure to establish itself therein. 



Responses of vegetative organs. — While it has become evident that the 

 now recognized species is not homogeneous as to leaf-structure, it is 

 sufficiently clear that the plant, when introduced into new environ- 

 ment, shows distinct responses in change in leaf-structure, together 

 with alterations in habit. At Carmel the low summer temperatures 

 induce vegetative growth at the expense of fructification, disturbance 

 in growth-rates (resulting in the distortion of leaf-tissues), and in the 

 general metabolism, causing very early a blotchy discoloration passing 

 through yellows to deep crimson. Even very young leaves are affected. 



'See MacDougal: Auxo-thermal integration of climatic complexes. American Jour, of Bot., 

 vol. 1, pp. 186-193, 1914. 



