Varietäten, Descendenz, Hybriden. — Physiologie, 149 



grains is not selecting froni what is commonly considered the best 

 plants and vice versa. If the plants from large grains produce a 

 better yield, then they must do so by virtue of the increased vigor 

 of the embryo and the increased amount of food supply. If it is 

 considered that the size and yield of the mother plant have an 

 influence upon the size and yield of the daughter plants, then we 

 must consider that this influence is decidedly less than the influence 

 exerted by the size of the seed. If the size and yield of the mother 

 plant have no effect upon the offspring, then the yields from diffe- 

 rent weights of seed might be expected to be somewhat in Pro- 

 portion to the weights of seed. Moore. 



Waldron, L. R., Heredity in populations and in pure lines. 

 (Plant World. XIII. p. 1-12. flg. 1—5. 1910.) 



This paper is a summary of Johannsen's work on "pure lines" 

 published in 1903. Johannsen first showed that in the case of the 

 weight of beans Galton's law of regressions would hold for the 

 Population taken as a whole. Then, treating the same material by 

 the method of pure lines as a means of analysis, he w^as able to 

 show^ that in any pure line the regression disappears and the off- 

 spring corae true to the peculiarities of their parents. This new 

 method of approach has already had an important influence on 

 subsequent work in variabilit}^ Gates. 



Livingston, B. E., ihe Porous Cup Atmometer as an Instru- 

 ment for ecological research. (Rep. Brit. Ass. Sei. Winnipeg, 

 Sect. K. p. 671—672. 1909.) 



Evaporation is determined primarily by temperature, humidity 

 and wind velocity, and is usually deeply affected by variations in 

 rainfall and sunshine, therefore an apparatus for measuring evapo- 

 ration will sum the various meteorological elements as they influence 

 the plant. The Instrument consists of a cup of porous clay so mounted 

 that evaporation may be recorded; the details are given in another 

 paper (Publication 50, Carnegie Institution). The advantages of this 

 cup over an open dish of water are discussed in some detail, also 

 the coefficient of correction necessary for each cup used. 



W. G. Smith. 



Mae Dougal, D. T., The making of parasites. (Plant World> 

 XIII. p. 207-214. Sept. 1910.) 



The fact that nearly one-half of the seed plants are either para- 

 sitic or enter into partnership with fungi of the soll and that this 

 tendency leads towards atroph}'^ of the vegetative organs and the 

 development of specializations of structure and habit seen in asso- 

 ciations and dependent nutrition has a tremendous significance for 

 students of evolution. After a discussion of mechanical adhesions 

 and the ways in which these may be brought about, the general 

 results of a number of experiments in the succulents growing in the 

 vicinity of the Desert Laboratory at Tucson, Ariz., are given. 

 These results showed that only plants possessing a sap having a 

 higher osmotic activit}^ than the plant upon which they are growing 

 can become parasitic. Attention is called to the fact that raany 

 plants may automatically increase the osmotic activity of the sap 



