634 EXPERIMENT STATION RECORD. [Vol.41 



Root habit and plant distribution in the far North, H. E. Pulling (Plant 

 World, 21 (191S), No. 9, pp. 223-233, fig. i).— The author, classifying root sys- 

 tems, regards black spruce, tamarack, and canoe birch as being of rigid shallow 

 habit ; white spruce as of flexible shallow root habit ; balsam poplar as of deep, 

 flexible root habit; and jack pine and white pine as of deep, rigid root habit. 

 Other differences which are discussed are omitted from the classification as 

 having no apparent bearing on forest composition in the far Nortli. 



Acclimatization of plants originally of hot climates, G. Rostek {Agr. 

 Colon. Utaly], 12 (1918), No. 4, pp. 231-25-',, fig. i).— Using the term acclimati- 

 zation (as opposed to naturalization) of plants, as involving the multiform 

 agencies employed by man, the author gives an account of some adaptations 

 that have been accomplished. 



Ends and methods of acclimatization, D. Lanza {Agr. Colon. [/iaZi/], 13 

 {1919), No. 1, pp. 1-15). — This is largely a discussion of the contribution of 

 Roster, above noted. 



Climax formations, F, E. Clements {Carnegie Inst. Wash. Year Book, 11 

 {1918), pp. 29Jf, 295). — Much attention has been paid to climax formations and 

 their successlonal development, principally to the formations of widest extent, 

 such as grassland, sagebrush, mesquite, and chaparral. As a consequence of 

 work done in this connection, it has been possible to recognize and delimit the 

 various associations of the nine climaxes for the first time and to point out 

 their relationships to each other, as well as to the associations of adjacent 

 formations ; also to draw more definite distinctions between climax and suc- 

 cessional indicators and to apply this to practical problems in grazing and 

 forestry. 



Mutations in the jimson weed, A. F. Blakeslee and B. T. Aveby, jk. {Jour. 

 Heredity, 10 {1919), No. 3, pp. 111-120, figs, ii).— Continuing former studies 

 (B. S. R., 37, p. 831), the authors have obtained evidence indicating the presence 

 of another (third) pair of factors for the jimson weed {Datura stramonium) . 

 A possible fourth factor is under investigation. 



In addition to this a study has been made of a number of mutative variants 

 of greater or less distinctiveness which appear to be inherited in a manner not 

 conforming to the Mendelian plan. A few of the more marked types of these 

 are discussed herein. They seem to transmit their distinguishing chai'acters as 

 a complex, usually to a part only of their offspring, chiefly through the 

 female side. 



In one instance a mutation has arisen which seems to have established a 

 distinct race or new species, breeding true but seemingly unable to cross with 

 the parent species. 



(Enothera rubrinervis, a half mutant, H. de Vries {Bot. Oaz., 61 {1919), 

 No. 1, pp. i-26).— Reporting, with discussion of facts and bearings, a study 

 of GE. ruhrinervis, its origin and descendants, and some characters of the latter, 

 the author states that Q£. ruhrinervis is a half nuitant, produced by the copula- 

 tion of a mutated gamete with a normal velutina gamete of CE. lamarckiana. 

 In consequence of this origin it produces about one-fourth empty seeds, one-half 

 GE. ruhrinervis which will repeat the .splitting, and a mass mutation, amounting 

 to about one-fourth of a pure or double mutant, which ha» been named deserens 

 and which is constant from seed and has no empty grains as hereditary features. 

 CE. ruhrinervis is not known to mutate otherwise to any noticeable degree, from 

 which it is inferred that the internal constitution causing the mass mutation is 

 not in itself the cause for further mutability. 



Crosses of (E. rubrinervis with CE. lamarckiana give three types of hybrids, 

 about one-fourth of the seeds being empty. One constant type resembles CE. 



