426 EXPERIMENT STATION RECORD. IVol. 38 



perhaps a principal hindrance to growth. The relative coldness of the waters 

 from the ravine slopes may be an influence modifying that of soil moisture. 



The climax formation of western Pennsylvania is a mesophytic deciduous 

 forest of which Acer, Fagus, Castanea, and Quercus are the dominant members. 

 The composition of the climax formation is directly referable not to physio- 

 graphical but to climatic conditions. 



A list of Japanese fungi, M. Shikai and I. Miyake {Tokyo, 1017, 2. ed., pp. 

 735+7S). — This consists of an alphabetical list of species of fungi known to 

 occur in Japan. 



Self-sterility, C. W. Mooke {Jour. Heredity, S {1917), No. 5, pp. 203-207, figs. 

 3).— A study of Tradescantia. TrifoUum hybridum, Medicago sativa, and Papa- 

 ver rhwas, regarding their capacity for cross-fertilization as compared with 

 that for self-fertilization, showed differences in this respect in favor of the 

 former method which were notable in case of Tradescantia and somewhat less 

 so in Trifolium. These and other observations noted are thought to be capable 

 of interpretation either on the ground of an inhibitor in the pollen grain or 

 stigma which in some cases prevents a pollen grain from extending itself to the 

 stage of self-pollination, or else on that of an early deficiency of food supply for 

 the tube and its consequent stoppage of longitudinal growth short of the point 

 where self-fertilization is possible. The latter explanation is considered as the 

 more probable, the greater thickness of the pollen tubes in Tradescantia indi- 

 cating that the food supply is more favorable to the nourishment of a self-pollen 

 tube than it is to that of a cross-pollen tube. The tubes thus express their 

 growth chiefly in thickness and fail to carry the nucleus to the embryo sac. 



Artificial production of galls, M. Molliaku {Compt. Rend. Acad. Sci. [Paris], 

 165 {1917), No. Jf, pp. 160-162, fig. 1). — Larvaj of Avlax papavcris were crushed 

 in a small quantity of water which was then Altered under pressure and forced 

 into the pistil (some entering the ovary) of Papaver rliocas. This developed a 

 decided hypertrophy in certain of the placental lamella? resembling the effects 

 pi'oduced by the presence of the larvre themselves. Similar results were ob- 

 tained with P. sonmiferum, which is said not to be attacked by A. papaveris. 



The movement of chromatophores, C. Sauvageau {Compt. Rend. Acad. Sci. 

 [Paris], 165 {1917), No. Jf, pp. 158, 159, fig. 1). — Saccorhiza hvlhosa is said to 

 exhibit in a remarkaljle degree the tendency to contract its chromatophores 

 rapidly and considerably on exposure to strong diffused light, this change being 

 reversible in darkness. 



Physiology and biology of nitrogen-fixing bacteria, V. L. OfifELiANSKii 

 {Arch. Sci. Biol. [Petrograd], 19 {1915), No. 2, pp. 162-208, pi. 1; abs. in Intcr- 

 nat. Inst. Agr. [Rome], Internal. Rev. Sci. and Pract. Agr., 7 {1916), No. 7, pp. 

 9U, 945; Jour. Soc. Chcni. Indus., 36 {1917), No. 1, p. J,0).—'T\\e author has 

 endeavored to make a digest of the large amount of existing information on 

 the physiologj' and biology of AzotobaHvr chroococcum, supplementing this by 

 the results of his own researches. The subjects dealt with are the methods of 

 accumulation of Azotobacter in selected culture, methods of isolation, growth 

 in solid and liquid media, and influence of temperature and aeration. The 

 most attention is devoted to the fixation of free atmospheric nitrogen, and in 

 particular the conditions insuring the highest efliciency of the species under 

 study, with reference not only to the absolute quantity of nitrogen fixed but 

 also to the quantity of nonnitrogenous substances oxidized. 



Relations between nitrogen fixation and the consumption of nonnitrog- 

 enous organic substances by nitrogen-fixing bacteria, V. L. OmelIanskii 

 {Arch. Sci. Biol. [Petrograd], 18 {1915), No. 4, pp. 327-337, figs. 2; abs. in Inter- 

 nat. Inst. Agr. [Rome], Internat. Rev. Sci. and Pract. Agr., 7 {1916), No. 7, pp. 



