820 EXPERIME^^T STATION EECOKD. [Vol.41 



reached by Teesdale in work previously noted (E. S. R., 31, p. 743), is said to 

 have shown that Lari.v laricina and L. occidentnlis, while similar in most 

 characters, are dissimilar In those structures most concerned in the passage 

 of creosote into the wood. The similarity is thought to be due to differences 

 in penetrable bordered pit areas. Additional data bearing uiwn work of Tees- 

 dale are given in the appendix: to the main report. 



Salt ratios in soil cultures, R. P. Hibbard (Ann. Rpt. Mich. Acad. Sci., 20 

 (1918), pp. IJfl-^lSO). — This is a brief account, with discussion of indications 

 and bearings, regarding the work which has been previously noted (E. S. R., 

 39, p. 419). 



[Mineral nutrient solution for maize], P. Maze (Ann. Inst. Pasteur, SS 

 (1919). Xo. 3, pp. 139-173, figs. S).— Work previously noted (E. S. R., 33, p. 

 522; 34, p. 525) has been followed up with studies on the nutritive require- 

 ments of maize. 



It is claimed that boron, aluminum, (luoriii, and iodin are indispensable to 

 the development of maize in the same sense as are nitrogen, phosphorus, potas- 

 sium, calcium, magnesium, sulphur, iron, chlorin, silicon, magnesium, and zinc, 

 this fact raising the number of known elemental constituents to 18, including 

 the more abundant ones carbon, hydrogen, and oxygen. It is thought that 

 data obtained in this part of the work may give useful suggestions looking 

 to more direct and practical work along these and closely related lines. The In- 

 fluence of organic matter, of aeration, and of the oxidation of iron are also 

 systematically reported. 



The utility of sodium in relation to growth is regarded as not j'et estab- 

 lished. It is thought that the facts here noted, with discussion, indicate the 

 jiossibility of placing the elements which enter into nuti-itive solutions in two 

 categories, one containing those elements which condition organization, the 

 other, those which tend to prevent intoxication due to the accumulation of 

 certain compounds formed during the stages of transformation into substances 

 destined to become nutritive. 



Plant ecology and its relation to agriculture, AV. G. Waterman (Trans. III. 

 Acad. Sci., 10 (1917), pp. 123-129). — This is a brief systematic discussion re- 

 garding the nature, content, and scope of general ecology, and of the special 

 ecology of structural groups ; also regarding the relation of ecology to agri- 

 culture, the nature of contributions to ecology with illustrations, and the 

 proper place of ecologj' in agricultural study. 



Dwarf shore floras, H. W. Clark (Trans. III. Acad. ScL, 10 (1917), pp. U5^ 

 159, pU. 4, flu^- 2). — A list is given, vpith notes, of the species making up the 

 dwarf flora as noted in October, 1914, along the shore of the Mississippi River 

 near the Fisheries Biological Station at Fairport, Iowa. 



The individual dwarfing of upland plants, although referred to shortness of 

 their growing season as the principal cause, is thought to offer a complex and 

 diversified problem assigi:iable to several other causes, among these inhibition of 

 root development by excess of soil moisture. 



Notes of the introduced flora of the Doug'las Lake reg'iou, H. A. Gleason 

 (Ann. Rpt. Mich. Acad. Set., 20 (1918), p. 153).— It is stated that within a few 

 miles of Douglas Lake, Mich., occur more than 100 species of introduced plants, 

 their local distribution showing that they are almost completely dependent 

 upon man for their dispersal and that they are unable to compete with the 

 native plants under natural conditions. The fluctuations in the number of 

 individuals from year to year .suggest a close relation to climatic conditions. 

 Areas occupied almost completely by introduced species soon develop into a 

 clo.sed association in which Poa pratensis is the dominant plant. 



