AGRICULTURAL BOTANY. 325 



The chemical nature of root secretions, J. Stoklasa and A. Ernest iJalirb. 

 Wiss. Bot. [Pruigsheini], J,6 {1908), No. 1, pp. 55-102, pis. 5).— Reviewing at 

 some lengtli the investigations on this subject, and summarizing their own 

 experiments, the authors arrive at the general conclusion that the most im- 

 portant if not the only active agent excreted by roots is carbon dioxid, but that 

 both carbon dioxid and organic acids are produced by soil bacteria in consider- 

 able amounts. 



The structure of root tubercles in leguminous and other plants, W. B. 

 BoTTOMLEY (Rpt. Brit. Assoc. Adv. 8ci., 1007, p. 693). — According to the author, 

 the root tubercles of all leguminous plants examined appear to arise endoge- 

 nously from the cortical cells just outside of the endodermis of the roots. These 

 cells are stimulated by the infection thread, which grows almost straight from 

 the infected root hair toward the vascular cylinder of the roots, and a conical 

 mass of cells develops which forms the young tubercle. In fully developed 

 tubercles the bacteroid tissues nre situated entirely within the vascular strands. 



The root tubercles of alder, Elieagnus, and Cycas are to be morphologically 

 considered as lateral roots, showing a central vascular cylinder and well-marked 

 endodermis, completely surrounded by bacteroid tissues. These tubercles 

 branch dichotomously and are perennial, thus differing from leguminous tuber- 

 cles, w^hich are of limited growth. 



The assimilation of free atmospheric nitrogen through the fungus of 

 Lolium temulentum, E. Hannig (Bci: Deut. Bot. Gesell., 26a (1908), No. 3, 

 pp. 23S-2Ji6, fig. 1). — By means of cultures of L. temulentum, in which fungus- 

 infested seed and seed free from the fungus were used, the author has under- 

 taken to determine the possibility of the assimilation of atmospheric nitrogen 

 by this plant in symbiosis with the fungus. 



It was found that the seed containing the fungus were considerably richer in 

 nitrogen than those not so infested, but in the cultures comparatively little dif- 

 ference was shown in the growth of the plants from the different lots of seed. 

 As a result of the analyses the author confirms the observation of Hiltner 

 (E. S. R., 11, p. 1016) that there is a slight assimilation of atmospheric nitro- 

 gen by infested L. temulentum. 



Heredity in plants and animals, T. B. AVood and R. C. Punnett (Trans. 

 Highland Agr. Soc. Scot., 5. .sci:, 20 (1908), pp. 36-86, figs. //).— This is a dis- 

 cussion of ilendel's principles and their bearing on agricultural problems, the 

 data discussed being drawn from in\estigations of Mendel, Hurst, Johannsen, 

 De Vries, Bateson, Biffeu, and others. 



A critical review of the known cases of bud variation, P. J. S. Cramer 

 iXatuurk. Verhandel. Holland. Maatscli. Wetensch. Haarlem, 3. ser., 6 (1907), 

 Xo. 3, pp. XVin+.i74)- — After a general review of the subject of variation, the 

 author takes up and critically discusses a large number of bud variations and 

 attempts to classify them according to their most striking characters. 



Suggestions concerning certain bud variations, E. M. East (Plant World, 

 11 (1908), \o. 4, pp. 77-83). — The author gives an analysis of a number of bud 

 variations of potatoes, tomatoes, and other plants, most of the variations being 

 changes of color. In the majority of cases he holds that bud variation is simply 

 a loss of a dominant character, and hence the appearance of a related recessive 

 character. This he claims will explain fully 75 per cent of the recorded bud 

 variations, and it is believed that an increasing knowledge of Mendelism will 

 extend the proportion of cases to which it is applicable. 



Variation in peas, F. A. Waugh and C. S. Pomeroy (Massachusetts Sta. Rpt. 

 1907, pp. 65-70, dgms. 3). — For several years past the horticultural division of 

 the station has been carrying on investigations with peas to study the so-called 



