630 EXPEEIMEXT STATIOI^T RECORD. 



AGSICULTURAL BOTANY. 



A comparison of the alterations in the velocity of growth of certain seed- 

 lings through the action of rapid and slow electrons of the /3-rays of radium, 

 also a comparison of the role of chemical make-up and of physical factors 

 in determining these alterations, E. D. Congdon {Arch. Entivickl. Mcch. 

 Organ., 3// (1912), j)t. 2, pi). 267-280, figs. 2).— A study was made of the growth- 

 retarding effects upon small seeds of the rapid and slow electrons of *he 

 ^-radiations and also of the relative importance of physical factors and of 

 chemical composition in determining the sensitiveness of seeds to exposures to 

 radium. Five kinds of seeds were used, viz, blacls mustard, millet,- poppy, 

 Xicotiana, and Amarantus. 



It was found that by changing the penetrating power of the electrons their 

 effect was greatly modified. The embryos of mustard and millet were chiefly 

 affected, from which it is inferred that the embryo appeared more sensitive 

 than the stored foodstuff. It is thought probable that in the embryo there was 

 some injury of ferments or some unfavorable change of the general conditions of 

 solution rather than the breaking down of certain compounds which retarded 

 the growth. 



The slower electrons of the ^-radiations were found to have a greater retard- 

 ing action than the more rapid ones in proportion to their ionizing power, and 

 in proportion to their energy content on the small seeds used in the experiments 

 except when the embryo was protected by being turned away from the radium. 

 The retardative effect relative to the duration of exposure increased with the 

 lengthening of the exposure, then decreased, and finally became constant with 

 a slow increase of retardation. Very short irradiation in the case of mustard 

 and millet seed left doubt as to whether acceleration occurred or not. By 

 comparing the retardation of mustard and millet when the embryo was turneti 

 toward and away from the radium it was found that this part of the seed was 

 especially sensitive to the electrons. 



Dry matter, nitrogen, and mineral content of trees during the vegetative 

 period, E. Ramann and H. Bauee {JaJiri. Wiss. Bot. [Pringsheim'\, 50 (1911), 

 No. 1, pp. 67-83; abs. in Boi. Ccntbl., 119 {1912), No. 20, pp. IfOl, // .92). —Investi- 

 gations with young trees of various common species led to the following 

 conclusions : 



The new growth of foliage trees in the spring takes place chiefly by the 

 expenditure of materials previously stored, which are often broken down and 

 utilized in lar.se quantities in such trees. Conifers utilize in addition newly 

 assimilated materials, different species drawing on the soil supply during 

 different periods. For example, nitrogen assimilation by fir trees takes place 

 most actively during the period from September until about May 15 : by pine 

 trees from that time until July 15 : and by Scotch fir and larch trees thereafter 

 until September 15. The relations of the phosphorus compounds are about the 

 same. These facts suggest the cultivation of a mixed stand for the best utiliza- 

 tion of the abundant materials in a rich soil. See also previous notes (E. S. R., 

 25, p. 27; 27. p. 229). 



The mineral content of tree foliage as affected by day and night, 

 E. Ramann {.Jalirlj. MViss. Bot. [Pringsheimi, 50 {1911), No. 1, pp. 8',-91 ; al)s. 

 in Bot. Centhl., 119 {1912). No. 20, p. J/Ol). — Analyses made, in pursuance of 

 previous studies (see above), of leaves of beech, oak, hazel, plane tree, maple, 

 etc., indicate that while other minerals do not show any considei'able difference 

 for day and night, the calcium content (as computed on the basis of the dry 

 substance) increases at night and decreases by day. A possible connection is 

 suggested between the relative quantity of this mineral present and tlie trans- 



