130 EXPERIMENT STATION RECORD. 



AGRICULTURAL BOTANY. 



Department of botanical research, D. T. MacDougal (Carnegie Inst. Wash- 

 ington Year Book, 8 (1909), pp. 57-70, pis. 2). — In addition to the report of 

 the director, in which the routine work of the laboratory at Tucson, Ariz., and 

 the branch laboratory at Carmel, Cal., is described, accounts are given of some 

 of the investigations now being pursued by the staff. These include studies 

 on the alterations in heredity induced by ovarial treatment, the water-balance 

 in succulents, origin of parasitism, growth and alterations in form and volume 

 of succulents, relation of evaporating capacity of the air to plant distribution, 

 activities of plants in tropical rain forests, distribution and movements of 

 desert plants, evaporation and other climatic factors in relation to distribution 

 of plants, physics of transpiration in plants, soil moisture in relation to plant 

 growth, root habits of desert plants, parasitism in desert plants, and inheritance 

 of structural characters in hybrids. 



Some evaporation experim.ents in relation to excessive transpiration, K. M. 

 WiEGAND (Abs. in Seience, n. ser., 31 (1910), No. 794, P- 43 Jf). — In order to 

 determine, if possible, the comparative value to the plant of hairy and cuti- 

 nized coverings, the author conducted a series of evaporation experiments in 

 which cotton or wax was spread over an evaporation surface of saturated 

 blotting paper, the covering being supposed to represent a hairy or a cutinized 

 leaf. 



Comparative readings of the loss of water from the variously treated blot- 

 ting papers in still air and in wind were made, and it was found that evapora- 

 tion was retarded much more by the wax than by the hair. The efficiency of 

 the hairy covering was much greater in wind than in still air, and even very 

 thin hairy coverings produced a noticeable retarding effect on wind. In sun- 

 shine the retarding effect was also marked. From this it is concluded that 

 plants probably make use of waxy coverings when transpiration is to be re- 

 tarded at all times, and hairy coverings when it is to be retarded only on 

 exi»osure to strong dry winds and sunshine. 



The effect of longitudinal compression upon the production of mechanical 

 tissue in stems, L. H. Pennington (Rpt. Mich. Acad. Sci., 11 (1909), p. 36)^ — 

 The effect of longitudinal compression on woody and herbaceous plants was 

 studied, the material consisting of sprouts and seedlings of locust, aspen, 

 sumac, sunflower, castor bean, and horse bean. In no case did the average of 

 a series of experimental plants show a gain in strength or in mechanical tissue 

 over a like series of control plants. 



The response of the g'uayule, Parthenium argentatum, to irrigation, F. E. 

 Lloyd (Abs. in Science, n. ser., 31 (1910), No. 794, pp. 434, 435). — A summary is 

 given of the results of a study of the guayule under irrigation in Mexico for a 

 period of two years. 



At the close of two seasons' growth, the irrigated plants showed only minute 

 quantities of rubber, although the growth of the plants was 8 times as great 

 under irrigation as under the ordinary conditions. The plants examined the 

 following April showed a large though not a maximum amount of rubber, and 

 the amount was found to increase as the water of irrigation was withheld. The 

 conclusion is reached that though the rate of secretion is slower in more rapidly 

 grown plants, it may after a di'ought approach the maximum. It is believed, in 

 view of the total amount of growth, that the total secretion of an irrigated plant 

 is greater in the long run than that of a field plant. 



Hail injury on forest trees, F. J. Phillips (Trans. Acad. Sci. St. Louis, 19 

 (1910), No. 3, pp. 49-56, pis. 7, fig. 1). — A report is given of a study of the injury 

 caused by a hailstorm at Hutchinson, Kans., in May, 1908. The effect on a 



