AGRICULTURAL BOTANY. 129 



ties of these beans are quite extensively imported into England and other parts 

 of Europe for feeding stock as well as for human food. 



An examination of these beans showed that many contained prussic acid in 

 injurious amounts. It has been stated that by cooking them the glucosid is 

 removed, but there appear to be indications that this is not always the case. In 

 view of the interests concei'ned, the authors think it desirable that an extended 

 investigation be carried on to determine their suitability for use as a feeding 

 material, particularly as many of the white varieties may come into use as a 

 human food, since they closely resemble the small haricot beans in appeax'ance. 



A quantitative study of transpiration, Grace L. Clapp {Bot. Oaz., Jf5 {1908), 

 No. J/, pp. 25.!f~267, figs. 2, graphs 30). — A series of studies has been carried on to 

 determine which of the plants available to American teachers are best adapted 

 for the demonstration or investigation of the different physiological processes, 

 and the present paper gives the results of the investigation on the transpiration 

 of 30 species of plants. In this investigation the author determined the actual 

 amount of water lost by the plants growing under ordinary conditions in green- 

 houses, and at the same time determined the transpiration under various 

 conditions which admit of control and repetition. 



The first choice in respect to excellence of material for study falls on Chrys- 

 (tnthemum frutescens, Tropceolum jnajus, Pelargonium domesticum, Fuschia 

 speciosa, Senecio petasitis, S. mikanioides, Pelargonium zonale, Heliotropium 

 peniviaiiitm, and Pelargonium peltatum. These were found best since they lose 

 large amounts of water, are easily obtainable at any time of the year, and may 

 be readily grown in houses oi" in the greenhouse. 



In the course of the study it was brought out that there are 2 daily extremes, 

 a maximum about midday, when the sunlight is most intense, heat usually the 

 greatest, and moisture in the atmosphere the least, but with a good supply of 

 water in the soil. The minimum occurs some time during the night, when the 

 temperature is low, the atmospheric moisture approaches saturation, the dark- 

 ness is complete, and in most plants the stomata are closed. 



It was further found that in general the transi)iration of ordinary plants 

 grown in greenhouses amounts to about 50 gm. per hour per square meter of 

 surface for the daytime and 10 gm. at night. 



The relation between the size of the stomata and photosynthesis in grasses, 

 V. KoLKUNOV (Zhur. Opuitn. Agron. (Russ. Jour. Expt. Landw.), 8 {1901), No. 4, 

 pp. 369-381). — In investigations previously noted (E. S. R., 19, p. 225) the author 

 showed that the lowering of evaporation by cultivated plants is brought about 

 by a reduction in the size of the stomata. As a measure of such lowering the 

 author finds it convenient in grasses to consider the length of the stomata. 



In connection with these investigations a study was made on the relation of 

 photosynthesis to the size of the stoqiatic orifices. Experiments were carried 

 on in which leaves of grasses were placed in tubes containing gas of a known 

 carbon dioxid content, then kept for li to 2 hours in the light and the remain- 

 ing carbon dioxid determined. Experiments were carried on in this way 

 with different varieties of wheat, barley, millet, and other grasses, and in 

 each case the size of the stomata as well as the amount of carbon dioxid 

 assimilated was noted. 



The author was led to the general conclusion that the assimilation in grasses 

 varies in proportion to the size of the stomatic orifices. 



Incidental to this investigation it was found that the assimilation of differ- 

 ent species was differently affected by like intensities of light. In one instance, 

 on a dark rainy day the leaves of millet did not decompose any carbon dioxid, 

 while the leaves of a variety of Turkestan wheat decomposed it as energetically 

 as on bright sunny days. 



