1018] AGRICULTURAL BOTANY. 223 



deciduous habit and to be closely related to the ability of certain species of 

 cacti to endure the Michigan winters. 



Does the movement of air affect the growth of plants? Alma Hollinger 

 (Rpt. Mich. Acad. Sci., 17 (1915), pp. 159, 160). — In a preliminary report on 

 investigations not yet completed, the author states that in darkness the move- 

 ment of air apparently does affect favorably the rate, duration, and vigor of 

 growth ; also that it affects coloration, leaf spread, etc., in the several plants 

 tested. 



A method of controlling' the rate of air movement in transpiration experi- 

 ments, V. H. Dlackman and R. C. Knight {Ann. Bot. [London], 31 (1917), 

 No. 122, pp. 217-220, fig. 1). — The authors, considering it advisable that trans- 

 piration and evaporation experiments with plants be carried on under condi- 

 tions of constant air movements regulable at will, have devised an air-flue ap- 

 paratus which is described as convenient, reliable, and satisfactory for air 

 movement up to about 25 meters per minute. 



The interrelations of stoniatal aperture, leaf w^ater content, and transpi- 

 ration rate, R. C. Knight (Ann. Bot. [London], 31 {1917), No. 122, pp. 221-2^0, 

 figs. 4)- — Employing the air-flue apparatus above described in tests with 

 various plants (of which Eupatorium adenophorum was found to be the most 

 useful for this purpose) under controlled conditions, the author claims to have 

 found that in many cases there is no necessary agreement (often, in fact, an 

 inverse relation) between stomatal opening and transpiration rate. Water con- 

 tent of the leaf shows a close and direct relation to transpiration rate. Stomatal 

 aperture is not reduced by slight water deficiency in the leaf, so that stomatal 

 response to incipient dryin.? niay be excluded as a chief factor in the mainte- 

 nance of water content. Stomata are, however, very sensitive to the changes in 

 illumination, and with increasing light intensity continued opening of the stomata 

 may coincide with continued decrease of water content. 



On the reduction of transpiration observations, N. Thomas and A. Febgtj- 

 SON {Ann. Bot. [London], 31 {1917), No. 122, pp. 2^1-255, fig. i ) .—Experiments 

 described are claimed to show that the evaporation from a circular water sur- 

 face is not proportional to the area of the surface if that surface be within 2 

 or 3 cm. of the top, nor is it proportional to the linear dimensions of a surface. 

 It is stated to be. for full circular containers, approximately proportional to the 

 cube of the square root of the radius. Errors amounting to as much as 40 per 

 cent are claimed to arise in determining the water surface equivalent to a given 

 atmonieter. 



Methods of calibration are described which are claimed to obviate such errors. 



Oxidation and reduction in vegetable tissues. — I, The mechanism of the 

 reaction, J. Wolff {Ann. Inst. Pasteur, 31 {1917), No. 2, pp. 92-95). — Three 

 phases of the more mechanical part of this work are presented and briefly dis- 

 cussed in this article as preparatory to the report given below. 



Oxidation and reduction in vegetable tissues. — II, The presence in a large 

 number of plants of a diphenol presenting important analogies with pyro- 

 catechin, J. Wolff and Nadia Rouchelman {Ann. Inst. Pasteur, SI {1917), No. 

 2, pp. 96-105). — Discussing briefly the method employed and tabulating the 

 results of observations made on a large number of plants, the authors conclude 

 that peroxid is not present in vegetable sap, the presence of an oxidase (lac- 

 case) being necessary to the production of a positive result. It is thought that 

 the reaction which has been believed to show the presence of nitrites and of 

 peroxids in plants, and the eventually injurious effects of the latter, are due in 

 the large majority of instances to the presence of a phenol, probably pyrocate- 

 chin. This is considered to play an important part in the processes of oxidation 

 and reduction that occur in plants. 



