1916] AGRICULTURAL BOTANY. 821 



that the red coloration is a consequence of the changes leading to nonastringency 

 and is itself not the cause of that condition. 



A visual method for accurately measuring astringency is given. It is based 

 on the observation that the degree of astringency depends on the degree of 

 adsorption of tannin by the X-cellulose (a carbohydrate of the nature of 

 cellulose). 



The theories of photosynthesis in the light of some new facts, H. A. Spoehr 

 (Plant World, 19 {1916), No. 1, pp. i-i6).— Following a review of the studies 

 which have been concerned chiefly with the reduction of carbon dioxid to 

 formaldyhyde, the detection of formaldehyde in illuminated green plants, and 

 the experimental employment of formaldehyde as the sole source of carbon 

 for plants, the author gives an account of experiments carried out by himself 

 at Tucson, Ariz., where the days are largely clear and the light intense, a great 

 number of experiments having been made with the object of reducing carbon 

 dioxid by means of light from various sources. 



It was found that neither when mixed with water vapor nor when dissolved 

 in water did carbon dioxid, though exposed from 1 to 150 hours, ever yield 

 conclusive tests for the presence of formaldehyde. Formic acid was the only 

 reduction product obtained, which fact is considered as important. The author 

 states that his studies on the action of gaseous formic acid on green plants in 

 the light show that, although this compound is toxic to the roots, the chlorophyl- 

 lous portions develop normally in an atmosphere of formic acid, show an 

 appreciable gain in dry weight, and form starch. 



It is stated that, although the same criteria which have been applied to the 

 formaldehyde theory may be urged perhaps even more consistently in favor of 

 a formic acid hypothesis, this fact still does not appear to the author to justify 

 the formulation of a formic acid hypothesis. 



A simple and rapid method of studying respiration by the detection of ex- 

 ceedingly minute quantities of carbon dioxid, A. R. Haas (Science, n. ser., 

 44 (1916), No. 1125, pp. 105-108). — A description is given of a simple apparatus 

 that may be used in determining the respiration of organisms, the amount of 

 respiration being accurately observed by changes in the colors of indicators 

 added to solutions which contain the organisms. 



It is found that exceedingly small amounts of carbon dioxid may be deter- 

 mined with great accuracy. As changes in color often occur within a few 

 minutes, it is claimed that the experiments may be so shortened as to exclude 

 pathological changes in the organisms. As the amount of carbon dioxid can 

 be determined without disturbing the organisms, a study of the dynamics of 

 the method is made possible. 



The controlling influence of carbon dioxid. — III, The retarding effect of 

 carbon dioxid on respiration, F. Kidd (Proc. Roy. Soc. [London], Ser. B, 89 

 (1916), No. B 612, pp. 136-156, figs. 3).— Previous work (E. S. R., 32, p. 328) 

 has led to the conclusion, among others, that the resting condition of moist 

 seed often observable in nature is primarily a phase of autonarcosis under 

 the influence of carbon dioxid produced by the seed itself (retardation and 

 suspension of normal activity in plant protoplasm being produced by carbon 

 dioxid in conditions otherwise favorable to growth and during a stage nor- 

 mally characterized by vigorous growth). The author has now extended these 

 investigations to plant tissues in general in order to determine the mechanism 

 of such narcosis. The influence of carbon dioxid upon respiration has been 

 studied on account of its apparent connection with growth by cell division. 



It has been found that carbon dioxid in plant tissues causes a depression 

 of anaerobic carbon dioxid production. This depression is not due to perma- 

 nent disorganization, as it is temporary and disappears with the disappearance 



