AGRICULTURAL BOTANY. 523 



p. 633), the authors srive an account of investigations to determine tlie progress 

 of carbohydrate transformation as influenced by different temperatures, etc. 

 The sweet potatoes were studied during a period of 10 or 12 days, immediately 

 after they had been dug, at 30, 15.5, and 5° C, and a second lot, which had 

 been in storage during the first 12 days, was investigated for another period 

 of equal length after the expiration of the first. 



From the data obtained, it appears that in the carbohydrate transformation 

 in stored sweet potatoes, starch is first converted to reducing sugar and cane 

 sugar is synthesized from the reducing sugar. The rates of starch hydrolysis 

 and of sugar synthesized in a general way conform to the Van't Hoff tempera- 

 ture rule for rates of chemical reactions. At high temperatures the reactions 

 are rapid at first, but soon become slower and approach an end point. At low 

 temperatures the rates are slower and the end point is so shifted as to permit a 

 greater concentration of sugar. The reactions are said to be continuous. 



In the growing sweet potato the concentration of sugar remains comparatively 

 low, the extensive conversion of starch into sugar apparently being inhibited 

 by the activity of the vines. When the vines are destroyed and the flow of 

 materials to the roots is interrupted, the carbohydrate transformations charac- 

 teristic of stored sweet potatoes are begun, even if the roots are left in the 

 ground. 



Respiration in hig'her plants, F. W. Neger {Natiirwissenschaften, 3 {1915), 

 Nos. 19, pp. 2SS-2Jt2, figs. 2; 20, pp. 249-253, figs. S). — Discussing previous obser- 

 vations regarding the behavior of stomala in relation to gas exchanges, the 

 author states that in case of a fir twig exposed to sulphur dioxid gas after a 

 portion had been partly isolated by bending at a certain point, the foliage of the 

 portion beyond this point was retained in a green state, while that of the other 

 portions became discolored and dropped off, as is common in case of smoke 

 injury. The leaves of the portion beyond the injury were found to have closed 

 their stomata, apparently on account of the partial drying of the leaves. 



Experiments with Euonymus japonica showed that infiltration occurs more 

 readily in leaves injured by the presence of sulphuric acid evaporating from 

 an aqueous solution thereof than in case of normal foliage. Plants seem unable 

 to protect themselves against noxious gases in the air, the stomata apparently 

 forming the chief means of access to the susceptible tissues of the leaves. 



Other factors claimed to be more or less influential in stomatal behavior are 

 discussed, such as illumination, temperature, moisture, age of leaves, daily and 

 seasonal periodicity, transpiration, and altitude. 



Two types of leaves are distinguished as significant in this connection, namely, 

 homobaric, in which there is free communication between all the intercellular 

 spaces, and heterobaric, in which sharply defined areas are hermetically sealed 

 apart. The former class corresponds somewhat roughly to the evergreens, the 

 latter to deciduous plants. 



Relation of catalase and oxidases to respiration in plants, C. O. Apple- 

 man (Mari/Jand Sta. Did. 191 (1915), pp. 16, figs. 2; nhs. in Jour. Wash. Acad. 

 Sci., 6 {1916), No. Jf, p. 101). — After a review of some of the more important 

 literature relating to catalase activity in connection with respiration, the author 

 gives an account of experiments carried out with potatoes in which he under- 

 took to determine the relation of catalase and oxidase activity in the potato 

 juice and the intensity of respiration in the tubers under different conditions. 



The rate of transpiration was found to be influenced by various treatments, 

 and it also varied in different parts of the same tuber and in tubers of different 

 varieties. The data obtained are considered by the author to indicate that 

 the oxidase content of potato juice gives no indication of the intensity of re.spi- 



