AGRICULTUEAL BOTANY. 129 



current are said to have shown that potassium may be made to pass for a con- 

 siderable distance into vegetable tissues. 



The function of manganese in plants, W. P. Kklley {Bot. Ga~., 57 (191Jf), 

 No. 3, PI). 213-227). — This is a shorter account of work already noted (E. S. R., 

 27, p. 129). 



The mechanism of oxidation and reduction in vegetable tissues, J. Wolff 

 iCoiupt. Rend. Acad. 8ci. IParis], 158 U'J14), No. 16, pp. 1125-1127).— Bescrih- 

 ing experiments producing oxidation and reduction in tissues and juices of 

 apple and pear and in solutions, and referring in this connection to the claim 

 of Lindet (E. S. R., 6, p. 775) that brown coloration in juices or in bruised 

 tissues of pome fruits is due to the presence of a diastase, also to that of 

 Bourquelot and Fichtenholz (E. S. R., 24, p. 31) that arbutin was demonstrated 

 in pear leaves, the author claims that the i)henomena here described show a 

 causal relation to the same general sort of mechanism demonstrated in those 

 experiments. 



The influence of vertical illumination upon growth of the coleoptile of 

 Avena sativa, E. Vogt (Bcr. Dciit. Bot. Gcscll., 32 (1914), No. 3, pp. 173-179, 

 fig. 1). — The author gives some results of tests made by himself on the influence 

 of vertical illumination of the coleoptile of A. sativa. Graphically represented 

 data show little change during exposure, but a subsequent slight check in 

 elongation of this part for 12 minutes, then a steep rise for about IS minutes, 

 followed by a somewhat less steep decline for about 45 minutes, with two 

 decreasing interruptions, to the original rate of growth. 



The investigations here sketched tend to show that artificial vertically inci- 

 dent light of not too high intensity or too long duration exerts a predominantly 

 favorable influence upon the rate of elongation of A. sativa, while shading 

 tends to check the growth in plants accustomed to light; also that sudden and 

 considerable change in illumination acts as a stimulant, to which this portion 

 of the plant reacts in somewhat rhythmical alterations of growth rate. 



Study of rest period in potato tubers, C. O. Appleman {Maryland Sta. Bui. 

 1S3 {1914), pp. lSl-226, figs. 18). — The author has given the results of a bio- 

 chemical and physiological study of the rest period in tubers of Solannm 

 tuberosum. 



It was found that under normal planting conditions potato tubers will not 

 sprout for several weeks after harvest. During this rest period certain changes 

 occur which are essential to the growth processes. These changes are spoken 

 of as after-ripening. The carbohydrate transformation during the rest period 

 was found -to be entirely dependent upon changes in temperature. Active 

 diastase and invertase were found present at all stages of the rest period, but 

 showed no increase under normal growing conditions until the tubers began 

 to sprout. The oxidation of pyrogallol was more active when juices from tubers 

 at the end of the rest period were used than with those from immature tubers. 

 After-ripening, it is claimed, does not involve protein hydrolysis. Protein, 

 lipoid, organic extractive, and inorganic phosphorus, calculated to percentage 

 of total phosphorus, remained constant up to the time of sprouting. The 

 metabolic changes involving these foi'uis of nitrogen and phosphorus began 

 rather suddenly and were concurrent with sprouting, and the same was true 

 with regard to diastase. 



Suberization reduces permeability of the skin to water and gases. It was 

 found that potatoes may be sprouted at any time during the rest period by 

 removing the skin and supplying the tubers with favorable growing condi- 

 tions. The earliest sprouting occurred when the skins of the tubers had been 

 removed and the potatoes cut transversely. 



