AGEICULTUKAL BOTANY. 221 



The withering of the leaves is believed to be caused more by the action of the 

 deleterious substances introduced into them from dead cells than from lack 

 of water, and the leaves of rooted plants j^rowai in nutrient solutions containing 

 sterilized decoctions of the same plant droop in from three to five days, and 

 become dry in from seven to eight days. 



In experiments in which portions of the stems were killed with picric acid, 

 alcohol, or copper sulphate, sufficient water was found to asceud through the 

 poisoned portions to continue the transpiration for a comparatively long period 

 and to allow the development of new branches. Picric and chromic acids and 

 corrosive sublimate greatly accelerated the amount of water evaporated in 

 poisoned plants. 



A bibliography of literature cited is given. 



The temperature coefficient of the duration of life of barley grains, T. H. 

 GooDSPEED {Bot. Gaz., 51 {1911), No. 3, pp. 220-22^) .—The temperature co- 

 efficient for the duration of the life of barley grains was determined by sub- 

 jecting different lots- of seed to temperatures varying from 55° to 70° C, after 

 which the vitality of the seed was tested. The time in minutes required for a 

 given temperature to act in order to inhibit subsequent growth was taken as 

 the duration of life under the conditions of the exi)eriment. 



At a temperature of 55° from 65 to 70 minutes' exposure was required to 

 destroy the germinative ability of barley seed, while at 70° an exposure of 

 from li to 2 minutes destroyed it. The average temperature coefficient for 

 every degree centimeter was 1.27, or about 11 for a temperature interval of 10°. 



The role of chlorophyll and light in the transformation of the carbon 

 dioxid and aqueous vapor of the air, A, Dunosc (Rev. G&n. Chim., 13 (1910), 

 Nos. 15, pp. 268-270; 17, pp. 273-281; 18, pp. 295-303; 19, pp. 316-320; 21, pp. 

 331-335). — A resume is given of various opinions regarding the functions of 

 chlorophyll and light in decomposing and transforming the carbon dioxid and 

 aqueous vapor of the air, the author supplementing the published results of 

 others by comments and observations of bis own. 



The respiratory energy of plants cultivated in different degrees of light, 

 E. Rose (Rev. Gdn. Bot., 22 (1910), No. 262, pp. 385-398, pi. 1).—A study was 

 made of the respiratoiy energy under different degrees of illumination of peas, 

 representing plants accustomed to strong light, and of Tcucrium scorodonia, a 

 shade plant. The intensity of the respiration was found to vary with the 

 different plants, with different degrees of illumination, and with different 

 stages of growth for the same plant. 



The portion of the spectrum influencing photosynthesis, P. A. Dangeard 

 (Compt. Rend. Acad. Sci. [Paris], 152 (1911), No. 5, pp. 277-279) .—Bj means 

 of a Nernst lamp, which was used day and night for a period of two months, the 

 author has studied the effect of different portions of the spectrum on the photo- 

 synthesis of an alga, ChloreUa sp. 



At the end of about eight days there was a distinct band of green growth, 

 which occupied the principal absorption band of chlorophyll, and this corre- 

 sponded to absorption band I of chlorophyll, which has a wave length of from 

 670, to 635, according to Jost. The spectrum of growth of the alga extended 

 from the limits of the infra-red nearly to line H in the violet, all the rays 

 occurring within these limits having a part in photosynthesis. Beyond this 

 there was little activity except in the region of absorption bands II and III 

 of chlorophyll. 



Leaf decay and autumn tints, P. Q. Keegan (Chem. Neivs, 102 (1910), No. 

 2657, pp. 213, 21If). — In a previous communication the author called attention 

 to the relation between the ash of leaves and their autumn tints. Subsequent 

 study has shown a connection between the vitality of the leaves and their 



