I260 AGRICULTURAL BOTANY, CHEMISTRY AND PHYSIOLOGY OF PLANTS 



grains. Equal percentages of nitrogen content correspond to equal percent- 

 ages of glass}- grains. Thus, according to the exj)erinients in 1915, with 

 sodium sulphate, sodium nitrate and ammonium nitrate, for the first two 

 salts, at 32-38 % of glassiness of the grains, the content of nitrogen is nearly 

 the same, fluctuating about the figure of 2 % (2.40-1.969 %). When the 

 glassiness reached 100 %, an almost uniform percentage of nitrogen is ob- 

 tained with all the salts, near 2.8 % (2.711-2.907 %). 



The fact emphasised by the Author in his diagrams should be noted, 

 that in the grain, even when the whole of it has become vitreous, the con- 

 tent of nitrogen continues to grow with the increase of the osmotic pressure 

 according to the rule formulated herewith. 



It is therefore concluded that the glassiness of the grain is not the factor 

 on which the total content of nitrogen of the wheat grain depends, but that 

 this latter property, as likewise the glassiness, depends, under certain ex- 

 ternal conditions of growth, on a more general cause, namely the osmotic 

 pressure of the soil moisture and the quantity of soluble nitrogen contained 

 in the soil. For instance, it may be assumed that the increase in the osmotic 

 pressure causing a rise in the nitrogen contained in the grain of " Bielotourka " 

 wheat, also produces an increased degree of glassiness of the grain. The 

 influence of the degree of moisture of the soil may be explained by the 

 fact that a greater humidity of the soil means a weaker concentration of 

 the solutions and a lower osmotic pressure of the soil solution. 



965 - Senile Changes in the Leaves of Vitis vulpina L., and certain other Plants. 



— Yi-Eti-EDiCT llh'RV.isM., in Cornell University, AgriciiUural Experiment Station of the 

 College of Agriculture, Memorandum No. 7, pp. 275-370, tables 59 -f 52-58 fig. Ithaca, 

 New York, June 1915. 



An examination of the observations of modifications resulting from se- 

 nility in perennial plants indicates that in this direction no investigations 

 have been carried out on the lines of those undertaken in the animal king- 

 dom. Observations on the effects of age in plants represent occasional re- 

 cords rather than investigations. The reason of this appears to be the ta- 

 citly accepted belief that since new leaves, stalks and roots are constantly 

 formed from persistent embryonic cells, senility, as it occurs in animals, 

 must not be considered in relation to plants, and that this term, when used 

 of plants, merely means that the conditions have become so unfavoitrable 

 that parts in process of growth are killed. This view was encouraged by 

 the very advanced age attained by some trees. The importance, however, 

 of determining whether or not senile modifications occur in plants, lies not 

 only in the scientific interest of this determination but also in its reaction on 

 the vexed question relating to the effects of the continuous vegetative pro- 

 pagation of seed-producing plants. 



For his investigations the writer adopted Vitis vulpina L,-, a plant re- 

 markable for the extreme vigour with which it puts forth a new growth every 

 year, in order to reduce to the lowest possible mininunii the likelihood of 

 imfavourable conditions other than old age. He therefore carefully sought 

 out, in the vicinity of Ithaca, New York, and Cincinnati, Ohio, vines of 

 different ages growing near to each other under the most similar possible ex- 



