May IS, 191S 



Hydrocya7iic-Acid Content of Sorghum 



183 



shown graphically. Here, again, there appears only a slight difference 

 in the hydrocyanic-acid content due to the added nitrogen fertilizer; but 

 contrary to the effect shown in Table I and the curve for plot W, the 

 slightly lower percentage of prussic acid was found in the plants from 

 the fertilized row. In plot 35 the decrease is insignificant, and in plot 30 

 the two curves cross each other twice. Taking into consideration the 

 results from all three plots, it appears that on soils deficient in nitrogen 

 added nitrogen will slightly increase the prussic acid in sorghum; but 

 that with a plentiful supply of nutrients in the soil added nitrogen does 

 not affect the amount of the acid in the plants. 



A plentiful supply of nitrogen in the soil will permit the maintenance 

 of a definite amount of prussic acid at a given stage of growth ; but it may 

 be that this amount is not absolutely required and that if the supply of 



Fig. 2. — Curve 



showing the distribution of hydrocyanic acid in sorghum. The percentage of hydro- 

 cyanic acid is based on dry matter. 



nitrogen is deficient the plant maintains the equilibrium of other nitrog- 

 enous compounds at the expense of the prussic acid. 



Figure 2 shows the distribution of the prussic acid in the two varieties 

 of sorghum, and an interesting varietal difference appears. The stalks 

 of feterita contain in the early stages a relatively high percentage of 

 prussic acid, and the acid persists in small amount through most of the 

 life of the plant. The stalks of Orange sorgo, however, show less of the 

 acid in the beginning, and it disappears entirely by the fortieth day. 

 Both plots show an increase of the acid in the leaves during the early 

 stages, and later a decrease; the acid in the leaves had not completely 

 disappeared in this experiment by the ninety-second day. Evidently 

 the cyanogenetic glucosid is related to the vital processes of the plant, as 

 it occurs in the largest quantity in those parts of the plant which are 

 most active photosynthetically and during those stages when the plant 



