May IS, 1916 



Hydrocyanic-acid Content of Sorghum 



271 



the South Dakota plots, on the other hand, had little or no cyanid in the 

 stalks and had the most rapid growth. The Kansas stalks were very 

 heavy and succulent; they had developed very rapidly; and they con- 

 tained no cyanid whatever. The significance of this is not clear. 



7. Daily variation. — In order to compare the glucosid content in 

 sorghum with Treub's findings (7, 8) that in Pangium edule there is a 

 daily variation in glucosid content with a maximum about midday, some 

 analyses were made at sunset and sunrise of succeeding days, with the 

 results given in Table III. 



Table III. — Variation in the glucosid content of sorghum at different parts of the day 



There seems to be no constant variation in sorghum between night and 

 day. This lends support to the view that dhurrin is not a food storage. 



Although other factors have important bearing on the growth and 

 health of plants, those discussed above are the most readily measured 

 and, hence, best used as bases for comparison between widely separated 

 stations. It is realized that determinations of soil moisture at various 

 times throughout the growing season would give a much more accurate 

 idea of the available moisture than precipitation measurements. As 

 regards soil, each plot was grown on soil which has produced good crops 

 in the past and was cultivated according to the customary methods for 

 sorghum at those stations. Since the 191 4 experiments showed that soil 

 is a minor factor in affecting the hydrocyanic-acid content of sorghum, 

 the ignoring of this factor in the above comparisons is justified. 



SUMMARY 



Two varieties of sorghum. Southern Cane and Early Amber, ^'\•ere 

 grown on plots in Minnesota, Utah, Kansas, and South Dakota under 

 widely different climatic and cultural conditions. The amount of the 

 glucosid dhurrin in each plot varied considerably. The following corre- 

 lations relative to the amount of glucosid were found to exist. 



(i) Unhealthy plants usually contain more hydrocyanic acid than 

 healthy ones. The unhealthy condition may be due to malnutrition, to 

 improper transpiration, to insect attack, or to other causes. It is possible 

 that under such conditions the plant produces more glucosid for the sake 

 of the stimulating honnones in it. 



