Oct. I, I9I9 Notes on the Composition of the Sorghum Plant 29 



VII.— SUMMARY 



(i) Three varieties of sorghum cane were used for studying the pro- 

 gressive development of the plant and the chemical composition of the 

 various parts of it. 



(2) The relative proportion of leaves, seed heads, and clean cane by 

 weight in both the fresh and the partially dried condition was deter- 

 mined for one season. 



(3) Considering the whole plant, there was found to be a continual 

 increase in dry matter up to maturity. The percentage of crude fiber 

 decreases at practically the same rate as that at which the soluble car- 

 bohydrates increase. The crude fat, ash, and protein percentages re- 

 main almost constant throughout the periods of growth studied. 



(4) The computation of the total quantities of each constituent 

 present in the plant at the various stages of growth brings out the fact 

 that this plant builds up during the earlier part of the season its cellular 

 structure of fiber, protein, and mineral matter, and that the later stages 

 of gro\vth consist in the filling up of these tissues with carbohydrates 

 (starch in the seed, sugars in the stalk). 



(5) No evidence was found which would indicate that the leaves are 

 deprived of their carbohydrates to supply the stalk, at least during the 

 periods of growth studied. The older the plant, the higher is the feeding 

 value of the leaves. 



(6) The maturation of the seed heads consists almost entirely in the 

 filling out of a fiber and protein framework with starch. 



(7) There is a considerable accumulation of mineral matter in the 

 leaves, due probably mostly to calcium and silicon. 



(8) Large quantities of juice were employed in isolating and identify- 

 ing the nonsugar solids. Equal volumes of alcohol threw down a pre- 

 precipitate which consisted of three portions: (a) proteins, (b) cellular 

 material in suspension, arising from the crushing of the fiber in the 

 mills, and (c) true gums. 



(9) The gums are complexes of galactan and pentosans, with about 20 

 per cent of mineral matter, principally calcium, magnesium, and 

 potassium. 



(10) The organic acids found in sorghum juice are aconitic, malic, 

 citric, tartaric, and oxalic. 



(11) Nonprotein (amid) nitrogen is very high in sorghum juice, even 

 in mature cane. This is an important contributing factor in the diffi- 

 culties of defecating sorghum juice for either sirup or sugar production. 



(12) The following nitrogenous substances were identified in sorghum 

 juice: 1-leucin, d-1-asparagin, glutamin, cystin (?), and aspartic acid(?). 



(13) The juice of suckers has a composition similar to that of the main 

 canes at the same stage of maturity. They are, however, usually from 

 one to three weeks behind the main canes in maturity. 



