ANNUAL REPORT, 1942 23 



Some of the chemical changes during normal growth are as follows: Total 

 nitrogen and organic acids decreased as the season progressed; soluble nitrogen 

 and total sugars increased. The increase in total sugars continued until the 

 middle of the season. Up to that time the trend was the same for both reducing 

 and non-reducing sugars; thereafter the main change appeared to be the formation 

 of non-reducing sugars. 



The results of the culture work in complete darkness are almost completely 

 opposite those of the control. In darkness the content of solids, total nitrogen, 

 water soluble nitrogen, organic acids, and carbohydrates decreased gradually. 



The Hemicelluloses of Forage Plants. (Emmett Bennett.) Previous work at 

 this station has indicated that a considerable difference exists in the content of 

 moisture of forage grasses. An investigation of the polyuronide hemicelluloses of 

 two species, sheep's fescue {Festuca ovina) and sweet vernal (Anthoxanthum 

 odoratum) which represent grasses of low and high moisture content respectively, 

 indicated that this difference may be due chiefly' to this group of substances. The 

 greater content of total hemicelluloses was found in the low-moisture grass, and 

 the nature of these groups in the two species was quite different. 



The hemicelluloses of each species, when hydrolyzed, yielded mainly a uronic 

 acid, 1-arabinose and d-xylose in the approximate molar ratio of 1:0.2:15.7 in 

 sheep's fescue and 1:2.9:9.3 in sweet vernal. A preliminary examination of the 

 viscosity of the hemicelluloses indicated that those from sweet vernal grass when 

 dispersed in water produced not only the more viscous system, but also the more 

 stable system. Those from the sheep's fescue for the same period and under the 

 same conditions were almost completely flocculated. It would appear, there- 

 fore, that the degree of hydration of the two products differs considerably, and 

 that the species containing the more highly hydrated product has the greater 

 original moisture content and contains the larger percentage of 1-arabinose, 



Lignin and Its Relation to Absorption of Minerals by Plants. (Emmett Bennett.) 

 Special attention has centered around the mobilizing power of isolated lignin as 

 a representative of the residual organic matter in the soil. While it is known that 

 organic matter may absorb free ions in the soil, its role as a mobilizer of ions is 

 not so well established. To determine the possibilities of lignin in this capacity, 

 a container was devised which would hold both the inorganic material (calcite) 

 and the suspension of lignin in contact with each other and allow the suspension 

 to be agitated \\ith a power driven stirrer, to renew the contact, without disturb- 

 ing the calcite. The lignin was freed from mineral acids by electrodialysis. The 

 extent of mobilization could be noted from time to time by the losses in the 

 weight of calcite. Calculations based upon such a procedure indicated that 

 mobilization did take place over a period of several months in amounts equivalent 

 to a base exchange capacity of about 175 milli-equivalents per 100 grams of lignin. 

 This phenomenon indicates that the residual organic matter as such may mobilize 

 ions from insoluble compounds. A practical application may be in the form of 

 contact depletion. 



On the assumption that the high base exchange values of soil organic matter 

 are due to previous oxidations, samples of lignin were oxidized by iodine. Iodoform 

 was obtained as one by-product. The oxidation value amounted to 175 ml. of 

 N, 10 iodine per gram of lignin. Base exchange values of the oxidized lignin were 

 about 35 percent higher than those of the control. 



Attempts were made to determine the nature of the functional groups most 

 active in base exchange activity by blocking the aromatic hydroxyl group with 

 acetyl groups. This, while not wholly satisfactory, indicated that the hydroxyl 

 groups were chiefly responsible. 



