302 PHYSIOLOGY [BoT. Absts., Vol. X, 



large quantities and is transformed into compounds which do not form an integral part of 

 the cells themselves, but are dissolved in the medium. The work on utilization of nitrogen 

 has led to the conclusion that the primary importance of nitrates is in the process of sugar 

 utilization, possibly performing an intermediary function in sugar fermentation and assimila- 

 tion in forming a sugar-nitrate complex. It is the belief of the author that Azotobacter, 

 rather than serving as an active nitrogen gatherer in the soil, may act to immobilize the nitrate 

 nitrogen and to prevent or retard denitrification. — Chester A. Darling. 



1962. Dernby, K. G., and J. Blanc. On the growth and the proteolytic enzymes of 

 certain anaerobes. Jour. Bact. 6: 419-430. Fig. 1-2. 1921. — By a series of tests upon 6 

 species of Clostridium the author determined that the optimal H-ion concentration for the 

 growth of these anaerobes was between Ph 6.5 and 7.5, or an average of Ph 7. In the pro- 

 duction of proteolytic enzymes, tryptase is probably formed; its activity is optimal at about 

 Ph 6. — Chester A. Darling. 



1963. Draghetti, Alfonso. Studio comparativo della resistenza meccanica all'alletta- 

 mento di alcune razze pure di frumenti. [A comparative study of the mechanical resistance to 

 lodging of some pure strains of wheat.] Staz. Sper. Agrarie Ital. 54: 145-180. 1921. — The 

 author starts from the assumption that the immediate condition resulting in lodging is an 

 unbalanced equilibrium between external influences and intrinsic resistance of the plant 

 tissues; thus, lodging is immediately a mechanical phenomenon. The more remote causes 

 are classified in 3 groups; (1) nitrogenous hypernutrition, (2) meteorological causes, (3) me- 

 chanical maladjustments of the culm. A fundamental cause of predisposition must be searched 

 for in the intensive selection by man, tending to modify the statics of the culm and render it 

 sensitive to adverse nutritive conditions. The author states that lodging takes place before 

 the complete development of the inflorescence, while the plant is still green, and when the re- 

 sistance of the culms is due more to the turgidity of the cells than to the differentiation of spe- 

 cial tissues. The object of the investigation was to determine (1) the existence or non-exis- 

 tence of positive or negative values to be attributed to various varieties under given cultural 

 and biologic conditions; (2) the evaluation of such characters or values as a guide for selective 

 procedures; and (3) the description from a "statical" standpoint of the ^'type plant" free of 

 racial defects. The studies were made on cuhns at the critical period of stability; the plants 

 while still green were exposed to stormy weather. Pure strains were studied, comprising 

 dwarf, medium, and giant plants as well as beardless, short-bearded, and long-bearded strains, 

 in order to determine the influence of the cross section on the resistance of the culm. The 

 following determinations were made on the green specimens, immediately as brought from 

 the field and before wilting had set in: Total weight, height of culms, position of center of 

 gravity, length, weight, diameter, and thickness of the wall of every internode, weight neces- 

 sary to determine the "flexion-breaking-point" of the inferior part of every main stalk the 

 "arrow" of inflection, the angle of flexion in degrees, the elasticity of the culm, moments of 

 inertia and of resistance, unity coefficient of breaking moment, moment of wind pressure, 

 moments due to shift of center of gravity, moments of adhesive water, moment of collision 

 of culms, torsion forces, etc. A special apparatus is described and by an integration of the 

 various factors here mentioned a formula is obtained which, unlike that of Kirsche, of 

 Schweziki-Holdfeiss, and of Albrecht, takes into consideration all factors contributory to 

 resistance or weakness, and thus approaches more the dynamic conditions to which the culm 

 is subjected in the field. Naturally all these factors are correlated with thick and thin seeding 

 and related to the photosynthetic activity of the plant. The forces acting on a cuhn may 

 be permanent and intermittent. The eff'ect of all these forces is a "dynamic moment" and 

 is equal to the product of their absolute entity by their distance of appHcation from the point 

 of the most vulnerable section. The lower internodes and the "linea di terra" are most sub- 

 ject to the effect of external forces. The length and number of successive internodes are also 

 extremely important. The static equilibriiun and the balance of the positive and negative 

 moments of the cuhn gives a value which constitutes the "index of resistance," which may 

 bear a {+), positive, or ( — ), negative, sign according to whether it defines culms respectively 



