AGKICULTURAL BOTANT. 527 



follow favorable conditions for reaction (as direct sunlight, normal transpira- 

 tion, etc.), these processes or some of them seem to be reversed in the plant in 

 unfavorable weather, as continued rains, etc., the respiration coefficient of the 

 ripening seed talking the value of that proper to sprouting in the same seed. 

 The facts observed are held to afford a fresh confirmation of the reversibility 

 of analytic or synthetic processes, as related here possibly to ferments. 



A physiolog-ical and chemical study of after-ripening-, Sophia Eckerson 

 {Bot. Gaz., 55 (WIS), No. 4, PP. 2S6-299).— This paper gives the results of a 

 microchemical study together with quantitative determinations of the sub- 

 stances in the embryo of species of Cratfegus at different periods during after- 

 ripening. Previous investigators (E. S. R., 28, p. 226) have shown the best 

 conditions for after-ripening of seeds of this plant, and the author followed 

 their suggestions relative to temperature and moisture. 



It was found that food was stored in the embryo in the form of fatty oil. 

 There was also considerable lecithin, but neither starch nor sugar was present 

 in embryos kept in dry storage. The i-eaction of the cotyledons was found to be 

 acid, while that of the hypocotyl was slightly basic. A series of metabolic 

 changes in the embryo was found to talie place during the period of after- 

 ripening. The initial change seemed to be an increased acidity, but correlated 

 with this was an increased water-holding power and an increase in the activity 

 of catalase and peroxidase. Near the end of the period of after-ripening a 

 sudden increase in acidity as well as in water content took place and oxidase 

 for the first time appeared. At this time the fats decreased and sugars ap- 

 peared. Hydrocyanic acid was always to be found in the cotyledons. 



The after-ripening period, it was found, could be greatly shortened by treat- 

 ing the embryos with dilute acids, such as hydrochloric, acetic, and butyric 

 acids. When treated with acids the water-holding power, the acidity, and the 

 amount of ijeroxidase increased much more rapidly and oxidase appeared much 

 earlier than in untreated embryos. 



It appears that there is a correlation between the acidity of the hypocotyl of 

 Craltegus, and its water-absorbing power, production of enzyms, and germinat- 

 ing power. 



A bibliography is appended. 



Cellulose as a source of energ-y for nitrogen fixation, I. G. McBeth (U. S. 

 Dcpt. Agr., Bur. Plant Indus. Circ. 131, pp. 25-3Jf). — From a review of the litera- 

 ture, the author considers that there are not sufBcient data to show that the 

 presence of combined nitrogen in the culture media reduces or destroys the 

 nitrogen-fixing properties of organisms which show a pronounced nitrogen- 

 fixing power in nitrogen-free solutions. On the contrary, he believes that the 

 data indicate that the nitrogen-fixing power of some organisms may be greatly 

 stimulated by the addition of nitrogen to the culture medium. 



Experiments carried on to determine the effect of ammonium sulphate upon 

 the nitrogen-fixing power of Azotobacter chroococcum and A. heijerinckii in 

 nutrient solutions indicated that the addition of 0.1 per cent of ammonium 

 sulphate to the nutrient solution increased their nitrogen-fixing power. 



Another series of experiments on the nitrogen fixation of Azotobacter asso- 

 ciated with Bacillus rossica showed that with mixed cultures in solutions con- 

 taining both dextrose and cellulose as sources of energy decided gains were ob- 

 tained over Azotobacter alone only when the solutions contamed a considerable 

 quantity of initial nitrogen and a destruction of the cellulose occurred. 



A. chroococcum and A. ieijerinckii in association with B. rossica. Bacterium 

 fimi, or B. flavigena fixed quantities of nitrogen varying from 7.72 to 11.41 mg. 

 for each 500 cc. of solution containing cellulose only as a source of energy. 



A bibliography is appended. 



