430 EXPERIMENT STATION RECORD. IVol. 43 



The fixation of free nitrogen by green plants, F. B. Wann (ScicnGe, 

 n. ser., 51 {1920), No. 131 4, pp. 2Jp, 2.J8).— Attention is called to differenc-cs of 

 opinion regarding the ability of chlorophyll-containing plants to utilize the 

 uncombined nitrogen of the air. Experiments were carried on in the New 

 York State Collie of Agriculture laboratory with seven species of grass-green 

 algae, and with the exception of one (Piotococcus sp.), all were isolated from 

 the soil and used in pure cultures. 



The cultures were grown in Kjeldahl flasks containing 150 gm. of a mineral 

 nutrient agar. The full nutrient solution contained 0.5 gm. ammonium nitrate 

 per liter, and in the various series of the experiments this source of nitrogen 

 was replaced by anmionium sulphate, calcium nitrate, asparagin, glycocoll, and 

 urea. In all cultures, approximately equal quantities of nitrogen were used 

 with and without 1 per cent glucose. In the cultures receiving ammonium 

 nitrate, calcium nitrate, and ammonium sulphate, mannite was also used. 



At the end of the growing period, which was from five to seven months, the 

 cultures were analyzed for total nitrogen, and it was found that in the urea, 

 glycocoll, asparagin, and ammonium sulphate series no marked increase or 

 decrease of nitrogen occurred in the presence of either glucose or mannite. 

 Marked increases were found, however, in both ammonium nitrate and calcium 

 nitrate media in the presence of glucose, the increase in total nitrogen ranging 

 from 17 to 55 per cent. Where mannite replaced glucose in nitrate media 

 there was no indication of fixation and in the absence of both glucose and man- 

 nite there was only a slight increase over the checks. Fixation was not con- 

 fined to any one of the species, all seven sliowing the ability to use free nitro- 

 gen. The amount of fixation, however, varied with the different species and 

 seemed to be related to tlie intensity crf growth. 



In experiments carried on in 1919, there is said to have been a denitrification 

 of one species when grown on nitrate media in the presence of mannite. How- 

 ever, the same species in the presence of glucose increased the total nitrogen 

 content of the culture. There was also a slight indication of denitrificafion 

 with this species on nitrate media in the absence of both glucose and mannite. 



Nitrophile plant formations around manure heaps, J. Fkodin {Bot. 

 Notiser, No. 6 {1919), pp. 27i-277).— This is an account of the belts of vegeta- 

 tion growing in the vicinity of manure heaps, with some account of the relations 

 thereto of nitrogenous compounds. 



The production of fat in plants, T. Bokobny {Bot Ccntbl., Beihefte, S5 

 (1917), 1. AM., No. 1, pp. 111-181). — An account is given of the determination 

 of the production of fat in plants, particularly yeast in tlie presence of nutrients. 



Carbon-nitrogen ratio in relation to plant metabolism, A. M. Gurjae 

 {Ahs. in Science, n. ser., 51 {1920), No. 1318, pp. 351, 352). — According to the 

 author, the supply of nitrogen determines the relative proportign of carbohy- 

 drates and proteins in the tomato plant. Changes in these proportions are 

 accompanied by marked changes in the metabolism of the plant. Although the 

 carbon-nitrogen ratio may be as high as 19 and as low as 2, fruiting was found 

 to take place only between the ratios of 4 and 6. Respiration was influenced 

 directly and photosynthesis inversely with the carbon-nitrogen ratio. In nitro- 

 gen starved plants, catalase activity was not parallel to" respiration but varied 

 inversely with it. Under etiolation, the high carbohydrate plants were reduced 

 to protoplasmic respiration sooner than the low carbohydrate plants, which is 

 said to mean that the enzym system of the former fails to make available the 

 starch reserve. The observations on tomatoes, whicli were confirmed by similar 

 data obtained with turnips and radislies, are said to empliasize the importance 

 of determining the proper carbon-nitrogen ratio for all economic plants. 



