ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 355 



the germination of oily seeds. He concludes that these seeds are capable 

 of transforming substances of the group CH 2 into substances of the 

 group CHOH by the fixation of oxygen. He found the plant most con- 

 venient for these experiments to be the castor-oil plant. 



Recent Researches on Nitrification.* — Prof. R. Warington gives 

 the following summary of recent researches on nitrification. 



" During recent years, the chief investigations on the character and 

 properties of the nitrifying organisms have been carried out in Wino- 

 gradsky's laboratory in St. Petersburg, none having been executed in this 

 country. Formerly, investigators have been unable to obtain pure 

 cultures of the organisms ; their chemical characters had, however, been 

 studied, as their capacity for growth in a purely mineral solution allowed 

 of their separation from most of the other organisms in the soil. It had 

 been found that the process of nitrification consisted of two distinct 

 pieces of chemical work, effected by two agents, which could be separated 

 from each other ; by the first (the nitrous organism) ammonia was con- 

 verted into a nitrite ; by the second (the nitric organism) the nitrite was 

 oxidised to nitrate. These facts were first ascertained at Rothamsted. 



" To isolate the nitrous organism from soil, Winogradsky commences 

 by a series of cultures in an inorganic solution containing an ammo- 

 nium salt and the ash constituents of plant food. From this solution, 

 cultivations on solid media are started. For some years silica jelly 

 was employed, but Omeliansky now prefers plates of magnesia-gypsum 

 saturated with the mineral solution already mentioned.f To isolate the 

 nitric organism, the preliminary cultures are made in a solution con- 

 taining sodium nitrite and ash constituents. As a solid medium, purified 

 agar, with nitrite and ash constituents, is made use of. The fermentable 

 constituents of the agar have been previously removed by Beyerinck's 

 method. 



" Winogradsky has examined soils from many parts of the world. 

 He finds but one nitrous and one nitric organism in any soil. The nitric 

 organism is everywhere the same species. The nitrous organism may 

 vary. In Europe, North Africa, and parts of Asia, the same species 

 occurs, with variations in size and in tendency to adopt a zooglcea or 

 motile condition ; the latter condition displays the greater chemical 

 energy. The nitrous organism from Java is a distinct species, having 

 an extraordinarily long flagellura. The organism from South America 

 and Australia is generically different ; it is a giant coccus. A few other 

 investigators have described different nitrifying organisms, but the 

 evidence adduced has in some cases proved erroneous, and is in other 

 cases as yet insufficient to warrant its acceptance. 



" Winogradsky had proved by quantitative experiments that the 

 nitrous organism derives its carbon from carbonic acid ; the nitric 

 organism possesses the same power. As both organisms flourish in 

 darkness, the energy necessary for the construction of organic matter 

 out of carbon dioxide and water is apparently derived from the oxida- 

 tion, respectively, of ammonia or a nitrite. Later experiments have 

 shown that the carbonic acid is, in every case, probably taken from a 

 supercarbonate. The nutrition of the bacteria which exist with the 

 nutrifying organisms in a mineral solution requires further study. 



» Proc. Chem. Boo., xvi. (1900) pp. 65-7. f Cf. this Journal, 1899, p. 544. 



2 B 2 



