§ 1] UPON THE RATE OF GROWTH 299 



ters they digest, still it is only recently that the fact that green 

 plants in general can make use of organic compounds has been 

 recognized. Bokoeny ('97) has lately brought together the 

 evidence which makes this conclusion certain. It appears that 

 in the presence of organic solutions some algae may grow for 

 half a year in the absence of carbon dioxide ; and the potato 

 plant may, even in the dark, store up starch in its tubers in the 

 presence of rich organic food. Nitrogen may also be gained 

 from amido-bodies ; thus, Basslbe ('87) found that his maize 

 cultures grew better in asparagin, 



COjH . CH(NH3) . CH2 • C0(NH2), 



than in potassium nitrate. Thus plants may gain their C, H, 

 O, and N from either organic or inorganic sources. 



Non-chlorophyllaceous organisms, on the other hand, have 

 long been known to gain their 



C, H, N, and O from organic ■» I '^'i-ii'?' 



compounds; indeed, it has gen- P f^i ?'^"'*' 



erally been believed that they •' 

 can gain those elements from a 



organic compounds only. Cer- 

 tain observations, however, Fiq. 8i. — a, Nitrosomonas europiBa (ni- 

 thrOW doubt upon the entire ti^i'<= bacteria from Zurich) ; b, Nitro- 



, £ iT • 1 T r ii somonas iavensis (nitrite bacteria 



correctness of this belief ; these ^^^^ j^^^, . ^^ Nitrobacter (nitrate 

 are especially the remarkable bacteriafrom Quito). Magnified 1050. 

 results gained by Winograd- ^"'^'^ Winogbadskt, from Fischee, 



,„ . I, . T Vorlesungen Uber Bakterien, 1897. 



SKY ( 90) from nitriiymg bacte- 

 ria (Fig. 8-t). This author found that the bacteria could 

 grow in a mixture of inorganic salts free of organic matters. 



Solutions free from organic matter were pi'epared by the following 

 means : The culture vessels were cleaned by boiling in them sulphuric 

 acid and potassium permanganate. The water used in the cultures and in 

 washing the vessels was twice distilled in vessels without joints of organic 

 material — the second time with the addition of sulphuric acid and potassium 

 permanganate. The magnesium sulphate and potassium phosphate, used as 

 food, were calcined ; the calcium carbonate, used in excess, was likewise 

 calcined and saturated with carbon dioxide ; finally, the ammonium sul- 

 phate was especially prepared to avoid organic impurities. The culture 

 flasks were plugged with calcined amianthus, not with cotton. The solu- 

 tions were inoculated with a mere trace of the culture containing nitrifying 



