H. BOTANY AND HORTICULTURE. 347 



ble of maintaining the growth of a plant, while the exterior 

 red rays do not possess this power; also, that in this action 

 it is by no means the luminous power, but simply the proper 

 quality of the rays, that produces the effect. 19 (7, March 16, 

 1872,90. 



CHARACTERS OF BACTERIA. 



Dr. Cohn has been prosecuting a careful series of experi- 

 ments upon the Bacteria, well-known forms of microscopic 

 bodies that are supposed to enter very largely into the pro- 

 cesses of fermentation and contagion, and he has reached a 

 number of conclusions, which in some respects differ from, 

 and in others agree with, the determinations of eminent writ- 

 ers, such as Bastian, Crace Calvert, Frankland, etc. He thinks 

 he has abundant evidence to prove that Bacteria and Peni- 

 cillium are independent of each other, that the former can 

 not be developed from the latter, that the latter does not pro- 

 duce putrefaction, and, finally, that the germs are destroyed 

 at a temperature of.l76Fahr. The other facts reached by 

 Dr. Cohn in regard to the Bacteria are the followinGr: First. 

 Bacteria are cells which, as far as we can judge, contain a 

 protoplasmic, and, very probably, nitrogenous matter, in the 

 form of strongly refractive granules, which have a decided 

 outline, apparently without cellulose, and a motion apparent- 

 ly not produced by cilia. Second. The protoplasm of Bacte- 

 ria cells is colorless, although of a different refractive power 

 from water, so that, whenever existing in large numbers in 

 water, they impart a turbid appearance to it. This turbidity 

 is therefore a microscopic indication of the development of 

 Bacteria. Third. Bacteria cells multiply by transverse di- 

 vision into two equivalent daughter cells, which again divide 

 transversely. This multiplication depends, on the one hand, 

 upon the nutriment received, and, on the other, upon the tem- 

 perature, and ceases entirely at a low temperature. Fourth. 

 Bacteria assimilate nitrogenous combinations, from which 

 they form protoplasm. Following the analogy of the fungi, 

 it is probable that they take up by endosmosis the liquid al- 

 buminous combinations dissolved in water. According to 

 Pasteur, they can form their nitrogenous cell matter out of 

 ammonia combinations, but how far they can assimilate other 

 nitrogenous matters is not yet established. Fifth. Bacteria 



