298 Bacteria in Relation to Country Life 



tions. Both serve to teach us that in the soils of today 

 and in the soils of tomorrow, bacteria are an essential 

 factor in plant-production. 



Not the least interesting fact in connection with the 

 sulfur bacteria is the ability of a portion of them to 

 grow vigorously in bright daylight. The so-called red 

 sulfur bacteria produce a pigment that partakes to 

 some extent of the properties of chlorophyl. It has 

 been asserted that with the aid of this pigment the red 

 sulfur bacteria are able to decompose carbon dioxid 

 and to assimilate the carbon after the manner of green 

 plants. It has been shown that they are attracted by 

 light. It appears, therefore, that these organisms have 

 a two-fold source of energy, in the coloring matter and 

 sunlight on the one hand, and in the sulfuretted hydro- 

 gen on the other. 



In so far as their ability to decompose carbon dioxid 

 with the aid of sunlight is concerned, they may be re- 

 garded as allied to the minute green plants known as 

 algae. In other respects, they should be classed as bac- 

 teria. As to their distribution, and that of other sulfur 

 and sulfur-reducing bacteria, it may be said that they 

 are distributed widely. Much remains to be leatned, 

 however, of their activities in arable soils. The study 

 of sulfur compounds and their transformation in the 

 soil, as related to bacteriological factors, reveals a mass 

 of interesting facts and sheds a new light on the impor- 

 tant problems of soil-treatment and soil fertility. 



Sulfur and bacterial development. — The compounds 

 of sulfur, particularly sulfates, exert a decided influence 

 on bacterial development. Magnesiytq sulfate, coiji' 



