194 FLOWERLESS PLANTS 



pense of the atmosphere, and the moisture and dust which it 

 bears to them. In course of time they make the hardest rock 

 habitable for higher organisms, and thus show, once^more, that 

 in nature the smallest things are often of the greatest importance. 



45. Bacteria 



(Schizomycetes). 



A. The Structure of the Bacteria. — 



1. These plants are the smallest organisms known. ^lany 

 of them are so small that 25,000 of them arranged end to end 

 would not measure more than an inch. If examined under the 

 microscope, it is found that each of them is made up of one cell. 

 They assume various shapes: some appear like globules, some 

 like short sticks, others are long and straight, others, again, 

 spirally wound. They are generally called "bacteria " or "bacilli", 

 words meaning sticks or little rods. 



2. Under favourable conditions they multiply by splitting in 

 two. And they multiply at such an enormous rate that, if the 

 conditions remained favoural)le, one such minute thing would in 

 the course of less than six days swell to a mass larger in bulk 

 than the earth itself. This is, of course, never possible, for the 

 food they require for their incessant multiplication would soon 

 fail. But we can see from this example the tremendous rate at 

 which they increase. If the conditions under which they live 

 become unfavourable, they assume a shape that enables them 

 to lie passive until the conditions again become favourable for 

 the continuation of their life. 



3. We have seen how small these plants are, and we can now 

 understand that dry Bacteria can be easily whirled up by the 

 wind and carried away thousands of miles. As invisible dust 

 they are present everywhere in the atmosphere, and return to the 

 earth when the air becomes calm. 



B. The Activity of the Bacteria. — 



1. The Bacteria, like the Fungi, lack chlorophyll; they are, 

 therefore, dependent u[)On ready-made nourishment, animal or 

 vegetable, which they ohtain easiest in decaying matter. 



