78 



The Living Things of the Earth unit i 



Fig. loi Bacteria that cause pueinnonia. The 

 photograph was taken through a microscope. 



(AiMERlCAN MUSEUM OF NATURAL HISTORY) 



bacterium which causes one kind of 

 pneumonia \\ ere magnified to the size of 

 a tennis ball, and if the man in whom the 

 bacterium lodges were magnified in pro- 

 portion, the man would be about twenty- 

 five miles tall! But bacteria are interesting 

 to man not for the way they look but 

 for what they do. Some species live in 

 man and cause disease but many more 

 are harmless or even \aluable. You will 

 read more about them in Unit VI. 



PI n LUM - BR^'OPHVTKS 



The Mosses and Their Relatives 



The second large di\ ision of flowcrlcss 

 jjlants. This group includes the mosses. 

 rhc\ look somcw hat more like the plants 

 commonly recf)gnized as plants. For one 

 thing, most of them live on land. I'or 

 another, they are always green ami, like 

 the plants you know best, are anchored 

 ro the soil. Then, too, moss plants have 

 simple le;ncs and rootliK'C and stemlike 



Fig. 102 thyscuiiiitriuin, a tiny moss that you, 

 may find in your garden. It is less than one-half 

 inch high, (hugh spencer) 



parts. Mosses range in size from less than 

 one-eighth inch to more than one and 

 one-half feet high. 



Mosses gro\\- almost everywhere ex- 

 cept in salt water. There are vast bogs 

 of one kind of moss known as Sphagmnn. 

 The sphagnums are among the largest 

 of mosses, having^ a stemlike part that 

 grows to be many inches long. Stems and 

 leaves are constructed so that they absorb 

 water like a sponge and for this reason 

 some kinds were formerly used for dress- 

 iniT wounds. The greatest usefulness of 

 sphagnums arises from the fact that 

 w hen they gro\\- in w arcr, the plants do 

 not decay when they die. The accumu- 

 lated dead plants become w hat is known 

 as peat. Peat accumulations many feet 

 deep are common. After draining the 

 bog, the peat can be dug out in small 

 squares, dried and used as a fuel. 



