PLANT LIFE. 35 



to over one billion germs. Being exceedingly small as 

 well as numerous, they are found almost everywhere; 

 in the soil, water, milk, food, dust and even floating 

 around in the air. While most are harmless yet some 

 cause serious diseases of man and animals, as for ex- 

 ample : tuberculosis, typhoid fever, diphtheria, plague, 

 anthrax (charbon), glanders, foul brood of hens and 

 many other troubles. Pear blight, black rot of cab- 

 bage and cauliflower, one of the wilt diseases of 

 melons, crown gall and many other plant diseases are 

 also due to bacteria. Souring of milk is also due to 

 these omnipresent plants. On the other hand, some 

 are of great value to the farmer, in that they add to 

 the nitrogen supply of the soil, or change the sub- 

 stances in the soil into forms more available for the 

 use of crops. Mention has already been made of the 

 bacteria which make the tubercles on the roots of 

 plants of the bean family. 



Algae are also low plants but they are higher than 

 bacteria. Like them some algae have but one cell and 

 are microscopic in size, but others have many cells and 

 may attain a length of many feet. They all live in 

 water or in wet places. They contain green coloring 

 matter and are therefore able to manufacture their 

 own food and cannot exist without light. Besides the 

 green color, many have red or brown colors, and are 

 very beautiful. There are many kinds of algae, but 

 few are of much economic importance. Some of 

 the red seaweeds (erroneously called sea-mosses) are 

 edible. The kelps and rockweeds are often thrown 

 upon the beach in immense quantities and are used for 

 fertilizers. The green slimy masses in brooks, ponds, 

 watering troughs, etc., are also algae. While they 

 are harmless, yet they are useless. 



Fungi. To the farmer probably the fungi are of 

 more importance than the algae. They are plants 

 with no leaves, no true stems and no roots. They con- 

 sist of many microscopic cells festered together in fine 

 white threads which penetrate the substance on which 



