

54 



THE CORNELL READING-COURSES 



well as plants that we do not call weeds because they are being fostered. 



In the same way our 

 microscopic dust-gar- 

 den will have both non- 

 useful and useful plants. 

 In the ordinary garden, 

 weeds that are visible 

 may be destroyed with 

 a rake or a hoe. In 

 our dust garden are 

 plants that are invisible 

 to the naked eye, and 

 the gardens in which 

 they grow may be the 

 food on our table, our 

 own bodies, or the dust 

 in our houses. These 

 countless invisible liv- 

 ing organisms affect us 



_, although we cannot see 



FIG. 25. What grew tn a dust garden 



them. We ascribe the 



products of their activities to various causes. They are active and 

 powerful in bringing 

 about certain amazing 

 transformations in mat- 

 ter, but we need more 

 than the lens of the 

 human eye to detect 

 them. Since either 

 good or harm may 

 result from the presence 

 of these invisible liv- 

 ing individuals, we find 

 that it is as desirable 

 to cultivate some as to 

 exclude others. 



Glass boxes, fitted 

 loosely with glass covers 

 through which much 

 that takes place inside 

 may be seen, are shown FlG ' 26 '~ Another dust z arden 



in Figs. 25 and 26. One day these glass boxes served as garden beds. 



