52 THE NATURE AND WORE OF PLANTS 



all of the Wcarm season, absorbing the substances 

 set free by the decay of other plants. At certam 

 times they send up the large branches which are 

 ordinarily know as mushrooms, which bear innumer- 

 able spores, and which reproduce the plant. The 

 mycelium, or mass of tubes, spreads rapidl}^ under- 

 ground, and the mushrooms may appear in the most 

 unexpected places and very suddenly. Like the 

 roots of the higher plants, they are driven upward 

 through the soil with great force, and may be seen 

 to lift stones, large pieces of wood, or heavy clods of 

 earth. Mushrooms have been known to grow up 

 under the stones of the sidewalks in village streets, 

 lifting them from their places and seriously dis- 

 arranging the pavement. 



58. Ahsorptio7i and fixation hy the algce, and bac- 

 teria. — Many of the plants of the lowest groups 

 are completely submerged in water in which their 

 food is dissolved, and as a consequence they absorb 

 food over their entire surfaces. Some of these, espe- 

 cially the bacteria, are in the form of small globular 

 or egg-shaped cells, or in the form of rods joined 

 together in a chain, all floating freely in the water. 

 The function of fixation is clearly absent in most 



