CHAPTER XXII 



THE SIMPLEST PLANTS 



238. Introduction. — Many plants when full grown never 

 have mere than one cell and are so small that they can 

 be studied only through a microscope. All of these 

 minute plants have long scientific names, often hard to 

 remember, but they are the same names which the English, 

 German, or Japanese children have to learn when they 

 study these plants. 



The two plants discussed in this chapter belong to the 

 group known as the Green Alyce (Latin, algce, seaweed). 



The names of these two plants 

 are Pleurococcus (plu-ro-kok'iis) 

 and Spirogyra (spi-ro-ji'ra). 



We are now to compare these 

 microscopic plants with the bean 

 plant with its many parts com- 

 posed of hundreds of cells, which 

 is able to respire, make its own 

 food, and grow bean seeds. 



239. Pleurococcus. — Pleurococ- 

 cus is a widely distributed, 

 single- celled plant which grows in great abundance 

 upon the shady side of trees, old buildings, and rocks. 

 After a rain it is conspicuous in these places as green 

 patches. A bit of this green substance examined with 

 a microscope shows many green cells. Each plant, or 

 we may say, each cell is a somewhat roundish structure 



338 



Figure 363. — Pleurococcus. 



a, single cell; b, cell dividing; 

 c and d, groups of cells. 



