THE BLUE-GREEN ALG^ (CYANOPHYCE^) 181 



others (Fig. 152) is spherical in its general form. It has a 

 well-defined wall, the cell- wall, inside of which is the living 

 substance of the plant, the protoplasm. Although in higher 

 plants the protoplasm is clearly divided into different parts, 

 — cytoplasm, nucleus, and cJiloroplasts (Sect. 8), — in Grlceo- 

 capsa these different parts are not evident. The protoplasm of 

 G-loeocapsa is granular, and there is a blue-green stain distrib- 

 uted throughout it. It is only when these plants are massed 

 together that the characteristic blue-green color is seen. In a 

 single plant this coloring matter is 

 present in such small quantities that 

 when observed under a microscope the 

 color is not easily detected. 



The living protoplasm builds the 

 wall that surrounds the inner part of 

 the cell, but the wall itself is not alive. 

 Some of the water in which Crloeocapsa 

 lives is absorbed by the wall, which 

 causes the older outer parts to swell, 

 thus producing layers of jelly-like 

 material around the protoplasm and 

 the inner cell wall. Also through the 

 wall the food material is absorbed. 

 Even with the small amount of chloro- 

 phyll and blue pigment present in one of these plants photo- 

 synthesis (Sect. 17) can be carried on. Since the plant lives 

 in stagnant water, in which there is much decaying organic 

 matter, it is not impossible that it may absorb and use directly 

 as food some of these decaying organized foods. In times of 

 drought these plants may become dry, although, being pro- 

 tected by means of the heavy gelatinous covering, they dry 

 very slowly, and when favorable conditions again come they 

 may continue to grow. 



have the student attempt to find a good specimen without any notion as to 

 what single-celled plants are. Individual studies will then be more intelligible 

 and more successful. 



Fig. 152. Gkeocapsa, one 

 of the simplest of the blue- 

 green algse. Magnified 300 

 times 



A-H, successive changes in 

 the development of new in- 

 dividuals from a parent cell 



