THE STONEWORTS 201 



and such fungi as the molds (Sec. 261) and water molds 

 (Sec. 262), are peculiar to plants. The question may be asked, 

 Why are coenocytes considered single cells, and not a com- 

 pound structure made up of a united mass of protoplasts repre- 

 sented by the numerous nuclei ? It is known that the nuclei 

 do not occupy fixed positions in the coenocytes, as if they 

 represented the cells of a compound structure. On the con- 

 trary, they shift with the movements of the protoplasm which 

 behaves as a unit, like a gigantic protoplast growing in differ- 

 ent directions in obedience to various stimuli, and carrying on 

 the usual cell activities. For these reasons the co3nocyte must 

 be regarded as a many-nucleate cell and not a compound struc- 

 ture or mass of protoplasts. 



ORDER 6. THE STONEWORTS, OR CHARALES 



230. The stoneworts.* The stoneworts (order Charales) are 

 the most complex of the green algse. The plant body (Fig. 192, A) 

 consists of long, jointed stems, which bear circles of lateral 

 branches at the joints. The sexual organs (Fig. 192, B, C,D) are 

 borne on these branches, but are too complicated for considera- 

 tion here. Many of the Charales are heavily incrusted with 

 lime, which peculiarity gives them their popular name of stone- 

 worts. They sometimes grow in great masses attached to the 

 bottom of ponds and shallow lakes. 



Some forms of stoneworts (Nitella), which are free from 

 incrusting lime, frequently illustrate very beautifully the move- 

 ments of protoplasm in the large cells (internodes) which lie 



* To THE INSTRUCTOR : The Charales is such a highly special group that 

 it is hardly wise to give it much attention in a general course, especially if 

 time and material is available for a more thorough study of the Confervales. 

 Nevertheless, material of the stoneworts is frequently easily obtained, espe- 

 cially in the Middle West, where it is difficult to do justice to the brown and 

 red algse, and it might be substituted for certain work in those groups. One 

 of the best accounts of the Charales will be found in Goebel, Outlines of 

 Classification and Special Morphology of Plants. 



