CHAPTER XII. 



THE MAINTENANCE OF BODILY FORM. 



Every plant is capable of attaining and maintaining a 

 specific form, which is not permanently altered by the direct 

 action of external forces, and is dependent upon the nature 

 C)f the plant itself 



187. Naked cells. — If the plant consists of a single mass 

 of naked protoplasm, it may assume a spherical or ovoid 

 shape (fig. i68). In attaining this form the physical forces 



Fir., r6S. — Zoospores of various forms, swimming in water by means of one or more 

 cilia, ^-J , BoirydiuJi! : B, Th-aparnaldia ; C, Coleocliaiie ; JJ, Qidcgoniiun. 

 Higlily magnified, — After Kerner, 



constituting surface tension pla\' a fiart, but the form is deter- 

 mined chiefly by internal forces inherent in the protoplasm. 

 This is particularly well shown when such organisms extend 

 delicate protoplasmic threads, the cilia, and maintain these 



147 



