CHARALES 



109 



them though normally the presence of the stem apex inhibits their 

 appearance but if this is cut off they will then develop. This 

 behaviour is very suggestive of an auxin control similar to that 



Fig. 74. Charales. A, Nitella batrachosperma, B, Chora hispida. C, underground 

 bulbil of C. aspera. D, germinating oospore. E, protonema of C.fragilis. F, young 

 plant of C crinita. a/) = accessory protonema, z = internode, ^ = protonema, 

 r = rhizoids, rn = rhizoid node, 5 = shoot, sn = stem node, v = initial of young plant. 

 (After Fritsch.) 



found in the higher plants. The cells, which have a cellulose 

 membrane, contain discoid chloroplasts without any pyrenoids 

 together with one nucleus. Cytoplasmic streaming is very readily 

 observed, especially in the internodal cells. Sexual reproduction is 

 by means of a characteristic oogamy where light intensity plays a 



