CH. X] 



THE STONEWORTS 



433 



The plant body is more complex than in any other Green 

 Algae (Fig. 301), involving a system of long, unicellular inter- 

 nodes alternating with short nodes, all developing from a 

 simple kind of growing point. At the nodes 

 are borne whorls of determinate, unicellular 

 branches, together with ordinary elongating 

 branches and the sexual structures, while 

 colorless rhizoids form the attachment to the 

 bottom. The huge cells when young have 

 each a single nucleus, which breaks into several 

 as growth progresses, while many small chloro- 

 plasts are arranged with pavement-like regu- 

 larity around the wall. In such great cells, 

 sometimes three inches long, the stream- 

 ing of the protoplasm is strikingly ap- 

 parent, on which account these plants, 

 especially the more delicate Nitella, are 

 favorite subjects 

 for studies upon 

 protoplasm in lab- 

 oratories. Some 

 kinds reproduce 

 vegetatively by 

 tuber-like basal 

 outgrowths, but 

 no forms of zoo- 

 spores occur. 



FIG. 301. - Chara fragilis. The Sexual re P r - 



Left, end of a shoot, natural size ; right, portion duction, however, 

 of shoot, with oogonium and antheridium ; X 25. 1 Kl 



(From Strasburger and Sachs.) mar Ka Diy 



elaborate. At the 



nodes occur oogonia containing each a huge egg cell, conspic- 

 uously visible to the naked eye because of its orange-red color. 

 The oogonium is enwrapped by an envelope composed of 

 spirally wound cells developed from the subjacent tissues. 

 At the same nodes occur remarkably complicated antheridia, 



2F 





