THE SIMPLER ORGANISMS 63 



in whorls along its stem, grows apically from terminal buds, 

 and has more of the aspectof familiar plants of other groups 

 than any of the algae studied hitherto. An examination of its 

 structure (fig. 45) will reveal that its stems and its branches 

 are alike made up of alternating nodes and internodes, the 

 nodes consisting of a ring of short, closely packed cells, the 

 internodes consisting each of a single very large and long 

 cell. The branches arise from the nodes. The internodes 

 are wholly exposed. 



It is these very large internodal cells, with their consider- 

 able quantity of contained protoplasm that we will study. 

 Since they are wholly exposed to view and have more or 

 less transparent walls, it will be well to observe first the 

 movements of the living protoplasm as seen under low 

 power of the microscope. A fresh green spray may be 

 plucked from the top of the stem, placed upon one slide and 

 held flat under another laid upon it, and thus placed upon 

 the stage for observation. Focusing upon the upper sur- 

 face of an internodal cell, just beneath the roughness of the 

 cell wall will be seen the numerous oval green chlorophyl 

 bodies. At a slightly lower level, by looking intently for a 

 minute, there may be seen the streaming protoplasm, which, 

 though itself transparent, contains munute granules, by the 

 movement of which it may be recognized. These granules 

 will be observed to have a slow, flowing or gliding motion, 

 and they may be traced in a definite path of circulation 

 round about the wall of the cell. A comparison of different 

 internodal cells will show that the streaming movement 

 varies in rapidity in different ones and is much more clearly 

 seen in some cells than in others.* 



*In case Nitella be not obtainable, the closely allied Chara (Fig. 

 48) may be used for the foregoing study: but for observation of 

 the streaming protoplasm, single internodal cells will usually be 

 found only at the tips of the leaves. 



