58 GENERAL BIOLOGY 



sides is chlorophyl, and the transparent capsule inclosing 

 the whole is the cell wall. The whole plant thus enveloped 

 is a single cell. 



Well down in the angle toward each end of the crescent 

 will be noticed also a round droplet of watery fluid called 

 a vacuole, in which, under high magnification may be seen 

 suspended some minute crystals in continuous (Brownian) 

 movement. 



If from a freshly growing Closterium culture a number of 

 individuals be mounted and examined, they will be found 

 to differ considerably in size and in appearance at the trans- 

 parent middle crossband where the nucleus lies. Some of 

 the larger ones will show a broader clear area there, or an 

 indentation of the cell wall at each side, or a constriction 

 extending entirely across the cell, cutting it more or less 

 deeply into two parts, as indicated in figure 43. Closely 

 examined, this process will be seen to be initiated by the 

 division of the nucleus into two parts, one of which passes 

 to each side of the cross band and into the 

 edge of the chlorophyl. The deepening 

 constriction thus divides the mass of proto- 

 plasm, and forms two smaller cells out of one 

 large one. Each of the smaller ones, before 

 the separation, is lacking in the crescentic 

 symmetry of the grown plant, the newly 

 FIG. 43. Divi- formed end being blunter, lacking chlorophyl 



sion in Clos- , 



terium-.succes- and vacuole, and having the cell wall thin 



sive stages. . 



and not symmetrical with the other end. 

 Reflecting on the few readily observable details of this ap- 

 parently simple process whereby new plants are produced, 

 it is obvious at once that certain of the structures seen are 

 more essential than others. It is the protoplasm that pas- 

 ses on unchanged from mother cell to daughter cells both 

 the general protoplasm of the cell-body (cytoplasm} and 



