218 THE PHENOMENON OF 



development may be. It is to this carbonaceous appa- 

 ratus of the cell that the entire structure of the plant 

 owes its external and internal combination and solidity ; 

 but it is at the same time the cause of the gradual 

 fixation of the product, the relative absence of motion, 

 which distinguishes the vegetable structure, in contrast 

 to the internally and externally more mobile animal 

 organism. It is remarkable that the most striking of all 

 the phenomena of motion of plants, the swarming move- 

 ment of the gonidia and spermatozoidia, occur in such 

 cells as are either yet without their cellulose coating, or 

 which never acquire one. Thus, consequently, the life of 

 the plant becomes fettered by the vegetative process itself ; 

 the continuous secretion of cellulose, and the thickening 

 of the cell-wall caused thereby, obstruct more and more 

 the intercourse with the outside, as in like manner the 

 accumulation of highly carbonized deposits in the interior 

 of the cell- contents obstructs the internal movement. 

 Thus all vital activity must at last come to a pause, 

 unless this entombing and suffocating process of formation 

 becomes opposed by a dissolving and emancipating pro- 

 cess. It is just this which we have sought to examine 

 in the foregoing pages ; we have seen it make its appear- 

 ance at a definite period in those parts which are destined 

 to carry on or repeat the development, destroying pre- 

 ceding constructions, and making space for new forma- 

 tions, more or less interrupting the old course of com- 

 pletion, and often causing the life to turn off in new 

 directions. We have seen that the solid cell-membrane 

 becomes soft again, bursts, or dissolves away ; we have 

 seen the starch dissolved, the fixed oils vanish. But the 

 most important occurrence in this process of destruction 

 is not merely a solution of that which had become solid, 

 not merely a process of transformation of the substances 

 secreted in the formative process, into new material for 

 structure (e. g. starch into dextrine and sugar), but, at 

 all events in part, an actual destruction (combustion) 

 of the highly carbonized substances present in excess, 



