HOW PLANTS MABKY. 81 



they join and coalesce with one another (c and d 

 in the figure). The contents of one cell pass 

 into another (at e), and the two form a sort of 

 egg (/), which lies quiet for a while, and then 

 buds out into a new thread or hair-like plant by 

 division. In this strange process we have the 

 beginning of sex the first hint of plant and 

 animal marriages. 



What is the meaning and good of it? Why do 

 the plants act thus ? That question we don't yet 

 quite understand, perhaps ; but this seems to be 

 in part at least its reason. Protoplasm requires 

 to be kept, as it were, perpetually young and ever 

 fresh ; it cannot afford to lose its elasticity and 

 its plasticity. If it does, it grows old in time 

 and dies. To prevent this misfortune, and the 

 death of all things, plants and animals have 

 invented all sorts of curious expedients; for 

 example, the protoplasm of a living cell some- 

 times breaks out of the cell- wall, and undergoes 

 a process which is called " rejuvenescence," or 

 growing young again. It lies quiet for awhile in 

 its free condition, and then begins to build up a 

 new wall afresh for itself. It seems by the 

 process of breaking out to have gained for itself 

 a new lease of life, as we ourselves often do by 

 a trip abroad or change of scene and air and 

 occupation. However this may be, it is certain 

 at least that the union of two cells often produces 

 a fresher, stronger, and more vigorous young 

 one than can be produced by mere division of a 

 single cell. In some way or other, when a 

 plant or animal reaches maturity, and arrives 

 at the limit of its own growth, it produces 

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