20 PROPAGATION OF PLANTS. 



CHAPTER II. 

 MOVEMENT AND KEORGANIZATION OF CELLS. 



There is always a struggle in nature to right herself 

 after any disturbing cause has interrupted her ordinary 

 currents and conditions, and the propagator of plants is 

 constantly doing this, especially when multiplying plants 

 by division of cellular and woody tissues. Young and 

 active cells contain matter that not only serves for the 

 completion of the cell itself, but for the formation of new 

 cells, and it is to the latter principle that we must attri- 

 bute the ready response of vegetable structures to vari- 

 ous stimulants and irritants. When a mass of cells is 

 artificially divided or separated, as in the operation of 

 making cuttings of the stems and roots of ligneous plants, 

 or of cellular matter, as found in-many bulbs and tubers, 

 the exposed cells immediately make an effort to heal or 

 cover the wound with new cells and restore the missing 

 parts. 



A severed root may, under favorable conditions, throw 

 out new rootlets to take the place of the part removed, 

 and from the exposed cells, made in removing a branch of 

 a tree or shrub, new shoots often appear. Cuttings made 

 of young twigs strive to furnish themselves with ne\v 

 roots wherewith to gather nutriment, and in all these 

 various operations, there is a movement of cell-matter 

 resulting in the production of new cells, no matter what 

 form they may subsequently assume ; whether it be that 

 of roots, leaves, or any other of the many parts and ap- 

 pendages of plants. 



The movement of cell-matter under multifarious con- 

 ditions appears to be always in response to either a 

 stimulant or irritant, and whatever other stimulant there 

 may be present, that of heat is of paramount import- 



