THE PATH OF EVOLUTION 



the next or recurring Spring burst into leaf. In this 

 way many of the annuals have been transformed into 

 perennials. 



With the majority of plants that are not strictly 

 annuals the propagation of the plant life is by 

 means of the scions or layers above mentioned, or 

 cuttings, as the gardener calls them. If a leaf-bear- 

 ing twig is cut off and embedded in earth, or, still 

 better, grafted upon a stem of an older but vigorous 

 plant of the same species, so that obliquely cut sur- 

 faces are held firmly in contact, the life continues. 

 If in the earth, the leaf buds are transformed into 

 rootlets which absorb nutrition from the soil, other 

 buds throw out stems that strive upwards and soon 

 form leaves, and a perfect plant is born. The grafted 

 stem undergoes less change; the cellules of the fresh 

 cut surfaces being in contact, the plasmodium of the 

 older plant cell is transferred to those of the younger 

 cutting, and the sap juice circulates through its ves- 

 sels ; the leaves of the cutting, containing chlorophyll 

 cells, secrete and form the same plasmodium that 

 they did when on the parent stock ; the cutting grows, 

 and often not only forms ultimately the entire tree, 

 but preserves the characteristics of its origin. Often 

 these characteristics, though sought for by the gar- 

 dener, are really monstrosities, so far as the physi- 

 ology of the plant itself is concerned. The soft shell 



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