LABURNUM, BROOM, AND GORSE 



the stemS; would probably follow later according 

 as such modifications helped the progress of the 

 species. 



Such variations from the parent type are 

 always taking place^ for no two individuals of a 

 species are exactly alike. It follows^ therefore, 

 that some other individuals of the ancestral stock 

 may, in the course of such variations, have 

 developed leaves or leaflets with a tendency to 

 produce sharp points or edges that irritated the 

 soft noses of depredating animals. Again, such 

 individuals would derive protective advantages by 

 means of this variation, and by the natural law of 

 heredity such advantages would be handed down 

 to their offspring, and be further evolved and 

 strengthened in the generations that followed. 



So the gorse, like the laburnum and the broom, 

 is probably a descendant of the same common 

 ancestor, but a descendant which has gone on 

 modifying its structure in a different direction 

 until its trefoil leaves have entirely disappeared ; 

 for although we cannot say just what the ancient 

 type was like, yet I think it would be fairly safe 

 to assume that it possessed yellow pea-flowers and 

 leaves of three leaflets. Probably the still more 

 remote ancestor of the Pea-flower family had more 

 than three leaflets, and these pinnately arranged 

 on the stalk, as in the vetches ; for I am inclined 

 to think that the trefoil leaf is a development from 

 the pinnate form. Indeed, there are species 

 which bridge over the trefoil group to the many- 

 leafleted vetches, such as the bird's-foot trefoil, 



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