LIFE HISTORIES OF FAMILIAR PLANTS 



The flowers of the broom do not appear in 

 pendent racemes but in sohtary ones, or occasion- 

 ally in twos, along the wiry branches. A pendent 

 raceme of flowers, like that of the laburnum, on 

 these erect branches would be altogether in the 

 wrong place, so we find the flowers arranged in 

 orderly fashion on the rigid branches for the bees 

 to see them. Thus the broom, owing to difference 

 of habitat, has developed on quite other lines than 

 its near relative, the laburnum. 



Having thus accounted for the difference 

 between the laburnum and the broom, the gorse 

 now remains for consideration. Why has this 

 close relation of the broom, both of which thrive 

 in identical situations, found it necessary to arm 

 itself so elaborately ? The answer to that question 

 is, I think, that the difference came about origin- 

 ally when the two species first diverged from the 

 ancestral type. 



Assuming that, in the natural and unceasing 

 variation of living things, some of the offspring of 

 the remote family ancestor happened to develop 

 in their tissues a bitter property that made them 

 distasteful to herbivorous animals, such individuals 

 would be more likely to survive than those which 

 were not so protected. This protective feature, 

 since it conferred an advantage on those individ- 

 uals that preserved it, would be intensified in 

 future generations, and in that manner the broom 

 would slowly evolve as a distinct species, and 

 perfect its acquired protection. The dwarfing of 

 its leaves and the carrying on of their functions by 



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