CHAPTER VIII 



PLANT BREEDING 



SATISFACTORILY to define a species is one of the most 

 difficult questions in botany, yet if one leaves aside 

 for the moment the more abstruse considerations, it is 

 possible for the present to get a tolerable idea of what 

 we mean by a species. For instance, if we talk of 

 " Blackberries," we do not indicate a narrowly defined 

 species, for there are so many varieties of Rvbus that 

 some consider that there are really a number of species 

 more or less closely related passing under the same name, 

 while others look on the forms as all one species in a 

 scientific sense, which has a number of sub-species or 

 varieties. But if, on the other hand, we speak of the 

 common little Daisy of our lawns we are more nearly 

 indicating a true scientific species, for there is much 

 less variability in its forms, and there is not such a plexus 

 from which to disentangle our ideas of what a species is. 

 Even when we take a comparatively well-marked 

 species, like the Daisy or the red Field Poppy, which 

 cannot be mistaken for any other species, we find on 

 comparing several individuals that there are slight 

 differences in the shape of the leaves or in the hairs on 

 the stems, or in the brilliance of colour in the petals. 

 When plants which have arisen from a pure line of 

 ancestry show such differences, it is considered that 

 they are purely individual and that they depend on 

 trifling differences in the plant's environment. On 



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