BLASTOGENIC VAKIATIONS. 185 



if you sow the seed of the Blenheim Orange and raise 

 young apple trees, you will not get a Blenheim Orange. 

 All your plants will be different, and probably not one 

 will give you apples with the peculiar excellence of 

 the parent. If you want to propagate your Blen- 

 heim Orange and increase the number of your 

 trees, you must proceed by grafting or by striking 

 cuttings." 



In the face of such evidence as this, it seems impos- 

 sible for Professor Pearson to maintain his belief that 

 the function of sex in evolution " is not the production 

 of greater variability." At the same time, his results 

 above quoted show the incorrectness of the view some- 

 times held, that variability is quite insignificant in 

 asexually, as compared with that in sexually, reproduced 

 forms. Statistically measured, it is only 10 to, say, 50 

 per cent, less, though when this amount is translated 

 into differences of foliage and flowers, or of quality of 

 fruit, it seems at first sight much more considerable. 



Bud-Variation. Considerable variations may arise 

 asexually in cases of so-called bud-variation. This 

 term was used by Darwin to designate the sudden 

 changes in structure and appearance which occasionally 

 occur in the flower-buds or leaf-buds of full-grown 

 plants. Such changes are known to gardeners as 

 sports, but, as we have already seen, this term is now 

 used to include all suddenly arising discontinuous vari- 

 ations. 



One of the best known and most striking instances of 

 bud-variation is that of the nectarine, which occasion- 

 ally appears on full-grown peach trees which have pre- 



