124 Dr Emmons on the Influence of 



with each other through their varieties ; even in vegetables, 

 where they are susceptible of being engrafted or budded upon 

 each other, there is no tendency to coalesce, or to produce an 

 intermediate variety ; the scion of the pear engrafted upon the 

 quince is still a pear. There is, to be sure, a good reason 

 for this : the pear is developed or formed in the cellular sys- 

 tem, and really bears no connection with the quince, except 

 by the sap, which flows upwards, and passes through the 

 cellular system. The cells produced are only pear cells, yet 

 it seems that if there were any tendency in the pear to be- 

 come a quince, under any circumstances, the relation which 

 the scion bears to the stock would be a favourable one. It 

 appears necessary that a cell should be furnished from one 

 of the parents, in order to produce an intermediate progeny, 

 as is the case in the propagation of mules. But here we have 

 unfailing test of the mixed parentage, from the sterility of 

 the offspring, and although attempts have been made to prove 

 the contrary position, still there is now no position better 

 established than the one that the offspring of two different 

 species of animals are sterile. It is true that, as in many 

 other cases, there are no partial exceptions, still two mules 

 cannot propagate a race. 



Specific character is unchangeable, and species are kept 

 in consequence of this arrangement strictly apart. There is 

 an application of this fact to the products of our fields, which 

 by some farmers are supposed to undergo a change. Chess 

 is a plant which has but a slight relationship to wheat, and 

 yet the question has been discussed for years, and many in- 

 telligent men in other matters have strenuously maintained 

 that wheat changes to chess ; the change of course must be 

 by a single leap, in a single season — a complete somersault, a 

 perfect degradation of the species in a single period of growth. 

 When and where does the change begin 1 The point which 

 troubles farmers, is the appearance of chess where they have 

 sown wheat, and clean wheat too. But it is also notorious to 

 every observer, that Nature too has sown her seeds broadcast, 

 and where there is land in a condition for seeds to germinate, 

 there they will spring up; and it comes to pass, from a wise 



