species in Cultivation. 179 



or three generations they were put on the market without 

 further selection. 



Space does not permit us to treat further of Le Cou- 

 teur's and Patrick Shirreff's work. Suffice it to 

 say that they show us in a general way that wheat, barley 

 and oats^ were at that time mixtures of perfectly con- 

 stant subspecies exactly as we have seen that the species 

 of wild plants are. ' But we know as little about their 

 origin in the one case as we do in the other. 



One of the most frequently discussed questions in 

 practical horticulture is that of the origin of fruit trees, 

 especially of the modern improved kinds of apples and 

 pears. There is no doubt about the common origin of 

 these forms. The question is only whether their common 

 origin merely follows from the theory of descent or 

 whether it is historically traceable. The latter is cer- 

 tainly not the case with most of the chief types ; the past 

 history is only known with certainty in the case of some 

 of the recent sorts. 



It is to the Belgian breeder Van Mons that we owe 

 the most valuable information on this subject that we 

 possess. In the first half of the nineteenth century he 

 put many of our well-known kinds on the market.- 



^ Rye, which may be wind- fertilized, behaves differently. 



^The literature on this subject seems to be little known and is 

 difficult to get hold of : I have not succeeded in seeing the works of 

 PoiTEAU and Chandeze. The following is a list of the most im- 

 portant : 



Van Mons, Arbrcs fruifiers ou Pomonomic beige, 2 vols, 1835. 

 Quotations from it will be found in Jordan's Arbres fruitiers, 

 pp. 38 and 94.. 

 PoiTEAU, Theorie de Van Mons ou notice historiquc sur les 

 moyens qu'emploie Van Mons pour obtenir d'cxccUents fruits 

 de semis. Ann. Soc. d'Agric, Paris, 1834, Vol. 15. 

 G. Chandeze, La Theorie de Van Mons concernant la production 

 de nouvelles varietes fruitier es. Belgique horticole, 1877, p. 

 354- Bot. Jahrb., V, p. 761. 

 GoDRON, De VEspcce, II, p. loi. 



