188 



PRINCIPLES OF PLANT-TERATOLOGY. 



with the midrib of the main lamina ; a phenomenon 

 which varies only according to the idiosyncrasy and 

 needs of the organ or organs exhibiting it. 



One of the most remarkable of known abnormalities, 

 and at the same time one of the least easy to explain 

 offhand, is the St. Valery apple ; at the place from 

 which the fruit derives its name, a tree, termed variously 

 "Pommier sans fleurs" or "Pyrtis dioica Willd.," bore 

 flowers all of which had sepals in place of petals and 

 not a single stamen ; at a later stage the " fruit " was 

 seen to consist of two " cores," placed one above the 



Fig. 135. — Pyrus Mains var. (St. Valery Apple). Carpellody of the 

 stamens. (From Masters, after Tillette.) 



other. The appearance is presented of a double-tiered 

 apple having a constriction between the two tiers. At 

 the apex the sepals occur in the ordinary way (fig. 135). 



That this structure is due to proliferation of the 

 normal fruit, as some have hinted, seems placed out 

 of court by the fact that in the closely allied species, 

 viz., the pear, when proliferation occurs the normal 

 inferior ovary always completely disappears, and there 

 are never two sets of seed-bearing " cores " as in the 

 St. Valery apple. It is very unlikely that, if the second 

 tier of carpels were borne on an extension of a central 

 axis, the apple would behave so differently from the 

 pear in this respect. On the other hand the view that 



