12 



PRINCIPLES OF PLANT-TERATOLOGY. 



flower, more or less perfect in its development. Inas- 

 much as the upper fruits entirely resemble in their con- 

 sistence and every other essential character the normal 

 one, it seems best to regard them as being constituted 

 in exactly the same way. The normal pome-fruit may 

 be regarded as composed of a central " core " (the 

 ovary) surrounded by, and congenitally fused with, 

 the abnormally elongated bases of the sepals. Cela- 

 kovsky objected to the idea that the sepals played any 

 part in the formation of the fruit of the Rosacea on 

 the ground that these sepals are perfectly organized, 

 which they would not have been had any portion of 

 them been fused with the axis below ; but he forgot 

 that this case may be quite analogous to that of the 

 .Solanaceae in which the leafy bract, although it is 

 fused for a long distance with the main axis, is yet as 

 well and fully developed as any other leaf on the plant. 

 In both cases, besides fusion, congenital elongation of 

 the leaf-base may have occurred. Strong support is 

 lent to this view by an observation of Domin's in 

 Potentilla aurea, in which the receptacle became split 

 up into a number of free sepals, the base of each being 

 furnished with stipules provided by the leaves of the 

 epicalyx, a fact which further shows the true nature 

 of this last-named, structure. The stamens and petals 

 were seated on the true receptacle or torus of the flower. 

 If the sepal-bases, as proved by this abnormality, con- 

 stitute the receptacular tube in Potentilla, it is only 

 natural to suppose that this structure is of the same 

 nature in all other members of the Rosaceae. 



Those kinds of pear-shoots, of which an extreme 

 case is described and figured in the ' Gardeners' 

 Chronicle,'* where the vegetative axis appears to 

 assume the consistence, to a certain extent at least, 

 of the "fruit," thus seeming to strongly support 

 the shoot-theory of the pome, may probably be 

 explained as follows : the shoot had, as it were, in- 

 tended to form a fruit, but, owing to certain conditions 



* 1881, part 1, p. 41. 



