484 MORPHOLOGY. 



identity of the leaf-form and of the stem-form be ad- 

 mitted. 



Structure of the ovule. The nature of the ovule and of 

 its coverings has been a fertile source of controversy. 

 The teratological data bearing on this subject have been 

 given at pp. 262 272. These data strongly support 

 the notion of the foliar nature of the coatings, and of the 

 axial nature of the nucleus, taking leaf and axis either 

 in the ordinary sense, or as modifications one of the 

 other. It has been shown that the ovular coats may 

 themselves become carpels, and that ovules may be 

 developed upon ovules, p. 268. Whether the intra- 

 carpellary siliques of Cheiranthus, not uncommonly 

 met with (p. 182), are instances of ovular transmutation 

 may be open to doubt. 



The axial nature of the nucleus has been inferred from 

 its position, mode of growth, and from its occasionally 

 lengthening into a leafy or even a floriferous shoot. 

 Probably it may occasionally be invested by sheathing 

 coats, more analogous to tubular processes from the 

 receptacle, than to foliar organs, as is the case in 

 Welwitschia. The discussion of this matter, however, 

 pertains rather to normal morphology than to tera- 

 tology. 



Morphology of conifers. The nature of the pseudo-leaves 

 of Sciadopitys, and probably of other Conifers, is illus- 

 trated by teratology, as also is the true constitution of 

 the scale of the cone (see pp. 192, 245, 352), though 

 it must be admitted that little or no light is thrown 

 on that much-contested point the true nature of the 

 ovule of Gymnosperms. 



Relative position of organs. When organs are con- 

 sidered, not separately, but in their relations to each 

 other, the appearances presented are referable to 

 similar causes. Thus, the separation of parts usually 

 united has been shown to diepend on an excess of 



