INTRODUCTION. 



493 



Compositae. But the most common case is where the ovules spring from undoubted 

 leaves— the carpels — and usually from their margin, like pinnae from the leaf (this is very 

 clear, e.g. in C^cas), more rarely from their upper (or inner) surface (as in Butomus, 

 Akebia^ Nymphoea, &c.). If the ordinary morphological definitions are applied to these 

 relationships, we should have in the first-named case ovules of an axial nature, or they 

 would be metamorphosed caulomes^; where they spring laterally from the axis, they 

 would have to be considered as metamorphosed entire leaves ; and where they proceed 

 laterally from the margins of carpellary leaves, as metamorphosed pinnae. For those 

 ovules which spring from the surface of carpels there is no clear analogy with any 

 purely vegetative structures [i.e. with any that do not subserve the purpose of fertilisa- 

 tion) ; though in this case we may be reminded of the sporangia of Lycopodlum. The 

 ovules, finally, of some Gupressineae, which appear to have an axillary position on the 

 carpels, have not yet been sufficiently investigated with respect to their true relationships. 

 In some cases the morphological interpretation is supported by malformations which not 

 unfrequently occur. Cramer, to whom we are indebted for an admirable investigation 

 of this question, has shown that the ovules of Primulaceae and Compositae, which arise 

 laterally beneath the apex of the axis of the flower, become gradually transformed into 

 entire leaves of the ordinary form ; and that in the same manner the ovules of Delphi- 

 nium, Melilotus, and Daucus, which spring laterally from the margins of the carpellary 

 leaves, may become developed into ordinary parts of the lamina, as laciniae or leaflets. 

 It appears on the other hand significant that nothing of the kind has yet been 

 observed in those ovules which have been interpreted above as metamorphosed por- 

 tions of the axis. The development not only of normal, but still more plainly that of 

 abnormal ovules, shows further that a morphological distinction exists between the 

 nucellus on the one hand and the funiculus together with the integuments on the other 

 hand. In those anatropous ovules which may be regarded as metamorphosed leaves or 

 parts of leaves, the nucellus makes its appearance as a new lateral structure inserted on 

 the rudiment of the ovule, and when this latter becomes developed in a leaf-like manner 

 it appears as an outgrowth of the surface of the leaf. This fact, the morphological 

 importance of which was first insisted on by Cramer, is however not universal, as is 

 especially shown in the development of the ovules of Orchideae, the nucellus of which 

 unquestionably corresponds to the apex of the entire ovule, although it becomes 

 anatropous by subsequent curvature ; still less possible does it appear to consider 

 the nucellus of the orthotropous ovule of Taxuj and the Polygonaceae as a lateral 

 formation, since it is obviously an elongation of the apex of the floral axis (see Angio- 

 sperms) '^. 



The Carpellary Leagues are the foliar structures of the flower which stand in the 

 closest genetic and functional relationship to the ovules. They either produce and 

 bear the ovules, or are constructed so as to enclose them in a chamber, the O'vary, and to 

 form the apparatus for the reception of the pollen, or Stigma. The varying morphological 

 significance of the carpellary leaves is clearly seen by a comparison of the genera Cycas 

 and Juniperus. In Cycas the carpels resemble the ordinary leaves of the plant, and the 

 ovules are produced on theii* margins and remain ' entirely exposed ; in Juniperus the 

 ovules spring from the floral axis itself, corresponding, even in their position, to a whorl 



* Cramer, Bildungsabweichungen bei einigen wichtigeren Pflanzen-familien, u. die morpholo- 

 gische Bedeutung des Pflanzeneies (Zurich 1864), is inclined to consider all ovules as metamorphosed 

 leaves or parts of leaves. To this view I have already expressed some hesitation in the first edition 

 of this book ; the description here given, which differs from the earlier one, is derived as much as 

 possible from direct observation. 



^ [In view of the very great variety of position in the development of the sporangia (including 

 pollen-sacs and ovules) it will be on the whole simpler and more satisfactory, as Goebel has 

 suggested, not to attempt to assign them to the categories of phyllome and caulome, but to regard 

 them as organs having a morphological value of their own.] 



