248 MORPHOLOGY OF THE ANGIOSPERMS 



the axial theory is still largely supported in other countries where evi- 

 dence from anatomy and ontogeny is not considered or is interpreted as 

 supporting the axial theory. 



The Axial Theory of the Nature of the Inferior Ovary. Interpretations 

 of the form and extent of the receptacle under the axial theory have 

 varied greatly. In some of the earlier descriptions, only the central 

 column and the placentae were called cauline. (At that time, the ovules 

 were considered buds, and buds were believed borne only on stems, a 

 conception that strongly influenced early interpretations of ovaries in 

 general.) In later interpretations, the wall of the ovary was considered 

 axial, with the carpels merely roofing the ovular chamber and forming 

 the styles and stigmas. The Phyllospory-Stachyospory theory of ovule 

 position has revived, in part, this early interpretation of carpel nature. 



Ontogenetically, there is no structural inversion or invagination in 

 these axial forms. The meristem of the receptacle ceases to grow in 

 length, and the apex is surrounded by continuing distal growth of a 

 ring of lower tissues which surpass the apex, enclosing it in greater or 

 less degree. The lateral ring carries the primordia of the lower ap- 

 pendages to a distal position on the floral axis. The true structure of the 

 flower is shown also by vascular anatomy (Fig. 95). The stelar bundles 

 extend to the apparent top of the ovary, then inward and downward to 

 the base of the hollow, where they supply the carpels. The distal down- 

 running parts of the carpel form, in the receptacular stele, an inner 

 cylinder of inverted bundles. The carpels derive their traces from this 

 inner series. The tiansfer of stem-building activity from the apex of the 

 floral meristem to its shoulders and the downward continuation of the 

 stelar bundles are sound evidence that ovaries with this ontogeny and 

 anatomy are axial in part, but this interpretation cannot be extended to 

 all inferior ovaries. 



The Appendicular Theory of the Nature of the Inferior Ovary. Behind 

 all discussions of the nature of the inferior ovary lies the tendency in 

 all organs that stand close together to become fused. The specialized 

 flower, with its appendages in close whorls, usually shows extensive 

 fusion, both connation and adnation. Involved in the adnation are usu- 

 ally the calyx, corolla, and androecium, but, occasionally, the calyx 

 remains free from the inner whorls and is free at the base of the in- 

 ferior ovary — Raspalia ( Brunoniaceae ) . The more primitive flowers, 

 with some or all organs spirally arranged, have little fusion among their 

 appendages. The inferior ovary is a characteristic of highly specialized 

 taxa. Anatomy shows clear proof of fusion, especially of adnation. The 

 vascular structure of epipetalous stamens shows all steps in the adna- 

 tion of the stamen to the petal, from that where the two organs are 

 merely appressed to that where all external evidence of fusion is lost 



