226 MORPHOLOGY OF THE ANGIOSPERMS 



carpel length is greatly reduced and ovule number is reduced to one. 

 The cross zone on which the solitary ovule is borne is considered 

 "latent," a supposedly primitive stage in the development of the peltate 

 carpel; it is, rather, a vestigial condition. The "unifacial" character of 

 the carpel is considered important evidence of the peltate nature of the 

 carpel, and the presence of a unifacial "stalk" (stipe) is considered 

 further proof of peltate form; the stalk "must have been formed by a 

 cross zone." But the stipitate carpel is characteristic of many primitive 

 taxa — some of the woody Ranales, Ranunculaceae, Rosaceae, Helobiales 

 — and is clearly a basic feature of the primitive carpel, rather than an 

 advanced character. The unifacial form of the carpel and the stipe is 

 not evidence that the carpel is basically a peltate organ. Simple folding 

 or inrolling of the carpel forms a unifacial structure. Anatomy supports 

 the involute, not the peltate theory, of carpel nature by the presence of 

 the strong dorsal bundle and the pair of smaller, inverted ventral 

 bundles on the side opposite the dorsal. Support for the peltate theory 

 is seen in the arrangement of the bundles — "in a cylinder" — but size, 

 number, and arrangement are those of a folded, bifacial organ. "In a 

 cylinder" is morphologically an incomplete description. 



The peltate theory must explain the presence of the prominent ventral 

 suture of the carpel which, under this theory, is built up by a simple 

 transverse (cross-zone) meristem. The explanation given is that the 

 suture is the result of earlier and stronger growth on the dorsal side. 

 But this does not explain the double epidermal layers connecting dorsal 

 and ventral epidermises, which are present in many carpels. The typical 

 mature carpel is, of course, ascidiform, in that it is tubular, but this 

 form is attained, morphologically, by simple folding or inrolling and 

 fusion, not by the complicated process of union of basal lobes and 

 development of a new "meristem." 



The peltate theory has been extended far beyond its original basis; it 

 has been applied also to stamens, petals, and cotyledons. The course of 

 development and the elaboration of the theory parallels that of the 

 theory of carpel polymorphism. From an unsound base, the theory has 

 been extended broadly to other floral organs, with a consequent amaz- 

 ing entanglement of superfluous interpretations. Like the polymorphism 

 theory, it is unsound in basis and in detail. 



The Solitary Carpel. Gynoecia that appear to consist of a single carpel 

 are of two types: those that are, morphologically, single carpels and 

 those that consist of more than one carpel but resemble a single carpel 

 and are well described as "pseudomonomerous." The single carpel is a 

 surviving member of a multicarpellate gynoecium, as shown by com- 

 parative studies in several families, especially the Ranunculaceae, and 

 from the evidence of vascular anatomy, which shows vestigial vascular 



