THE CARPEL 215 



The primitive carpel has numerous ovules distributed over the adaxial 

 surface, except perhaps for a narrow marginal band. Ovules are occa- 

 sionally borne even on the midvein area, though less abundantly than 

 elsewhere. There seems to be no definite pattern of position or of origin 

 of vascular supply. Each ovule is supplied by a slender trace, derived 

 largely from the meshwork of small bundles of the lamina; the traces 

 represent the tips of more or less free veinlets, or shorter strands derived 

 at points of anastomosis in the meshwork and involving small veins 

 only, or small and larger veins, even the midrib. With reduction in 

 number, the ovules are first restricted to rows near the margins, with 

 their traces derived from ventral veins — submarginal placentation. The 

 rows are at first rather broad and loose, with traces of some of the 

 ovules derived from the lamina meshwork {Degeneria, Drimijs; Fig. 

 83D); with further reduction, the rows become linear, with all traces 

 from the ventral veins; further reduction of ovules in the submarginal 

 lines leaves few, and ultimately two or one. The persisting ovules are 

 commonly the proximal members of the row — often with vestigial, distal 

 ovules above. Persisting distal ovules — two or one — are uncommon or 

 rare ( Proteaceae ) , and median ovules are rare. "Basal," "suspended," 

 and "median" solitary ovules, especially those of syncarpous ovaries, 

 represent various morphological situations and require individual in- 

 terpretations (Figs. 81 and 82). Solitary ovules may have more than 

 one trace, and the traces mav come from the two ventral bundles or 

 even, very rarely, in syncarpous ovaries, from the ventrals of different 

 carpels. Fusion of the major carpellary veins — characteristic of many 

 achenes (Fig. 42) — may suggest the derivation of ovule traces directly 

 from the dorsal vein. 



The Nymphaeaceae and Cabombaceae provide excellent examples 

 of reduction to few, two, and one ovule directly from lamina distribu- 

 tion. The vascular structure of the carpels shows that, in reduction in 

 ovule number, intermediate submarginal stages have been omitted. Most 

 of the genera in the Nymphaeaceae have the numerous ovules scattered 

 widely over the carpel surface; Neltimbo has only one; in the Cabomba- 

 ceae, there are three (rarely four); and in Brasenia, two (rarely three) 

 (Fig. 85). Ovular position in these genera has long been a morphologi- 

 cal puzzle, but their positions on the carpel walls and the derivation of 

 their traces show that they represent scattered members of ancestral 

 laminar distribution. 



In taxonomic treatments, ovule position in these taxa has been 

 described as "parietal" and "on the sides of the carpel" — more speci- 

 fically, in Cahomha, "on the lateral walls" and, in Brasenia, "along the 

 dorsal suture"; these locations are also called by the morphologically 

 better terms "laminar lateral" and "laminar dorsal," respectively. In 



