THE CARPEL 239 



transitional stages are occasionally seen. In Salix, the ovules are borne 

 low down in a parietal position. Basal placentation derived from 

 parietal seems to be rare, but, in the absence of transitional stages in 

 related taxa or evidence from vascular structure, the derivation of basal 

 placentation may not be evident. 



Where the surviving ovule or ovules are borne on the base at one 

 side of the center or low down on the side wall of the ovary (Fig. 81), 

 they have been called stibbasal or basal, as in free carpels. The ovule 

 of the grasses and that of Ranunculus, for example, are subbasal, as 

 shown by position and by anatomy. 



The nature of the solitary ovule is syncarpous gynoecia has aroused 

 continued discussion. Because of its central position, it has been con- 

 sidered borne on the apex of the receptacle and, therefore, cauline. 

 Evidence from anatomy and ontogeny, with comparisons in related 

 taxa, demonstrates that all these ovules are appendicular. (See "Phyllo- 

 spory and Stachyospory." ) 



Suspended placentation in syncarpous gynoecia occurs where reduc- 

 tion in ovule number in submarginal placentae may leave one or a few 

 ovules surviving at the top of the locule. These ovules may be attached 

 on the ventral wall of the carpels or "on the roof" of the loculus. Often 

 they hang downward on long funicles; this arrangement is similar to 

 that of subbasal, but at the other end of the locule. Anatomv shows 

 that many, perhaps all, of these are surviving members of submarginal 

 placentation. Some suspended ovules are, perhaps, survivors from parie- 

 tal and even laminar placentation. Little is known of the vascular supply 

 of suspended ovules. 



The "gentian type" of placentation (Fig. 80) has sometimes been 

 described as laminar, but laminar placentation, characteristic of only 

 primitive taxa, is not to be expected in so advanced a family as the 

 Gentianaceae. Comparative study of placental form and of carpel 

 anatomy throughout the family shows that ovule arrangement in the 

 gentians is an elaborated and complex form of submarginal. From the 

 evidence of anatomy, the placentae are best interpreted as much en- 

 larged, with flanges sometimes intruding far into the locules and the 

 fertile areas sometimes extended laterally over the inner ovary wall. 

 The placentation of this family, though sometimes closely resembling 

 the primitive laminar type, is a highly specialized type. Relationships of 

 placental type are shown by Fig. 90. 



Reduction in Carpel Number in the Gynoecium. In both apocarpous 

 and syncarpous gynoecia, carpel number has been reduced from an 

 ancestral many to few and to one. Reduced numbers and stages in the 

 reduction are seen in many taxa: in the Ranunculaceae, within the 

 genus Delphinium, three to five in perennial species, one in annuals; in 



