THE CARPEL 229 



and, in contrast with closure in the condupHcate carpel, the dorsal sur- 

 faces meet and fuse. In some taxa, the marginal strips of the lamina are 

 deeply inrolled and recurved, so that the placentae are turned laterally 

 or even inverted (Fig. 74). 



The problem of methods of the phylogenetic closure of the carpel 

 needs critical study; is there only one basic method, by upfolding, or is 

 there another, by inrolling? There is strong evidence that the con- 

 duplicate carpel represents only one type. In leaf vernation, there are 

 several types of folding, including involute and conduplicate types; 

 under xerophytic conditions, involute leaves are common. If involute 

 types have been derived from conduplicate, the change in areas of con- 

 tact from the ventral to the dorsal surface is a major step. The position 

 and orientation of the ventral (submarginal) bundles in relation to the 

 areas of union in closing is important in determining whether involute 

 closure has been derived from conduplicate or is of independent origin. 

 These bundles point out placental position in submarginal placentation 

 and the extent of insertion of marginal bands of the lamina witliin the 

 closed carpel. The derivation of carpel type with broad bands of lamina 

 enclosed within the carpel from the conduplicate carpel requires elabo- 

 rate evolutionary modification: the opening up of a conduplicate carpel 

 with appressed ventral surfaces, followed by an inrolling of marginal 

 sti'ips, with union of dorsal surfaces. The involute carpel is, in all 

 probability, an independent type. Closing of the carpel has doubtless 

 come about independently several or many times, as have advances in 

 other characters; it is still in process in many living taxa. It would be 

 strange if all closures were structurally alike, especially in the light of 

 the variety of folding and rolling of leaves in buds and cotyledons in 

 the seed. 



In all studies of carpel structure and floral anatomy, it is important 

 that the carpel be recognized as an immature organ at flowering time 

 and should not be compared with fully developed stamen or petal. The 

 vascular tissues, especially the connections of the traces of the carpel 

 to the vascular receptacular stele, are frequently immature at flowering 

 time; the downward extension of the traces may be incomplete. In the 

 Capparidaceae-Cruciferae line, this late development is marked; connec- 

 tions are not completed until the fruit is partly developed. Interpreta- 

 tions of the gynoecia of these taxa based on the statement that the 

 carpellary traces end blindly in the pith have no value. 



The advanced carpel is congenitally closed; it arises from a ring- 

 shaped primordium as a tubular organ. The carpels of many taxa are 

 closed in part ontogenetically and in part congenitally; in early on- 

 togeny, the primordium is crescent-shaped; later, it becomes ring-shaped. 

 Failure to recognize the existence of this combination of types of 



