THE CARPEL 197 



formed from such a carpel as this, when indehiscent, is an achene. All 

 stages in the development of the achene type of carpel are present in 

 the Ranunculaceae and Rosaceae. The change is evident, superficially, 

 in the shortening of tlie ovary and the presence of abortive or vestigial 

 ovules. That the achene is a reduced follicle is shown in Fig. 42; the 

 number of traces is reduced by loss and by fusion, and traces to lost 

 ovules persist in the ovary wall. Clematis, Caltha, Calycanthus, and 

 Adonis also show derivation of the achene from the follicle. 



Reduction and simplification of the carpel have occurred independ- 

 ently in many families and apparently from follicular types that were 

 at various stages of specialization: from those with well-developed 

 style- — the style retained — as well as from those with sessile stigma; 

 from stipitate carpels — the stipe retained — and from sessile carpels. Re- 

 duction may proceed beyond functional form, with the last ovule lost 

 and the locule nearly or quite closed — the "solid" carpel. 



The SoLm Carpel 



The term solid, as applied to carpels, became prominent in the 1920s 

 and 1930s when the theory of carpel polymorphism aroused consider- 

 able discussion. But the term was used in the older literature, much 

 more soundly, for sterile carpels with locule greatly reduced or absent 

 (Fig. 76), carpels that are vestigial or abortive. In its early use, the 

 term was descriptive, and its nature, a reduction form, correctly in- 

 terpreted. Sterile carpels are frequent in many taxa and show all stages 

 in structural reduction — compressed and "consolidated" in various ways 

 and degrees; rodlike, free or adnate to normal carpels; short stubs. In 

 syncarpous gynoecia, they may be represented by vascular supplies 

 only. Vestigial carpels are most readily recognized in staminate flowers 

 of monoecious and dioecious genera. In some unisexual flowers that 

 have no external remnants of reduced carpels, stubs of the carpel traces 

 are present in the receptacle. In syncarpous taxa that show series in 

 gynoecial reduction, solid carpels are often apparent as remnant struc- 

 tures. Triglochin has obvious solid carpels; within the genus, carpel 

 number is reduced from six to three; species with three normal carpels 

 have three sterile carpels, with little or no locule (Fig. 76F). (The 

 solid carpel as a reduction form is discussed further under Syncarpy. ) 



The Stigma and Transmitting Tissue 



In the more primitive carpels, the stigma is not clearly set apart: it 

 merges into the style or ovary; in more specialized forms, it is usually 

 distinct. In such genera as Degeneria and Drimijs, it is represented by 

 the stigmatic crest, consisting of proliferated and papillose marginal 

 bands extending the full length of the lamina (Fig. 72C). These bands 



