240 



MORPHOLOGY OF THE ANGIOSPERMS 



Cimiciftiga, several to one; and one in the closely related Actaca. In 

 the Rosaceae, reduction has been from many to one in Sanguisorba, to 

 one in the Prunoideae, where one or two abortive carpels frequently 

 develop. In the Proteaceae, the solitary carpel is the survivor of two; 

 one is lost in ontogeny, as seen in MangUetia. 



Syncarpous gynoecia, with carpels reduced to one, have been well 

 termed pseudonionomerous. These gynoecia may show external evi- 

 dence of their compound nature in the form of the ovary, the number 

 of styles or stigmas, or the presence of abortive carpels adnate to the 

 fertile one. Other evidence is in internal structure of the ovary and re- 

 ceptacle and in the gynoecia of related taxa. All available evidence 



Suspended 



Basa 



Suspended 



Parietal 



Submarginal 



Laminar 



"Lateral" 

 ■'Median" 

 "Dorsol" 



Fig. 90. Chart showing phylogenetic relationships of placentation types based on 

 evidence from comparative form, ontogeny, and vascular anatomy. 



must be used, because reduction may have gone very far, even to com- 

 plete external loss of the component carpels. Ontogeny and the vascular 

 skeleton will usually add to the evidence from superficial form and re- 

 lated taxa. Reduction in ovule number accompanies tliat in carpel num- 

 ber, and this type of gynoecium usually has a single ovule. Some 

 pseudomonomerous carpels have been described as achenes, which 

 they may resemble in form and ovule number. Pseudomonomerous 

 carpels are found throughout the angiosperms — in many genera of the 

 Urticales, in Sparganium, Phnjma, Rhus, Dipsacus, Viscum, Smilax, 

 Ceratophyllum, Nandina, Ficus, Pontederia, Cassijtha, the Gramineae, 

 Valeriana, Viburnum, Lindera, many palms. In taxonomic treatments, 

 some of these taxa are described incorrectly, on the basis of external 

 structure, as having one carpel; others, such as Ulnms, are correctly 

 described as having two or, as in the grasses, three. The structural 

 form of these reduced syncarpous gynoecia shows great variety. The 



