206 



MORPHOLOGY OF THE ANGIOSPERMS 



partly cauline in nature — have greatly complicated the terminology of 

 placentation. Morphological consistency requires interpretation of placen- 

 tation in the simple, free carpel as the basis for that in the fused-carpel 

 ovary. 



The follicle type of carpel, with the carpellary margins approximated 

 or united, is generally accepted as primitive. In this carpel, there are 

 two types of placentation. Commonly, the ovules are borne in rows near 



B 



Fig. 81. Diagrams showing subbasal placentation. A, B, Scirpus robustus, showing 

 reduction from free central (one lateral ovule surviving on original central column); 

 C, D, Saccharum and Bromus showing reduction from submarginal placentation: 

 Saccharum in longitudinal section of ovary showing vascular supply to ovule, 

 Bromus in cross section of ovary at level of ovule attachment showing three carpels 

 (one fertile), three dorsal and three (double) ventral bundles, the ovule supplied 

 by the large ventral; E, diagram of typical vascular supply for flower in Cyperaceae; 

 F, series of cross sections of flower of Cijpcrus dcntatus showing origin and path 

 of traces to carpels and stamens: three carpels, each with dorsal and two ventral 

 traces, the pairs of ventrals uniting in a central column, which supplies the ovule 

 traces. ( A, B, E, F, after Blaser. ) 



the margins — submarginal placentation; infrequently, they are dis- 

 tributed broadly over the lamina — luminar placentation (also termed 

 diffuse, scattered, superficial, reticulate ) . Laminar seems morphologically 

 preferable. Reduction in ovule number in the carpel with submarginal 

 placentation, together with modification of carpel size and form, brings 

 about changes in apparent ovule position; the one, two, or few surviving 

 ovules are usually borne near the base or apex of the locule, and the 

 placentation is termed basal (Fig. 81) and suspended (apical) (Fig. 

 82), respectively. Basal placentation, derived directly from laminar 



