RANALES 427 



families show that different hnes have been followed in the reduction, 

 although some of the placental types are difficult to interpret from 

 descriptions based on herbarium material where the carpels are 

 shrunken. The terms "median," "lateral," "septal," "marginal," "on the 

 external face of the locule" have little certain morphological meaning. 



Typical laminar placentation is present in the Nymphaeaceae and 

 Lardizabalaceae. One modification of this seems to be that of Degeneria 

 and the species of Drimijs that have the decurrent stigmatic crest, 

 where the ovules are borne in two longitudinal bands, about midway in 

 the wings of the lamina. From this type has perhaps been derived the 

 narrower, submarginal rows, characteristic of the follicles of higher 

 orders. Another type of ovule reduction is seen in the Cabombaceae, 

 where the very few surviving ovules are scattered over the locule wall 

 (Fig. 85). 



Modification of the relation of the ovule traces to the vascular system 

 of the sporophyll is of different types within the Ranales. In "all-over" 

 placentation, ovule traces are derived from all parts of the vascular 

 network of laminar veins, including the major veins; the majority of 

 traces depart from anastomoses of the veinlets. With reduction in ovule 

 number, traces from the midvein first drop out. Where there are two 

 longitudinal bands of ovules, the traces of some of the ovules come 

 from anastomoses of branches of both midvein and major lateral veins. 

 With reduction of ovule number in the rows, all the traces arise from 

 strengthened lateral (ventral) bundles — the condition in submarginal 

 placentation, the type characteristic of follicles. In Degeneria and some 

 species of Drimijs, the ovule traces are derived, in part, from anastomo- 

 ses of branches of the dorsal and lateral veins (Fig. 83). In the 

 Cabombaceae, the traces to the few ovules are derived from the net- 

 work of small veins at points remote from the major veins (Fig. 85); 

 this trace origin is evidence of derivation directly from laminar dis- 

 tribution. 



The remarkable two-trace ovule supply in Schisandra and Magnolia 

 is derived from branches of both the midvein and one of the ventral 

 veins. Ovule number in the family has been greatly reduced to one or 

 two, and the large ovule has "captured" two branchlets from the net- 

 work of veins. (In higher orders, solitary basal ovules may have two 

 traces — one from each ventral vein, or even one from adjacent veins of 

 two carpels. ) Placental reduction may be by localization. Trochodendron 

 has numerous ovules but they are restricted "to the distal part of the 

 locule wall." In Exospermum, Pseudowintera, and Belliolum, the fertile 

 area is restricted to an area directly below die stigma. Similarly, in 

 species of Drimijs where the stigmatic ridge is greatly shortened and 

 becomes pseudoterminal, the ovules lie below the stigmatic area. In 



