404 MORPHOLOGY OF THE ANGIOSPERMS 



tionary advance in angiosperms, based on statistical correlations, lists 

 the Myristicaceae as the third most primitive family, but, in this treat- 

 ment, unisexuality is considered primitive. 



SCHISANDRACEAE 



Two genera of woody vines, Schisondra and Kadsura, each with over 

 twenty species, constitute the Schisandraceae. On the basis of certain 

 advanced characters, the genera have been removed from the Magnolia- 

 ceae (sensu lato) and considered to form an independent family. 



The family has a combination of primitive and relatively advanced 

 characters. Among primitive characters are the polymerous perianth 

 (without distinction of calyx and corolla); many stamens and carpels, 

 spirally arranged on an elongate receptacle; carpels not completely 

 closed, with divided, decurrent stigmas; phloem without fibers and with 

 long, slender, overlapping sieve elements, which have many sieve areas; 

 vessels scalariform, with numerous narrow perforations and scalariform 

 side-wall pitting. Advanced characters are the unisexual flowers; the 

 tricolpate pollen; the unilacunar node with tliree traces; xylem ranging 

 from relatively primitive to highly specialized; ovules reduced to from 

 two to five. (Highly specialized xylem is associated with the vine 

 habit. ) 



The carpels resemble those of the Magnoliaceae in reduction of 

 ovules and in. the complex ovular supply, but the origin of the ovular 

 traces is clearer in the Schisandraceae than in the Magnoliaceae, because 

 of the absence of a cortical vascular system. The placentation of this 

 family, like that of the Magnoliaceae and Illiciaceae, is reduced laminar. 

 The ovule supply is derived from either the dorsal or ventral bundles 

 and may be double, with a trace from both dorsal and ventral bundles. 

 This ovule supply indicates, as an ancestral ovular supply, a vascular 

 meshwork, which supplies individual ovules from all parts of the 

 vascular skeleton of the lamina. (Double ovule traces represent anoma- 

 lous vascular morphology that results from placental reduction, where, 

 as an ovule is lost, its vascular supply may be "captured" by an adjacent 

 surviving ovule. This condition is occasional in basal ovules in syn- 

 carpous ovaries, where it is derived by reduction from submarginal 

 placentation. ) Reduction of ovule number to two or one, directly from 

 laminar placentation is probably rare; this reduction is demonstrated 

 by vascular structure of the carpel in these three families and in the 

 Nymphaeaceae and Cabombaceae (Fig. 85). 



The Schisandraceae, together with the Illiciaceae, seem to be related 

 to the Magnoliaceae (sensu stricto) and to have been derived from 

 the same ancestral stock, but are more specialized families than the 

 Magnoliaceae. 



