406 MORPHOLOGY OF THE ANGIOSPERMS 



advanced characters for a ranalian family, but the leaf node, with two 

 traces from one gap, is primitive. 



The family is characterized by a cortical vascular system of inverted 

 strands, which supplies the ventral traces of the leaves. This system ex- 

 tends into the flower, but its relations with the traces of the floral 

 appendages are not uniform. The lower tepals receive all their supplies 

 from the cortical system; all the upper organs receive their supplies 

 from the stelar system. The cortical bundles of the stem are inverted; 

 those of the flower, normally oriented. 



The morphology of the cortical vascular system in angiosperms is 

 obscure. Magnolia has a strong, uniform cortical system in the flower; 

 Asimina has a partial system, not uniform throughout the flower. Both 

 these genera lack cortical bundles in the stem. Calycanthus, which has 

 a weak cortical system in the flower, has a strong system in the stem. 

 The cortical system of Calycanthus is unlike that of Magnolia and 

 Asimina, and the two types are, or seem to be, unrelated. In Calycan- 

 thus, the peduncle, like the stem, contains a cortical system of vascular 

 bundles, ending at a low level in the flower; the cortical bundles divide 

 and all enter the lowest tepals — three or four traces to each tepal. The 

 axial system, continuing upward, forms more bundles by radial division, 

 some of which supply the upper tepals; others continue to the stamens 

 — one trace each — on the inner rim of the hollowed receptacle; still 

 others, becoming inverted, turn downward into the hollow of the re- 

 ceptacle wall. These inner inverted bundles may lie close to, and even 

 fuse with, the "lower," outer, normally oriented bundles. Traces to the 

 carpels — three each — are given off, in the usual manner, toward the 

 inside by the descending strands, and the continuing strands form a 

 weak meshwork beneath the floor of tlie hollow receptacle. The course 

 of the vascular bundles — upward and downward and across the apex 

 of the receptacle — explains the presence of inverted and concentric 

 bundles and the "terminal" network of vascular tissue in the receptacle, 

 and shows clearly the nature of the receptacle tip — an inverted apex. 

 The passage of traces inward to some of the stamens and to the carpels 

 is obviously normal. 



The presence of cortical bundles in these primitive taxa has led to 

 the opinion that cortical vascular systems are probably primitive for 

 angiosperms. But this conclusion seems unjustified, because of differences 

 in structure in the taxa, and because a somewhat similar system is 

 present in the Melastomaceae, Myrtaceae, and Acanthaceae (Justicia). 

 Cortical systems may represent vestiges of the ancestral structure of 

 complex fern steles, but seem rather to represent specializations. 



The primitive characters of this family are the numerous, free, spiral 

 tepals, stamens, and carpels; lack of distinction of calyx and corolla; 



