THE AXGIOSPERMAE 



1 1 17 



ring, near the base of the receptacle. From this are given off the sepal traces, 

 normally three to each sepal, leaving gaps in the ring, which break it again 

 into a hollow cylinder of separate bundles (Fig. 109 1). Petals and stamens 

 are alike in normallv receiving one trace only. At each point where a trace 

 is given off one of the axial strands divides radially, either into two or three. 

 If into two, one portion becomes the trace and the other remains in the 

 axial cylinder. If there is division into three, then the median portion 

 becomes the trace and two axial strands remain. Such increases in the 

 number of axial strands are counter- 

 balanced by frequent fusions between 

 adjacent strands, so that the whole axial 

 cylinder is like a network of vascular 

 bundles. 



The carpels most generally receive 

 three traces (Fig. 1092), though': the 

 number varies from one to five. The 

 strong dorsal trace arises first, that is 

 to say lowermost, then the two axial 

 strands, lying on each side of the gap 

 left by the dorsal trace, divide, and the 

 portions lying next to the gap become 

 the ventral or marginal traces of the 

 carpel. 



The receptacle anatomy is thus not 

 fundamentally different from that of a 

 vegetative stem w^hich has limited growth ^^^ 

 and crowded appendages, though it is 

 evident that the appendages in the flower 

 are not of uniform nature. Were we to 

 judge by vascular anatomy, as many 



believe that we may, the floral axis would be regarded as clearly homologous 

 with a vegetative axis. 



Eames, who maintains this view, has endeavoured to typify floral 

 vascular structures by reference to two main patterns: 



1092. — Diagrams showing the 

 similarity of the typical 3-trace 

 supply to the foliage leaf, A, and to 

 the carpel, B. (After Eames, partly 

 modified from Sinnott and Bailey.) 



I. 



The Aquilegia Type (Fig. 1093). 3-trace sepals, i -trace petals, 



■ I -trace stamens, 3-trace carpels. Between the last of the stamens 



and the first of the carpels the stele unites into a ring. Remnants 



of the axial cylinder may persist for a short distance above the 



carpels, mostly in the form of phloem and rapidly fading out. 



The Scheiichzeria Type (Fig. 1094). i -trace perianth members, all 

 similar, i -trace stamens. The vascular ring then re-unites and 

 subsequently breaks to give off the dorsal traces to the carpels. 

 The bundles left in the ring divide to form the six ventral traces 

 of the carpels, two to each. Above the carpellar)^ level there is no 

 trace of vasculation remaining. 



