THE PLANT BODY 



27 



of taxa of widely scattered families — Ericaceae (Clethra, Pyrola, 

 Epigaea), Caryophyllaceae (Anagallis). In some free carpels, the 

 stigmas are two-lobed and the vascular supply forked. The double- 

 bundle was described in many taxa in demonstration of the carpel 

 polymorphism theory. 



Two-ti-ace stamens are uncommon but are present in both advanced 

 and primitive taxa: Austrohaileija, Sarcandra, Victoria, NupJiar, 

 Casuarina, Cijrtandra, Eranthe- 

 mum, Donjanthes (two pairs), 

 several genera in the Betulaceae, 

 Fagaceae, and Proteaceae. Origin 

 of the single trace in stamens is 

 seen in Hakea, where, in a single 

 species, even a single Hower, some 

 stamens have two independent 

 traces and others have obviously 

 double traces, which may fork 

 distally. 



Sporophylls with double vascular 

 supplies have doubtless not been 

 recorded because they were con- 

 sidered abnormal. The frequency 

 of occurrence of these sporophylls 

 with two traces cannot be com- 

 pared with that of similar leaves, 

 because trace origins in the flower 

 are often concealed by fusion. 



The presence of two traces in 

 cotyledons has long been known 

 and at one time aroused interest 

 as possible evidence of ancestral 

 dichotomy persisting in the em- 

 bryo. This formed part of the 

 basis for a "theory of the double 



leaf trace"— a theory that two-trace appendages characterize most major 

 vascular taxa. This theory received little attention, because of interest 

 in the problem of the phylogenetic relation of the cotyledons of the 

 dicotyledons and the monocotyledons— does the single cotyledon of 

 the monocotyledons, with two traces, represent two fused cotyledons, 

 or one of a pair, the other lost (Chap. 9)? The two-trace cotyledon 

 was considered primitive for the Liliaceae, but from the viewpoint that 

 it represents retention of the vascular supply of the two cotyledons of 

 dicotyledonous ancestors, rather than as basic angiosperm structure. 



B 



Fig. 8. Diagrams of cotyledonary nodes 

 and cotyledon. A, B, of Degeneria viti- 

 ensis showing four traces in petiole and 

 venation in A and a trilacunar node 

 with three cotyledons with four traces 

 each from three gaps each; C, of Mag- 

 nolia grandiflora showing a trilacunar 

 node with two cotyledons with four 

 traces each. The four lateral traces "de- 

 rived by the bifurcation of two traces 

 which arise from two gaps in the stele." 

 {After Swamy.) 



