THE PLANT BODY 



29 



There is strong correlation between the simple, pinnate leaf and the 

 unilacunar node, but there are also extreme exceptions, as in Eupomatia, 

 where there are 7 to 11 traces from as many gaps. Leaves with sheath- 

 ing bases usually have several traces and gaps. Though the fundamental 



; 



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*; 



Fig. 9. Two series of diagrams showing vascularization of node and successively 

 hio-her levels of the petiole of Dcgeneria viticnsi^: series 1 from a seedling leaf 

 and series 2 from a mature leaf. {After Swamy.) 



vascular relationship of node and leaf now seems clear, variations re- 

 lated in part to leaf form are many. For example, highly complex nodal 

 structure accompanies interpetiolar stipules and other stipules of un- 

 usual form and function. 



Pinnate venation may have been derived in two ways: directly from 

 a simple, two-trace leaf with a double midvein, by a strengthening of 

 lateral veinlets; from a three-trace leaf with three veins by a weakening 



