v] 



PALMATE-PINNATE VENATION 



65 



come to examine the behaviour of the secondaries, thrown 

 off from the various primary ribs. 



In the one, we find three or more primary ribs enter 

 the margin from the petiole, of which the central one 

 runs forward to the apex as the midrib and ends in the 

 tip, while the lateral primaries radiate in diverging lines, 

 running to the tips of the lobes and acting, so to speak, 

 as subsidiary midribs, one to each lobe. Each of these 

 primaries gives off secondaries in pinnate order, which in 

 their turn run to the margins, and either end there, or 

 loop, or break up in different cases ; e.g. Viburnum Opulus 

 (Fig. 23). This form may be termed palmate-pinnate. 



Fig. 24. Leaf of Ivy, Hedera Helix, showiDg palmate-reticulate 

 venation. A midrib ; B and C lateral and basal primaries ; D arid E 

 network of secondaries, tertiaries, &c. (Ett). 



In the other case, the radiating primary ribs diverge 



w. ii. 



