58 



PINNATE-ARCUATE VENATION 



[CH. 



aries, which do not end in the margin, but take a sinuous 

 or curved, or more rarely straight, course, and then bend 

 forwards at their tips and join in a loop, convex to the 

 margin, with the next upward secondary (Fig. 17). We 

 may term this pinnate-looped venation. 



The following afford examples of pinnate-looped vena- 

 tion : 



Walnut 

 Robinia 

 Spindle Tree 

 Apple 

 Honeysuckle. 



Traveller's Joy Ailanthus 



Rose Sweet-briar 



Lilac Holly 



Blackthorn Alder Buckthorn 



Fig. 18. Leaf of Buckthorn, Rhamnus Catharticus, showing piunate- 

 arcuate venation. The few pinnate secondary ribs curve forward and 

 lose themselves in the reticulum near the apex (D). 



