V] PINNATE-RETICULATE VENATION 59 



In a fourth case, appropriately termed pinnate-arcuate 

 venation, the single midrib gives off secondaries, which 

 start in pinnate order, but curve forwards towards the 

 apex of the leaf and there suddenly disappear in the 

 network, without forming distinct loops or reaching the 

 margins. The secondaries are typically much stronger 

 than the tertiaries, and are few and distant. 



The following are examples of pinnate-arcuate vena- 

 tion : 



Buckthorn Dogwood. 



In the following cases, which we may term pinnate- 

 reticulate venation, the single midrib gives off pinnate 

 secondaries at various angles and distances, but these 

 soon break up into the general network, long before 

 reaching the margin, and without forming distinct loops 

 e.g. Crack Willow (Fig. 19), and the following: 



Elder Ash Traveller's Joy 



Robinia Willows Honeysuckles 



Lilac Privet Holly 



Apple Blackthorn Bullace 



Plum Gean Cherry 



Almond Bird Cherry Mezereon 



Pear Arbutus Bittersweet. 



In the following (Fig. 20), the venation is reticulate, 

 breaking up so rapidly that although traces of its reference 

 to the pinnate or palmate type exist, such type is not 

 prominent : 



Barberry Poplars Mahonia 



Daphne Mulberry Bittersweet 



Pear Lycium Cotoneaster 



Arbutus Apple Vaccinium Myrtillus 



Lilac Salix reticulata, 



