BLACKTHORN 



193 



twigs, are forms passing into the less spinose varieties of 

 P. spinosa. They present difficulties owing to their 



Fig. 96. Blackthorn, Primus spinosa, p. 192 (D and Sc). 



resemblances to Rhamnus, but the buds and leaf-scars in 



the latter are sub-opposite or opposite (see pp. 159, 160). 



w. i. 13 



