450 HABITATIONS OF INSECTS. 



of all sizes from that of a pin's head to that of a walnut. 

 Nor is their situation on the plant less diversified. Some 

 are found upon the leaf itself; others upon the footstalks 

 only; others upon the roots ; and others upon the buds a . 

 Some of them cause the branches upon which they grow 

 to shoot out into such singular forms, that the plants pro- 

 ducing them were esteemed by the old botanists distinct 

 species. Of this kind is the Rose-willow, which old Ge- 

 rard figures and describes as " not only making a gallant 

 shew, but also yeelding a most cooling aire in the heat 

 of summer, being set up in houses for the decking of the 

 same." This willow is nothing more than one of the 

 common species, whose twigs, in consequence of the de- 

 position of the egg of a Cynips in their summits, there 

 shoot out into numerous leaves totally different in shape 

 from the other leaves of the tree, and arranged not much 

 unlike those composing the flower of a rose, adhering to 

 the stem even after the others fall off. Sir James Smith 

 mentions a similar lusus on the Provence willows, which 

 at first he took for a tufted lichen b . From the same 

 cause the twigs of the common wild rose often shoot out 

 into a beautiful tuft of numerous reddish moss-like fibres 

 wholly dissimilar from the leaves of the plant, deemed 

 by the old naturalists a very valuable medical substance, 

 to which they erroneously gave the name of Bedeguar. 

 None of these variations is accidental or common to se- 

 veral of the tribe, but each peculiar to the galls formed 

 by a single and distinct species of Cynips. 



How the mere insertion of an egg into the substance 

 of a leaf or twig, even if accompanied, as some imagine, 

 ;i Reaum. iii. 417 &c. h Introd. to Botany, 349. 



