380 INSECT ARCHITECTURE. 



have several of these galls, which are of various sizes 

 from that of a filbert to that of a walnut. 



Leafy Gall of Dyers-Broom, produced by Cynips genittx t 

 A, gall, natural size ; B, a leafet magnified. 



A similar hut still more beautiful production is 

 found upon one of the commonest of our indigenous 

 willows (Salix purpurea), which takes the name of 

 rose-willoiv, more probably from the circumstance 

 than from the red colour of its twigs. The older 

 botanists, not being aware of the cause of such ex- 

 crescences, considered the plants so effected as dis- 

 tinct species; and old Gerard, accordingly, figures 

 and describes the rose-willow as " not onlie making 

 a gallant shew, but also yeelding a most cooling aire 

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

 decking the same." The production in question, 

 however, is nothing more than the effect produced 

 by a species of gall-fly (Cynips salicis) depositing its 

 eggs in the terminal shoot of a twig, and, like the 



