332 IXSECT ARCHITECTURE. 



bably from this circumstance than from the red colour of 

 its twigs. The older botanists, not being aware of the 

 cause of such excrescences, considered the plants so affected 

 as distinct species; and old Gerard, accordingly, figures 

 and describes the rose- willow as " not only making a gallant 

 show, but also yielding a most cooling air 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 ( Cijnips solids) 

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

 the bedeguar and the oak artichoke, causing leaves to spring 

 out, of a shape totally different from the other leaves of the 

 tree, and arranged very much like the petals of a rose. 

 Decandolle says it is found chiefly on the Salix helix, S. alha-> 

 and S. Riparia* 



A production very like that of the rose- willow may be 

 commonly met with on the 3"oung shoots of the hawthorn, 

 the growth of the shoot affected being stopped, and a 

 crowded bunch of leaves formed at the termination. These 

 leaves, beside being smaller than natural, are studded with 

 short bristly prickles, from the sap (we may suppose) of 

 the hawthorn being prevented from rising into a fresh shoot, 

 and thrown out of its usual course in the formation of the 

 arms. These bristles appear indiscriminately on both sides 

 of the leaves, some of which are bent inwards, while others 

 diverge in their natural manner. 



This is not caused by the egg or grub of a true gall-fly, 

 but by the small white tapering grub of some dipterous 

 insect, of which we have not ascertained the species, but 

 which is, probably, a cecidomyia. Each terminal shoot is in- 

 habited by a number of these — not lodged in cells, however, 

 but buiTowing indiscriminately among the half-withered 

 brown leaves which occupy the centre of the production. 

 (J. E.) 



A more remarkable species of gall than any of the above 

 we discovered, in June 1829, on the twig of an oak in the 

 grounds of Mr. Perkins, at Lee, in Kent. AYhen we first 



* Flore Fran9. Disc. Preliminaire. 



