40 



GEXERAL BIOLOGY 



and more completely inclosed, and, usually, not 

 felted within: the walls often rise and shape them- 

 selves with marked symmetry and even beauty. The 

 four names given in the table as types of mantle galls are 

 but convenient designations of the more typical forms which 



Fig. 32. Stem, leaf and flower galls, a, a nucleated 

 gall on the twigs of white oak {Quercus alba), b, a 

 mantle gall on the leaves of witch-hazel (Hama- 

 melis virginiana) ; c, simple closed galls on the 

 flowers of goldenrod (Solidago nemoralis). 



often inter-grade or combine together in a single gall. The 

 scroll gall is formed by the uprolling of the leaf margin : 

 the fluted gall, by the furrowing of the blade (chiefly along 

 veins) in elongate grooves. The pocket gall and the cover- 

 ing gall although much alike in appearance are most unlike 

 in fact, being diametrically opposite in their manner of 



