47° 



Saw-riies, Call-Hies, Ichneumons, 



position, and the interesting response or reaction of the plant to the growth- 

 stimulating irritation of the gall-fly larva are subjects which have attracted 

 much attention and study, but concerning which much remains to be dis- 

 covered. In size and shape the galls present amazing variety; some are irreg- 

 ular little swellings on the leaves, others are like small trumpets, others like 



rosettes or star-like with radiating 



points; on the twigs some are spherical, 



some elongate, and some large and 



reniform. Figs. 657 to 665 show 



something of 



this variety. 



In their interior 



make-up they 



also differ 



much ; some 



have a large 



hollow central 



space ; some 



Fig. 659. 

 Fig. 658. — Galls on leaf of California white oak. (Natural 



size.) 

 Fig. 659. — Trumpet-galls on leaves of California white oak. 



(Natural size.) 



are filled with open, syxmgy tissue, and some are 



solid except for the cells and tunnels of the larvic. 



In some but a single larva lives; in others arc three 



or four or a dozen. E.xternally some are smooth, 



some roughened, some hairy. They occur on leaves, 



branches, and roots in both oak and ro.se. Only Fig. 660.— Galls on leaf 



a few Cynipid galls are known on other plants "f California white oak. 



. . (Natural size.) 



than these. In the face of the host of species of Lyni- 



pida; found in this country — over 200 gall-making kinds are known, besides 

 a score of parasitic species — and their small size and generally similar appear- 

 ance, we shall not undertake to describe any of the various species. Corn- 

 stock describes in his Manual several of the more common eastern galls, or 



