191 a] Morphology and Biology of Insect Galls 387 



Fig. 84. Undescribed gall on the leaf of Salix lucida Muhl. Section 

 of a well-grown gall on the leaf petiole. The two arms of the 

 bundle are shown widely separated by proliferation set up 

 in the pith. The arrangement of the cells of the gall tissue 

 in curved rows is shown and the presence of elongated air 

 spaces between these. X15. 



Fig. 85. Undescribed gall on the leaf petiole of Salix humilis Marsh. 

 Section showing the ovipositor wound. Around the edge 

 of the incision is shown the cambium tissue from which the 

 greater part of the gall tissue has been produced. X 18. 



