386 Transactions of the Canadian Institute. [vol. ix 



Fig. 75. Pontania hyalina Norton on the leaf of Salix alba L. Section 

 of a more mature stage than numbers 73 and 74. The amount 

 of gall tissue derived from the various sources can no longer 

 be distinguished. The uniformity of the tissue is very marked. 



X25. 



Fig. 76. Pontania pomum Walsh of the leaf of Salix cordata Muhl. Sec- 

 tion through an early developmental stage in which the larva 

 had not freed itself from the egg membrane. There is shown 

 the laceration of the bundle of the midrib by the ovipositor and 

 the proliferation in the various tissues of the leaf. X20. 



Fig. 77. Pontania pomum Walsh on Salix cordata Muhl. Section of a 

 nearly full-grown gall, showing the distribution of the aeri- 

 ferous tissue and the location of the vascular strands. Xl8. 



Fig. 78. Pontania (N.S.) on the leaf of Salix humilis Marsh. Section 

 at right angles to the midrib of the leaf to which the gall is 

 attached. The general character of the gall tissue is shown and 

 the distribution of the vascular strands from the wounded 

 bundle. X20. 



Fig. 79. Pontania (N.S.) on the leaf of Salix humilis Marsh. Section 

 through the midrib from which two galls had originated. The 

 bundle is shown completely severed. X8. 



Plate XIII. 



Fig. 80. Pontania desmodioides Walsh on the leaf of Salix humilis Marsh. 

 Section through a chamber containing an unhatched larva. 

 Proliferation is well marked in all the tissues of the leaf. X40. 



Fig. 81. Pontania pisum Walsh on the leaf of Salix discolor Muhl. 

 Section of a mature gall, showing the general character of the 

 tissues. The dark band at the upper right of the figure marks 

 the line of attachment of the gall to the blade of the leaf. Just 

 beneath this line the proliferation in the palisade parenchyma 

 is shown. .X20. 



Fig. 82. Undescribed gall on the leaf of Salix lucida Muhl. Section of 

 a young gall on the midrib, showing the commencement of the 

 proliferation in the pith of the bundle. X20. 



Fig. 83. Normal leaf of S. lucida Muhl. Section through midrib for 

 comparison with the preceding. X25. 



