338 Transactions of the Canadian Institute [vol. ix 



Pontania hyalina Norton. 

 Tannin cells are found abundantly in the epidermis and in the gall 

 tissue generally, except the cells on which the larva is feeding. 



In the normal leaf of S. alba L. on which this gall is found, these 

 cells are not present in the epidermis of the midrib but are plentiful in 

 the wood and bast of the bundle. 



Pontania desmodioides Walsh. 

 Tannin cells are plentiful in the epidermis and in the underlying 

 tissue, but gradually diminish in number in the tissues nearer the larva. 

 This gall also is found on S. humilis Marsh. 



Undescribed gall on petiole of Salix lucida Muhl. 

 Tannin cells are found practically all through the tissues of the gall, 

 but tannin is most plentiful in the epidermis and in the petiole that is 

 involved in the gall swelling. 



Tannin cells are found throughout the normal petiole except in the 

 parenchyma tissue immediately underlying the epidermis. 

 Conclusions concerning Tannin-bearing Tissue, 

 (i) Tannin is more plentiful in gall tissue than in the normal tissue 

 from which it originates. 



(2) In gall tissues it is most abundant in the epidermis and the bast. 



(3) It is more abundant in the older than the younger stages of galls. 



(4) It does not appear to function as food for the larvae as the 

 tannin cells are less abundant in the tissue on which the larvae feed. 



(5) As tannin is always plentiful in the gall epidermis it may serve 

 for protection by rendering the gall tissues unpalatable. 



Technique used in Testing for Tannin. 

 The test substance used was a saturated solution of ammonium 

 chloride saturated with ammonium molybdate. 



Razor sections of the galls were used for testing. 



Notes on Ovipositing by Sawfly Gall Producers. 



Pontania hyalina Norton. 



The^^leaves of Salix alba L, are folded in the bud with the under 

 surfaces towards the outside. The ovipositing takes place before the 

 leaf selected has separated from the others in the same bud. As a conse- 

 quence of this the ovipositor is inserted from the ventral surface of the 

 leaf (Fig. 74). 



May 27th, 191 1. — On this date a producer was observed ovipositing 

 in young leaves, but other leaves on the same stem lower down bore galls 

 that were almost full size. 



June 3rd and 4th. — On these dates producers were seen ovipositing. 



June 1 8th. — Producers ovipositing. 



