S8 



NEW YORK STATE MUSEUM 



Fig. 10 English 

 elm pouch gall (nat- 

 ural size, original) 



green, appearing almost as if varnished and 

 decidedly paler than the leaf, and as they age, 

 assume variable purplish tints. The entrance to 

 the gall is on the under side of the leaf and 

 is guarded by pale, fuzzy hairs. Three or four 

 galls frequently occur on a leaf, though ^liss 

 Patch has recorded as many as thirty-six. The 

 interior of the gall is slightly ridged and in- 

 habited by numerous plant lice. Technical de- 

 scriptions of this species are given by Miss 

 Patch (Me. Agric. Exp't Sta. Bui. i8i, p. 216- 

 19, 1910) to which the reader is referred for 

 further details. This species presumably has 

 a wide American distribution and can be con- 

 trolled, if necessary, only by picking the infested 

 leaves early in June before 

 the plant lice have begun to 

 escape and burning them. 

 This recommendation is 

 practical only in the case 

 of small trees. 



Our most common elm 

 gall is the cockscom^b gall 

 (Colopha ulmicola 

 Fitch) which is sometimes 

 so abundant on American 

 elms as to distort the foli- 

 age badly. The much rarer 

 slippery elm gall (Pem- 

 phigus ulmifusus 

 Walsh) is confined to the 

 red or slippery elm and is 

 easily distinguished from 

 the more recent introduc- 

 tion by its larger size and 

 particularly by its occur- 

 rence only on a very char- 

 acteristic food plant. The 

 smell of the leaves is often 

 sufficient to identify the 

 leaf and, secondarily, the 

 gall. 



Fig. II Slippery elm pouch gall 

 (natural size, original) 



