368 Transactions of the Canadian Institute [vol. ix 



in the undescribed sawfly gall on Salix serissima (Bailey) Fernald (Fig. 

 72). While I have made no attempt to determine by experiment the 

 cause of this unusual example of cell proliferation, yet it would seem 

 highly probable that the enzymes, introduced into the protoplasm by the 

 ovipositor of the producer and swallowed by the larva, have not entirely 

 lost their power by passing through the digestive tract but are still able 

 to excite cell division. 



The gall producer's influence works remarkable changes in the 

 affected part of the host; even apparently new tissues, glands, trichomes, 

 etc., make their appearance. The activity of its protoplasm is so much 

 increased that hypertrophy or hyperplasia is an invariable accompani- 

 ment of gall production. The conventional view to account for these 

 phenomena is that the protoplasm has been endowed with entirely new 

 characteristics and power to produce something foreign to the normal 

 host. But this is probably true only in a very limited sense, for according 

 to my experience at least the prototypes of such apparently new tissues, 

 etc., have been found elsewhere in the host or its relatives. Seemingly 

 the correct explanation is that not only are dominant characteristics in 

 the protoplasm stimulated but also in certain cases latent properties are 

 called into activity, and thus apparently new structures appear in the 

 host. Attention has already been drawn to examples confirming this 

 opinion, but the evidence will now be more fully elaborated in the case 

 of glands, trichomes and aeriferous tissue. 



It may be stated as an unvarying rule, that when glands are.present 

 in the normal tissue they are always more plentiful or larger in the gall 

 originating from that tissue. This is exemplified in the galls produced 

 by Eurosta solidaginis Fitch (Fig. 42), Aulacidea nabali Brodie (Fig. 66), 

 and numerous other species to which attention has been directed in the 

 descriptive part of this paper. 



But glands also occur in certain galls on parts of the host that are 

 normally glandless; thus they are plentiful in the gall produced by Neo- 

 lasioptera perfoliata Felt on Eupatoria perfoliatum L. (Fig. 23), but are 

 not found at the same location in the normal. At first sight they appeared 

 to be new structures, but were finally discovered in the normal host at 

 the base of the stem. In E. urticcBJolium Reichard they likewise occur 

 in the transitional region between stem and rooc, while in E. purpureum 

 L. they are present in the roots, petioles, and flowering axes as well as 

 in the cortex and pith of the stem. In the case of gland production it is 

 clear that not only have active characteristics of the protoplasm in that 

 direction been stimulated to an activity greater than the normal maximum 

 but nearly dormant properties have sometimes been aroused into action. 



