Importance of the Study of Galls 119 



probably only apparent, exception from this rule. In the 

 second place plants have no special adaptations for the 

 purpose of gall-formation ; the adaptations lie completely 

 with the parasite which works only with the characters 

 that belong to its host. 



But the galls are not at all restricted to the anatomical 

 elements of the organs on which they originate. Cells 

 which the plant otherwise forms in the bark of its stem 

 only, can frequently be found in the galls of leaf-inhabit- 

 ing Cynipids and Diptera. The same holds true for the 

 galls of the stem and the root. We may conclude from 

 this that the power of producing these elements belongs 

 not only to those organs which develop them normally, 

 but probably also to all the other parts of the plant. 



Worthy of special notice here are the roots which, for 

 the purpose of covering the galls of Cecidomia Poae, de- 

 velop in a place, where, in the normal course of develop- 

 ment, neither the plant bearing them, Poa nemoralis, nor 

 any other kind of grass, is able to produce roots. 31 Thus 

 the larvae here make use of a potentiality, the existence of 

 which we could never have conjectured, still less proven. 

 In Beyerinck's experiments, these gall-roots grew into nor- 

 mal, profusely ramifying roots; the cells of the internode, 

 stimulated to activity, must therefore have possessed, in 

 a latent condition, the qualities necessary thereto. 



Through the experiments of this investigator, even a 

 direct transformation of apparently somatic tracks into 

 germ-tracks has been, if not entirely accomplished, at 

 least brought quite near completion. 82 The galls which the 

 leaf -wasp Nematus viminalis, produces on the leaves of 

 Salix purpurca, possess an exceeding vitality. At the be- 



^Bot. Zeit. 1888. 1. c. 



32 Bot. Zeit. 46: 1, 17. 1888. 



