CHARACTER OF THE TUMOR. 159 



is dissimilar and whether the metastases partake of the nature of the 

 original tumor are subjects requiring much further study. 



In sensitive tissues the tumor reaction begins at once, and can be 

 seen as a slight elevation about the needle pricks as early as the fourth 

 or fifth day, and in the form of perfectly developed, small, fleshy 

 growths a few days later (daisy, peach, etc.). 



STRUCTURE AND GROWTH OF THE TUMOR. 



The gross appearance of these tumors when they occur on crucifer- 

 ous plants somewhat suggests the "finger and toe" attributed to 

 Plasmodiophora hrassicae. It is not a remote inference that all phe- 

 nomena of this character on the roots of crucifers should be attributed 

 to bacteria, particularly as no clear-cut inoculations with Plasmo- 

 diopliora have ever been obtained. By this is meant inoculations 

 which would clearly exclude the possible presence of pathogenic 

 schizomvcetes. But the chances are against such being the fact. 

 We have not made enough experiments to be able to say positively 

 that crown-gall bacteria never occur associated with the Plasmodio- 

 phora, but in opposition to this view, and favorable to the autonomy 

 of the finger and toe disease, is the structure of its tumor, which 

 shows very little hyperplasia and a great amount of hypertrophy, 

 especially of the cells occupied by the spores of the Plasmodiophora. 

 Moreover, the phloem is a favorite point of attack in finger and toe. 

 Probabh^ the correct view is that these are two distinct gall diseases 

 of crucifers. Writers on malignant animal tumors are correct in 

 asserting that the Plasmodiophora tumor is anatomically quite unlike 

 the tumors with which they have to deal. 



The anatomy of the crown-gall having proved a much easier sub- 

 ject than the etiology, there is a considerable body of literature 

 respecting the structure of the galls, the details of which need not 

 here occupy much space, since we contemplate a special paper on the 

 subject. Those who wish to know more may refer to the following 

 authors for structure of the tumors of the plants specified: Almond 

 and peach (Toume}') ; rose (Scalia) ; sugar beet (Briem) ; raspberry 

 (Wulff ) ; poplar (Brizi) . The contentions of these writers agree in 

 the main, and the principal facts set forth by them are not contra- 

 dicted by anything we have observed. 



Some additional observations and inferences may here find place. 

 In crown-gall we may assume either (1) a direct stimulus to growth 

 or (2) an indirect one through the removal of some normal inhibition. 

 Probably the first is the true explanation. The tumors appear to be 

 able to arise from any meristematic tissue, i. e., from any cells of 

 the organism which are able to divide. They are not subject to 

 any physiological limitation. In a way, of course, the growth that 



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