[pENHALLow] A BIRCH ROPE 249 



compression is expressed in the formation of the nodal areas of paren- 

 chyma, as well as in the local consolidation of the cork tissue accom- 

 panied by an obliteration of the absciss layers. Upon reviewing all the 

 circumstances connected with this very remarkable tumour, we are 

 brought to the following final conclusions : 



1. The outgrowth had its origin in a lesion of the living bark, the 

 precise nature and origin of which cannot be ascertained. 



2. A definite hypertrophy developed as a traumatic reaction, but 

 instead of becoming localized and forming wood or sclerotic tissue, it 

 continued its development as active parenchyma and forced its way 

 through the overlying and external tissue of the periderm. 



3. The form of the outgrowth suggests that it emerged through 

 a lenticei as a region of minimum resistance. 



4. The probable relation of the outgrowth to a lenticei, suggests 

 that it may have had its origin in the spongy parenchyma which forms 

 the aeri ferons tissue of the lenticei. 



5. The outgrowth may be regarded as a special form of tumour, 

 the particular character of which was determined by the nature of the 

 surrounding parts, and particularly by the possibilities of ready exit 

 through a lenticei. 



6. The tumour developed by simultaneous division and enlarge- 

 ment of the component cells, throughout its entire length, and it was 

 completed within the limits of one season of growth. 



7. The formation of cork proceeded more or less simultaneously 

 over the entire surface until final exhaustion of the parenchyma. 



8. The primary cause of the tumour should be sought in a lesion 

 of the living bark, comhined with conditions of high temperature and 

 high atmospheric humidity. 



