yi6 



and found similar cases likewise in older plants of Pscndotsuga Dotiglasi, 

 Abies fraseri and Abies concolor, which showed swellings of the bark. 

 These could be proved to 1)C a lysigenous widening of schizogenous resin 

 canals. The trees stood on moist, marshy soil which had been heavily 

 manured at intervals of two or three years. 



Recently, I have had opportunity to observe resinosis as a constitutional 

 disease, i. e. as the manifestation, even in old trees, of a tendency throughout 

 the whole plant body, to form resin excessively. I have distinguished this 

 universal disease, as "chronic resinosis," from the "acute resinosis" pro- 

 duced locally as a result of wound stimulus, and remaining localized, which 

 is connected with the exudation of profuse amounts of resin^ Accordingly, 

 in the future, a chronic and an acute gummosis would have to be distin- 

 guished from one another and in 

 the latter, the treatment of the 

 wounds with vinegar, already 

 recommended, might be success- 

 ful. 



I'oK.MATION OF Rf.SIN IN 

 DlCOTYLKDONOUS PlAXTS. 



The production of resin and 

 gum resin in dicotyledonous 

 plants is found to be parallel to 

 the processes descril)ed in the 

 ]jreceding section. Svendsen" 

 found that the gum resins of 

 Sty rax, Licjuidamber, Toluifera, 

 etc., are pathological products, 

 produced as a result of injury. 

 After every injury, which ex- 

 tends as far as the cambium, 

 wound wood is formed which is distinguished by its tracheidal, parenchy- 

 matous character and which gradually passes over again into normal wood. 

 The processes, therefore, are ever}^where the same, just as was described and 

 illustrated under injuries due to the frost. The wound stimulus makes itself 

 felt in the old wood by a stoppage of the ducts with tyloses, or the closing of 

 them by Bassorin. The new wood, wdiich is formed about the wound and at 

 first is parenchymatous, has resin canals produced schizogenously ; and 

 widening lysigenously. The resinosis thus attacks the w^ood parenchyma, 

 with the exception of considerable parts of the medullary rays, and con- 

 tinues later in the bark, where it becomes noticeable within the bark rays ; a 

 fact which should be emphasized. In dicotyledons, as in conifers, the patho- 



Fig. 161. Group of parenchyma cells from 

 the outer bark which has been completely 

 separated from the central wood cylinder by 

 the turning to resin of an annular, abnormal 

 zone of wood parenchyma. The nuclei may 

 still be discerned in the bark cells. (After 

 Conwentz.) 



1 Landwirtschaftliche Jahrbiicher 1908. 



2 Svendsen, Carl Johan. tJber den Hai'zfluss bei den Dicotylen, speziell bei 

 Styrax. (\marium, Shorea, Tohiilera und Lifiuidambar. Archif for Mathematik og 

 Naturvidenskab. Kristania 1905. Vol. XXVI, No. 13. 



