294 TAYLOR— ON THE PRODUCTION OF 



These proliferations were frequently irregular, and then from them 

 no differentiated tissue arose. 



At times under favorable conditions there was formed in these pro- 

 liferated regions a cambioid zone, that laid down tissue in a manner 

 resembling that of normal cambia. 



From zones of this kind that were formed from cortical cells, cork- 

 like protective tissues were produced. 



As a result of severe injury to the stem, the innermost cortex pro- 

 duced xylem patches that seemed to correspond to the " extra-fascicular 

 bundles" of Schilberszky. 



The only proHferation of phloem cells that was produced was an 

 irregular one and concerned also the cambium and probably the young 

 xylem cells. There was a suggestion of the resumption of cambial 

 activity in this region. 



The xylem, besides being concerned in the above reaction, was able, 

 when it had not been lignified, to proliferate. 



The pith responded readily while young, and there was formed 

 after proliferation a cambium that laid down xylem, and possibly also 

 phloem, around the pith cavity. 



Conclusions 



As a result of these experiments, the writer would consider that all 

 the elements of the normal stem are capable of extensive multiplication 

 unless they have been modified by cuticularization, lignification, or 

 suberization. Cells that are collenchymatous are, notwithstanding, 

 able to prohferate freely. From these proliferated areas there may be 

 formed cambioid zones that give rise to cork, to xylem, and possibly, 

 to phloem. The initial multiplication may be started by mechanical 

 or chemical means. The chemical irritation, if it suffices to cause tissue 

 destruction, may have an ultimate effect similar to a mechanical irrita- 

 tion. 



BIBLIOGRAPHY 

 This list contains only those works found most helpful to the writer. Where an 

 author has been mentioned in the text, but is not referred to in the bibliography, it 

 is to be understood that a synopsis of his work is contained in Kiisters "Pfianzenana- 

 tomie." 



(1) Kuster, Ernst "Pathologische Pfianzenanatomie" Jena, Gustav Fischer. 



Zweite Auflage, 1916. 



