THE FUNGOUS ROOT-TUBERCLES OF CEANOTHUS 

 AMERICANUS, ELAEAGNUS ARGENTEA, AND 



MYRICA CERIFERA.* 



KY E. G. ARZBERGER 



. INTRODUCTION. 



Although considerable work has been done by several in- 

 vestigators on the peculiar root-tubercles found on the alder 

 and some other plants, no satisfactory account of their 

 nature, origin, and function has yet been fully set forth. 

 Especially the question of their relation to the so-called my- 

 corrhiza remains to some extent unsolved. The following 

 studies were undertaken with the hope of getting fuller in- 

 formation regarding the 



cytology of the forms which occur on the roots of Ceanothus, 

 Elaeagnus and Myrica. 



gross structure, physiology and 



HISTORICAL. 



A brief resume of the leading views concerning the root 

 tubercles, from a historical standpoint, is interesting from 

 the fact that, for more than three decades, these structures 

 on the alder were described by various investigators, none of 

 whom proceeded far enough to determine the true nature of 

 the tubercles and the fungus which causes them. 



Meyen, (23) in 1829, gives the first description of the 

 tubercles on the alder and considers them as "pseudomor- 

 phosed roots," in the ends of which there is a parasitic 

 growth comparable to that of Lathraea, Rafflesla and BaUmo- 

 phora, though of a more primitive nature and in many re- 

 spects resembling growths of a parasitic origin, found in an 

 animal body. He claimed that the tubercles are formed 

 when the alders grow near flowing water and in shad 

 places. 



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* A thesis submitted to the Faculty of Washington 

 candidacy for the degree of Master of Arts, June, 1910. 



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