FUNGOUS ROOT-TUBERCLES. 



61 



Schacht (32-37) in each of his six productions on plant 

 anatomy and physiology, refers to the tubercles found on 

 the alder. He sets forth their morphology with description 

 and illustrations, and at first states that they are only normal 

 growths, but in later articles he considers them as abnormal 

 growths of the roots; however, no fact or theory regarding 

 an organism which may cause them is presented. 



Dobner (8), in his Lehrbuch, mentions the tubercles 

 formed on the roots of alder seedlings and regards them as 

 roots altered by much branching and thickening. No refer- 



in 



Jager (18) 



tubercles as insect calls similar 



to those found on the twigs of the willow and the pine. 



Rossmassler (31), in his description of the roots of the 

 alder, mentions the rusty-brown cluster-like outgrowth found 



large and small alder j 

 Tn 1866 Woronin (56) 



described and presented 



ures of the fungus that produces the tubercles on various spe- 



cies of the alder. He 



posed 



alni 



ma 



cles and stated that two organisms, one resembling Plas- 

 modiophora brassicae and another a filamentous type, 

 may be present in the cells. In the latter view he was 

 supported by Moller (24), who called 



the fungus Plas- 



mo 



Ratzeburg (30) refers to the abundance of tubercles on the 

 alders and gives a full description accompanied with plate 

 figures, some of which were borrowed from Woronin. He 



ism 



will be found in the cells. 



Moller (24) supported the views of Woronin regarding 

 the nature of the fungus and proposed the name Plas- 

 modiophora alni. Five years later (25, 26) he reinvestigated 

 fresh material and retracted his earlier views in favor of those 

 set forth by Brunchorst (6), who, by a thorough investiga- 

 tion, arrived at the true nature of the fungus in a study of 

 the tubercles of Alnus and Elacagnus. With a more modern 

 technique he was able to determine the mycelial nature of 



