No. e. DEPARTMENT OF AGRICULTURE 3CS 



lurv various opinions were held by different authors regarding these 

 bodies. The more general view was ihat they were of the nature of 

 fnngns growths, or otherwise diseased conditions of the roots: a few 

 held them to be the result of animal parasitism, and due either to 

 insects or worms: while others considered them to be normal organs. 

 regarding whose function there was difference of opinion. 



All of these latter views were, however, purely speculative, rather 

 than based upon any serious study: and it was not until 1S66 that 

 any attempt was made to study them closely: when Woronin'- de 

 scribed their microscopic structure. 



He found them to be composed of a cenn^al portion of thin walled 

 cells, of an outer rind, and of an intermediate layer or vascular ring. 

 In the central portion the contents were cloudy, and closer examina 

 tion showed the cells in this portion to be filled with peculiarly shaped 

 bodies, which were sometimes rod-like, at others forked, and present 

 ing a variety of forms simulating the letters T and Y. Woronin re 

 garded these bodies as living organisms, but since they differed from 

 other bacteria or Tl^/ro-^ in form, he termed them Bacteroids. He 

 regarded them as the causative agents in the formation of the tuber 

 cles, although he offered no proof of this assumption. 



In 1S74. Erickson" found in the newly developing tubercles long 

 branching filaments resembling the mycelium of a fungus. These 

 threads he considered to be the infecting agents. Later on in the 

 development of the tubercles he obserxed the presence of the bac- 

 reroids. noted by Woronin. but failed to connect the two as corelated 

 structures. 



In the early observations of Woronin and Erickson we have the 

 germ and substance of all that has since been discovered regarding 

 root tubercles. Both recognized, as is held to-day. the two classes 

 of bodies the filamentous and the bacteroid. Both were right in as- 

 suming that the organisms as seen within the tubercles were the 

 agents in their production, although Erickson was more nearly right 

 in assuming that the filaments were the real infecting agents. 



But it was left to others to show the relation of the filaments ro 

 the bacteroid bodies, and this question became the subject of much 

 controversy and difference of opinion extending over many years. 

 In the controversv which followed, covering the latter 2-5 vears of 

 the nineteenth century, the most eminent botanists were engaged. 



On certain points they agreed, on others they differed, but since 

 the points on which they differed determined the position which 

 these forms should occupy in a system of classification, the subject 

 became of especial interest. 



All agreed to the presence of the filaments within the tubercles 

 in the early stage of their development. These filaments were fur- 



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