TUBERCULAR SWELLINGS ON THE ROOTS OF VICIA FABA. 
553 
iiberhaupt mit einem Pilze, mit einem Scliizomyceten zu thun ” is not clear, but the 
author admits no other alternative. 
Brunchorst supposes the “ bacteroids ” to arise by differentiation from the proto¬ 
plasm of the cell, and Tschirch accepts this view ; the “ bacteroids ” (i.e., gemmules) 
are supposed to be remnants of a protoplasmic network (p. 68). Insuperable diffi¬ 
culties against accepting the view that the tubercles arise by infection from without 
are found in that it involves the assumption that the germs must be in all soils and 
in water, and Tschirch states (p. 69), “ Thatsachlich sind derartige geformte Pilze 
aber gar nicht im Boden vorhanden.” The “ bacteroids ” are thus denied autonomy 
as parasitic bodies, and are relegated by Tschirch and Brunchorst to the protoplasm 
of the root as “geformte Eiweisskorper.” 
Tschirch then goes further, and classifies these bodies with the vegetable caseins 
related to Legumin. 
The filaments (hyphse) observed by Eriksson and Frank, and which I have traced 
from the exterior, through the root-hairs and into the tubercle in Vicia Faba, are said 
to be absent from the cortex and outer tissues. “ Ich habe in der ausseren Bincle 
niemals Eiiden gefunden” (p. 72). They were observed in abundance, however, in 
the outer limits of younger “ bacteroid tissue.” 
Tschirch denies their fungoid nature entirely, and refuses to see in them either 
hyphse or plasmodial strands. His account of their “development” (pp. 73, 74) 
is quite unintelligible : among other things he regards the cell-walls of the tubercle 
as cutting these filaments (hyphse) in two. He thinks that no connection exists 
between the “ bacteroids ” and the filaments, but this is admitted to be doubtful. 
The view accepted—so far as any definite idea about the hyphse is accepted—is that 
the filaments dissolve, and the protoplasm of the cell then gives rise to the “ bacteroids ” 
by differentiation. 
Looking at Tschirch’s statements so far, it seems clear that, apart from the small 
amount of direct observation which has been brought to bear on these bodies, two 
chief points come in to explain the mistakes. In the first place, he has not examined 
tubercles sufficiently young to determine the course of the hyphse from without 
inwards; and, secondly, he has failed to observe the relations of the hyphse to the cells 
and protoplasm of the interior of the tubercle. 
Apart from the dying-off* of the older hypha which enters the young root-tubercle— 
often at a time when root-hairs are still present—it is, of course, obvious that many 
sections will not take in the point of entrance and the course of the hypha shown in 
my figures 8 and 9. Tschirch’s figures 1, 2, 4, and 44 show that the sections were 
made in the wrong direction to give the required information, and, although the 
tubercles examined are described as “ young,” they are far too old for the purpose 
referred to. Again, in the absence of some intelligible suggestion as to what the 
filaments are, if not hyphse, there is nothing gained by reiterating that “ mit einer 
Pilzhyphe haben sie also nichts gemein.” The assumption that they are cut in two by 
MDCCCLXXXVII.—B. 4 B 
