1893,] Symbiosis and Mutualism. 517 
Chytridium-like parasite in the cells of Jris which has never 
been seen since, and named it Schinzia. So when, in 1879, 
Frank first worked upon clover tubercle, he considered it sim- 
ilar to Naegeli’s Schinzia, and named it Schinzia leguminosarum. 
Subsequently, a tubercle was found on the roots of Alnus by 
Woronin, called by him Schinzia alni. Tubercles have been 
found in this country on the roots of Ceanothus, and are known 
on a few other plants besides the Leguminose. 
There has been considerable uncertainty as to the cause of 
clover tubercle and the nature of the parasite to which it is 
due. Schroeter took the parasite for a Myxomycete similar to 
Plasmodiophora and named it Phytomyza. Marshall Ward, in 
the article cited, compares it to the yeast fungi. De Bary, in 
1884, dismissed the matter with a sneer. Frank now puts the 
parasite among the Schizomycetes, and, indeed, the best view 
seems to be that the parasites are bacteria pure and simple. 
There are, in some tubercles, hyphe, or something very like 
hyphe, which Frank now calls “ Infektionsfaden.” Marshall 
Ward considered these the hyphe of which what some call the 
“ baktroiden ”—i. e., the bacteria—were spores. Schroeter saw 
in them a plasmodium. Frank, always unique and startling, 
has finally (1891) decided that the “ Infektionsfaden” have 
nothing to do with the fungus, but are products of the host for 
the purpose of self infection! These hyphe are usually filled 
with the “ baktroiden,” and Thaxter’s recent discovery of Myzxo- 
bacteria may throw some light upon their true nature. In an 
article in the Torrey Bulletin for July, 1892, Mr. Schneider 
concludes that these tubes have nothing to do with the bac- 
teria, or Rhizobia, as Frank now calls them, and considers them - 
hyphal fungi related to the parasite of Alnus tubercle. As 
these tubes often contain the bacteria, this seems improbable. 
-From all that I have read and seen, I am satisfied that the 
parasites are bacteria, and I see no reason for separating them 
from the rest of the Schizomycetes as Schneider does. I even 
doubt the necessity of creating a separate genus for them, as 
Frank did in 1890, under the name of “ Rhizobium” (Pilzsym= 
biose der Leguminosen). 
