82 MIDLAND NATURALIST. 
The ‘‘Knee-Joints’’ of Species of Mougeotia. 
During the spring of 1907 I was fortunate in obtaining some 
good conjugating material of Mougeotia scalaris ( Mesocarpus scalaris) 
specimens of which were sent to a professor in one of the western 
universities. The plants were said to be the most typical he had 
met with, and he called my attention to the fact that he seldom if 
ever had found this plant in any other condition except that of 
the formation of the ‘‘knee-joints.’’ From the context of his 
remarks I was led to believe that he considered this formation of 
the often observed ''knee-joints'' of this plant as a stage preparatory 
to, if not an actual stage of the process of conjugation. As I had 
not devoted much time to the subject before my attention was called 
to this phenomenon, and being well. acquainted with all the stages 
of conjugation of Mougeotia scalaris (Mesocarpus scalaris) and 
Mougeotia mirabilis ( Pleurocarpus mirabilis) I became very much 
interested in the problem and sought the very next occasion to try 
to gain some information of the phenomenon of the formation of 
the ‘‘knee-joints.’’ I had often seen these angular contact forma- 
tions in vegetative filaments of these plants, and my very first 
suspicion as to the nature of them and their meaning was that 
whatever biological interpretation might be put upon them they 
certainly were not a preliminary stage in the process of conjugation. 
In fact after studying carefully all the stages in this formation of 
the zygospore of either species of Mougeotía mentioned, of which I 
had an abundance of splendid material in every stage of conjugation, 
I was sure that the ‘‘knee joints’’ were not conjugating stages. 
After consulting Dr. G. S. West I was informed that the '' knee- 
joints'' as a problem was not thoroughly understood and presented 
an interesting phenomenon to be investigated. 
at the process mentioned is not a stage of conjugation, which 
I think many believe, is evident from the fact that the sexual 
process of the formation of zygospore is quite different. Of course 
in Mougeotia mirabilis this is self evident because conjugation 
almost without exception takes place between adjacent cells in the 
same filament, the zygospore, being formed in the protuberance 
between the two cells. ‘‘ Knee joints’’ are always formed by the 
distinct filaments of cells approaching one another, and forming an 
angular contact between a cell of one filament with one of another 
filament. The bend is usually only in the cells that come in con- 
