Fresh Water Algae in Vicinity of Montreal 411 



were unnamed for lack of fruiting material but which 

 greatly resembled it, were found in different places 

 growing' fastened to stones in the water. Experiments 

 were made next with S- inflata Vauch, 8. orthospira 

 Naeg. and two unnamed species, all of which were 

 found free-swimming in nature. None of these were 

 apparently grown in culture media, but all were used 

 in contact cultures. While neither the attached nor 

 the free-swimming forms produced rhizoids when 

 grown in ordinary water cultures, it was found 

 that all could be induced to form these organs in a 

 few days by growing them in contact with some object 

 like a microscope-slide or cover-glass, in a drop-culture. 



To complicate matters, however, it was found that 

 several other species failed entirely to respond to the 

 contact treatment. These were S. Weoeri, 8. varians 

 and several unnamed forms, all of which were 

 found free-swimming in nature. Although all of 

 these were grown in contact cultures for over a month 

 none showed any sign of rhizoid formation. 



Spirogyra fluviatilis appeared to be the most highly 

 sensitive of all the forms examined, and readily formed 

 strong rhizoids. Other forms produced rhizoids more 

 or less freely in contact culture, 8. orthospira showing 

 the least response to treatment. It was on this 

 account, as the author explains, that 8. fluviatilis was 

 used for the majority of the experiments with culture 

 media. In no case could he discover the cause of this 

 phenomenon. In the rest of the paper, he discusses this 

 rhizoid-forming tendency in other genera, such as 

 Mougeotia, Ulothrix and Vaucheria, which show similar 

 differences to those observed in various species of Spiro- 

 gyra. 



A consideration of all the evidence, both in this 

 work and that furnished by my own observations of 

 the rhizoid-forming power of Spirogyra, leads me to 

 conclude that, in the first place, this phenomenon is 

 due to a certain specific sensitiveness rather than to 



