54 



MISSOURI BOTANICAL GARDEN. 



at all and in these cases it was very slight. Nevertheless no 

 conjugation had taken place and there was none observed 

 subsequently. Despite the precautions, mycelium developed 

 in these cultures and soon affected the algae. 



Spirogyra longata was the most abundant form through- 

 out the greater part of the period during which the work was 

 being carried on and served for a large number of experi- 

 ments. During January, February, and the early part of 

 March it seemed to be confined to a region near the source 

 of a small stream that arises from an artificial pond in the 

 Garden. Late in March it spread into the pond and down 

 the brook and in April and May became excessively abund- 

 ant. The environmental conditions certainly varied greatly 

 during this period but only a very little conjugating material 

 could be found, although in the same brook S. Grevilleana 

 and possibly also S. porticalis, appeared, conjugated, and for 

 the most part disappeared. Despite its apparent hardiness 

 under natural conditions S. longata proved rather a difficult 

 species to handle in the laboratory. When brought indoors, 

 especially during the winter, it almost invariably grew rap- 

 idly for a few days, then suddenly fragmented and died. It 

 acted in the same manner in a number of media, in bright 

 or subdued light, and under somewhat varied conditions of 

 temperature. Later in the season this tendency was much 

 less pronounced. It was found, however, that even during 

 the winter if flasks containing the cultures were placed at 

 once in the brook the plants did not die and could subse- 

 quently be returned to the laboratory where they would then 

 live for a long time. Later it was noticed that the addition 

 of a slight amount of NH 4 N0 3 a day or two after the plants 

 were first brought to the laboratory served to prolong their 

 life and stimulate growth, but of course this method could 

 not be used with material intended for experimentation. 

 Attempts to induce conjugation were without success except 

 where the stock material had already shown at least incipient 

 stages before the work was begun. Seventeen of the Benecke 

 solutions were made up in melted snow, S. longata was added, 



and the aquaria (flasks) were kept in the stream from March 





