618 MINNESOTA BOTANICAL STUDIES. 



After twenty-four hours, the zoospores were much more num- 

 erous and showed a much greater rapidity of motion than here- 

 tofore. At 8 o'clock A. M. they were in rapid motion, and 

 remained in that condition for four or five hours. This was in 

 all probability due to their exposure to fresh air and sunshine. 



The usual method pursued in staining for the cilia was 

 that of Zimmerman (I) with slight modifications. A mount was 

 obtained in which the moving spores were numerous. After 

 being fixed with the fumes of osmic acid, they were allowed to 

 dry on the slide, and afterwards covered with a drop of aqueous 

 tannin solution which was washed off with water after five 

 minutes. Next the slide was left three minutes (Zimmer- 

 man advises fifteen) in a concentrated aqueous solution of car- 

 bol-fuchsin. This was again washed off with water and then 

 the slide left to dry. A drop of canada balsam and a cover- 

 glass being added, a good permanent mount was obtained. 



Another method for showing the cilia distinctly was acci- 

 dently discovered. In attempting to stain the nucleus in the 

 vegetative cells, Zimmerman's fuchsinmethyl-green method 

 was used. As a nucleav stain it was a failure, in this instance, 

 but the ciJia of zoospores contained in the mount were shown 

 very clearly indeed. By this method a spherical zoospore 7.5 

 mic. in diameter showed four cilia which were 13 mic. in length. 



In a cell from an upright filament from pebble "4", a spore 

 was seen 10 mic. in diameter. In the adjoining cell were two 

 ellipsoidal spores 7 mic. in diamter. This is the only instance 

 in which a spore of this size was observed within a cell. A 

 number of motile zoospores, however, resembled this one in 

 size, shape and general appearance. They moved slowly. 

 Moreover they possess only one eye- spot as far as observed. 

 By far the greater number of zoospores were 5-7.5 mic. in diame- 

 ter and egg-shaped. But these larger ones were abundant 

 enough to allow of examination. 



By means of the carbol-fuchsin stain many mounts of spores 

 were prepared and studied. In one instance the cilia measured 

 20 mic. in length. 



The glass dish containing the two pebbles upon which the 

 Stigeoclonium megazoospores were being produced so abund- 

 antly, occupied a position upon the outer window ledge, so 

 that the light was received from but one direction. On the 

 outer side of the vessel bright green patches lying at the 

 height of the water level were noticed. Upon examination 

 they proved to be masses of young Pilinia plants. The re- 



