602 MINNESOTA BOTANICAL STUDIES. 



its foothold until the present time, a letter was sent to the 

 postmaster at Bellefonte, Mr. David F. Fortney, asking his aid 

 in procuring some specimens. He replied that the spring was 

 thoroughly cleaned at intervals and for that reason it might 

 not be possible to find the plant, but that if it existed, it should 

 be sent me. Upon his recommendation I then communicated 

 with Miss Ella Levy, the teacher of Botany in the Belle- 

 fonte High School, explaining as well as possible the probable 

 nature and appearance of the growth. It was feared that even 

 if it were still in existence there would be a difficulty in recog- 

 nizing the Pilinia among the many other algal forms which 

 would naturally be its neighbors, since from the frequency of 

 the cleaning process, it could scarcely have time to form the 

 crust which would have distinguished it. 



Miss Levy forwarded two pebbles taken from the bed of the 

 spring, without very much hope that the Pilinia would be found 

 on them. However, they proved to be covered with an algal 

 growth unmistakably identical with that described by Dr. 

 Wood. The question of whether the plant was a Pilinia or not 

 called for further investigation. Later an abundance of the 

 material was secured. 



Some of these pebbles were kept in tanks during a period of 

 two months, the water being changed frequently. By the end 

 of that time, the plant itself had solved the problem of its iden- 

 tity in the most effectual manner possible by simply transform- 

 ing itself into a common Stigeoclonium. When this fact was 

 proved, an effort was made to look up the literature concern- 

 ing this genus. Finding that, though of long standing, it 

 had not been made the subject of much research, it was 

 thought that it might be well in giving the results of these in- 

 vestigations upon the Pilinia stage, to include whatever facts 

 had come under observation relating to the Stigeoclonium and 

 Palmella stages. The microscopic structure and development 

 of the plant will therefore be considered under three heads: 1. 

 Pilinia stage. 2. Stigeoclonium stage. 3. Palmella stage. Since 

 in the first named stage there is certainly a distinct adherence 

 to Pilinia characteristics, as furnished by Kuetzing, a brief 

 history of this genus is given with the idea of showing the 

 possibility of truth in the theory offered by Wille (I) viz.: 

 That the genus Pilinia is made up of species which represent 

 stages of other algae. It is not so easy to accept his further 

 statement that these are of the Phycochromaceae. 



