Brown : Algal periodicity 230 



in pond no. I, as large as a pea, light green and bladder-like. It 

 disappeared the last of December, appearing again the first of 

 April. It became very abundant during the last of April and the 

 first of May — the dominant alga. It began to be more rare the 

 last of May and had entirely disappeared by the last of June. 

 The animal life of the stream doubtless had something to do with 

 its disappearance. There were numerous tadpoles in the " branch " 

 and it was noticed that in pools in which there were many tadpoles 

 there was no Cliaetophora. The disappearance during the winter 

 was likely due to low temperature. 



Cliaetophora cndiviaefolia was found to be rather abundant, at- 

 tached to objects on the bottom in the upper part of stream no. I , 

 November 15, 1906. A little later it became rare, but persisted 

 in small quantities during the winter. In March it began to in- 

 crease in abundance, becoming very abundant about the middle of 

 April. This continued until about the first of June, when it began 

 to disappear. By the last of June, it had entirely disappeared. 

 This species was doubtless affected by the same agencies as the 

 preceding form. 



Draparnaldia phtmosa appeared in the upper part of stream no. 

 1 about the middle of November, 1 906 (see chart). It seemed to 

 be healthy and growing. It varied in abundance during the winter, 



being usually rather rare or rather abundant. Floods washed 



away large quantities, making it rather rare at times. Material 

 brought into the laboratory on February 16 showed numerous 

 zoospores in 24 hours. This plant reached its greatest abundance 

 in March. After this it began to disappear and by the last of April 

 had disappeared altogether. This plant appeared in several other 

 places, but in every case the conditions were very similar. It 

 seems to thrive in flowing surface-water at a temperature ranging 

 from o° to 1 5 ° C. In no case was the plant found in a pond. 



Two species of Myxonema were found, tenue and nanum. M, 

 namim persisted throughout the year without change on wet rocks 

 at outlet of sewer on campus. The conditions under which it was 

 growing were not subject to much change, the water being warm 

 continually, about the same in amount and always richly laden with 

 sewage. Myxonema tenue was first noticed in the lower part of 

 stream no. 1 April 18. The filaments were attached at one end, 



