Brown: Algal periodicity 231 



tation resulting from cormophytic plant growth the previous 

 summer, and the refuse from the pumping station near by, tended 

 to make the water here impure. This was fruiting freely when 

 found and was not found afterward. 



Spirogyra Weberi was found in the upper part of stream no. i 

 in October in very small quantities and it was rather abundant in 

 pond no. 3 during September and October. It became rare the 

 first of November and disappeared later in the month. No con- 

 jugation was noticed although it might have taken place in short 

 time and the whole plant growth disappeared, or it might have 

 been so scattering that it was not noticed, the plant not being very 

 abundant. A few other species were found in small quantities 

 but no attempt was made to follow them in their periodicity. 



Among the filamentous forms of Conjugatae, Zygnema ranked 

 next to Spirogyra in abundance and distribution. It was found 

 in some quantity in several of the ponds but not in great abun- 

 dance in any case. In stream no. I, Zygnema insigne appeared 

 during October, became rather abundant, then gradually disap- 

 peared in November. It was not observed to fruit. On April 

 1 8, Zygnema leiospcrmum was found in the upper part of the stream 

 just below a pond in which the species had been growing. It was 

 rather rare, not growing or healthy looking, and was fruiting to 

 some extent. This species continued to be present in small quan- 

 tities until the first of August. The same species was rather abun- 

 dant in pond no. 3 during the latter part of September, 1906. It 

 was pale-green and unhealthy looking, and mixed with Spirogyra. 

 It became rare during October and disappeared the first of No- 

 vember. A few scattering filaments of Z. leiospermum were found 

 >n pond no. 2 during November, 1906, and also during the following 

 May. Z. cruciatum was found to be rather abundant in pond no. 1, 

 March 14. It was not very healthy in appearance and remained 

 in about the same condition until the latter part of May, when it 

 began to grow, became more healthy, and more abundant. It 

 was along the edge of the pond in shallow water — some of it 

 floating. This disappeared in June. 



Mougeotia was not very abundant at any time in the waters 

 under observation. A few species were found in limited quanti- 

 ses. Mesocarpns radicans was found on April 4 in small quantity 



