236 Brown : Algal periodicity 



came more healthy and thrifty looking and fruiting filaments became 

 rare. During December and January, the plant was rather abun- 

 dant in sort of a resting state — not growing any, living, but 

 crusty looking, due to particles of soil and diatoms clinging to the 

 filaments. A similar condition continued throughout February 

 and the first half of March, except that the plant became more 

 rare. Between my visits to the pond on March 14 and April 3, 

 considerable change took place. On the latter date there was in 

 the pond a considerable amount of the alga floating in unattached 

 masses. This seemed to be rather healthy looking and was just 

 beginning to fruit sexually, dwarf males being numerous. The 

 warm weather and sunshine of the latter half of March must have 

 caused vigorous growth and as the filaments became older and 

 longer they became free-floating. On April 16 this floating form 

 had become abundant near'the surface, especially around the edge 

 of the pond, and the fruiting organs were very abundant. This 

 began to disappear during the latter part of April and by the middle 

 of May had entirely disappeared. The part attached continued to 

 be about the same until the latter part of May, when it became 

 more rare, brownish and not very healthy looking. It remained 

 very rare and unhealthy until August. 



This alga did not appear in any of the other streams and ponds 

 under observation except in pond no. 2. It was found to be abun- 

 dant here October 1 1 — scattered all over the pond, some attached 

 to Eleocharis and Potamogeton plants but the most free-floating. 

 The plant became more abundant during the latter part of October 

 and the first part of November. In the latter part of November it 

 became unhealthy looking, less abundant, and settled to the 

 bottom. It disappeared altogether in the first part of December. 

 The floating masses were not observed fruiting. Some few of the 

 attached filaments bore sexual organs. The floating masses ap- 

 peared here as suddenly as in pond no 1. It disappeared more 



slowly ; the loose, floating masses were mainly washed out of the 

 pond. 



Oedogoniiun cryptoporum appeared in three different ponds, 

 nos. 3 and 4 and the larger of the water-works ponds, but not in 

 much abundance in any one. A small amount was found in 

 September, October, and the first part of November. Later in 



