148 Conservation Department 



Heterokontae. — Botryococcus appeared in traees near the sur- 

 face at the south station on August 26. This plant was not seen 

 in any other locality on the lake during the entire summer. In 

 1921 Botryococcus formed a very conspicuous "bloom" on the 

 surface along- the east shore of Cayuga lake. 



Bacillariae. — The great bulk of the phytoplankton consisted of 

 diatoms represented by three genera, Asterionella, Fragilaria, and 

 Tabellaria. All three of these diatoms were most abundant in the 

 upper 5-10 meters and relatively scarce below the 25 meter depth. 

 Asterionella was most abundant in the spring and early summer 

 and decreased in numbers so that by September it occurred only 

 in traces. In plankton samples taken at the south station in early 

 spring, Asterionella was the most dominant form observed. The 

 following figures, from the 0-5 meter depth, give an indication of 

 the rapid decline of Asterionella in numbers per liter of water: 

 April 16, 3,765; May 14, 1,913; June 16, 987; June 30, 339; July 

 14, 216. This indicates the necessity of extending the observations 

 over a considerable period of time in order to obtain some idea of 

 the importance of any one form occurring in the plankton. 

 Fragilaria was relatively rare early in the season when Asterionella 

 was most " abundant, but became very abundant in August and 

 early September. Tabellaria occurred at all times. It showed 

 some decline but no striking change in numbers in the period 

 during which samples were taken. 



Nannoplankton. Cyanophyceae. — The most common blue-green 

 algae in the nannoplankton was Coelosphaerium rather abundant 

 during August. Oscillatoria appeared at both stations early in 

 the season, but was not seen after the middle of July. Qloeocapsa 

 and Aphanocapsa appeared rather irregularly. Merismopedia was 

 found in only two samples from near the surface at the south 

 station. 



Chlorophyceae. — No members of this group at any time formed 

 any dominant part of the nannoplankton. Scenedesmus seemed 

 to appear most frequently. It was found between 0-20 meters. 

 Characium, Crucigenia, Cosmarium, Bictyosphaermm, Eudorina, 

 Gloeotaenium, Lagerheimia, Oocystis, Pediastrum, Quadrigula, 

 Sphaerocystis, Staurastrum, Tetraedon and Volvox were found 

 one or more times but never appeared very abundantly. 



Bacillariae. — The most abundant diatom was a small Cyclotella 

 which was present in nearly all samples. It was abundant from 

 the surface to the 50 meter depth. Synedra appeared at all depths. 

 It was more abundant early in the season than later. Melosira 

 appeared at all depths early in the season but later was more 

 common in the lower samples. Stephanodiscus appeared in only 

 two samples at the north station. In addition to the above 

 diatoms, fragments of Asterionella, Fragilaria and Tdbellaria were 

 often found in the nannoplankton in considerable numbers. 



Protozoa. — Small numbers of Difflugia were found in several 

 samples from various depths. Fragments of Binobryon colonies 

 small enough to pass through the net were very numerous during 



