— 239 — 



and J. Holinboe^) contain a few scattered notes on the plankton- 

 organisms; but a general treatment of the plaiikton-tlora of one or 

 several lakes has not yet been published. In Wi lie's last paper, 

 and in the paper by Holmboe most of the plant-organisms found 

 in Harsjon and in Lomnsessjon liave been recoj'ded from Norway, 

 but there are a few more wliich may be added to the list and 

 which I shall enumerate below together with notes on some of the 

 forms already recorded. 



Notes on some of the forms found in the samples. 



I. Chloropliycese. 



Spliserocystis Schroeteri Ghodat. This peculiar Pahnellacea occurred 

 in great numbers in both samples from Harsjon. The greater part of 

 the different stages figured by Chodat (Algues vertes de la Suisse, Bern, 

 1902, figs. 50 and 53) have been observed. 



Chlaiii,Ydoiiionas sp. (?). On the surface of the mucilage of Sphcero- 

 cystis a small green alga was often found ; it consists of a few or several 

 small isodiametrical cells, lying closely together, so that their cell-walls 

 become a little polygonal ; their diameter is about 5 // , and they contain 

 starch. As 1 had only preserved material for examination, I have not 

 been able to determine this alga, but the layers have a great resemblance 

 to the ,etats larvaires" of ChUimydomonas Reinhardi which Ghodat (I.e.) 

 has shown in figs. 54, _/ — / and 55, m—n. Perhaps they belong to the 

 same alga of which I found the resting-cells, and which I have called 

 Trochiscia sp. in the table. Professor Wille'-) has lately pointed out 

 that the Trochiscia probably is the resting-stage of Chlamijdomonas. 



Criicigenia rectangiilaris (A. Br.) Ghodat. In the sample from Harsjon 

 of the 8*^ of August 1899 this alga was rather common in its typical form, 

 like Ghodafs fig. 126 (I.e.). But in the sample of the 17'^ of July 1900 

 I saw one colony only, and it contained many and more irregular cells 



■) Holmboe, J.: Unders0gelser over Norges Ferskvandsdiatomeer, I. Diatonieer 

 fra Indsjoer i det sydlige Norge. Arohiv for Matliematik og Naturvidenskab 

 XXI, Nr. 8, 1899. 



') Wille, N. : Studien ul)er Chlorophyceen, Ghristiania Vidensk. Selsk. Skrifter 

 1900. Nr. H, Ghristiania 1901, p. lii. 



