617 



On table II we have grouped together the plant- organ isms 1 of 

 all the lakes which have been examined, and when we except Sor- 

 vaagsvatn, the result is very poor. In the large lake near Ejde and 

 in the lake in Kvanhauge only, were found some indications of 

 true plankton; the others hardly contained any plankton-organisms, 

 Iml only algæ, not particularly characteristic of plankton. 



Il is a well-known faet 2 that Desmids are olien surrounded by 

 a mucilaginous envelope, and in the Færoes we have found lliis 

 lo be the case with the plankton-forms, spec. Staurastra, Xanthidia, 

 and some Cosmaria, hul nol Closteria. It is also the case with 

 some of the Chlorophyceae, vi/.. Sphaerocystis, Gloeocyslis, Cracigenia 

 and Raphidium, and the diatom Cyclotella. 



Notes on some of the forms enumerated in the tables. 

 I. PLEUROCOCCOIDEAE. 



1. Sphaerocystis Schroeteri Chodat, Etudes de Biologie lacustre 

 (Bul. de l'Herb. Boissier 1897, p. 292). 



There is hardly any doubt that what we have previously cailed 

 Eudorina elegans (Borgesen, Freshwater Algæ, p. 2158), and in a 

 measure also Pandorina Morum, which are found in plankton from 

 Sorvaagsvatn and the lake near Ejde, are stages of development of 

 lliis alga; Eudorina shonld thcrefore be omitted from the list of 

 the Færoese algæ. 



2. Oocystis spec. 



An Oocyslis which appears to hear a very close resemblance 

 lo Borge' s figure (Borge, Schwedisches Susswasser-plankton , Bol. 

 Notitser, 1900, p. 5, lab. I, lig. 3) was found occasionally in a sample 

 from the lake in Kvalbo Ejde. The colony consisled of four cells. 

 Long. cell = 16 n\ lat. cell = 11 /*; crass. fam. — 29 p. 



3. Scenedesmus hystrix Lagerh. 



A few specimens of this species were found in some of the 

 plankton-samples. As pointed out by Chodat (Algues vertes de la 

 Snisse, p. 215) Se. denticulatus Lagerh. should probably be referred lo 

 lliis species, hence it is also probable that the Se. denticulatus ligured 

 by Borgesen (I. c. lab. X, tig. 5) oughl lo be placed under Ibis species. 



1 The frequency of their occurrence is hulicateil ;is customary; see Osten- 

 feld s paper above. 



'-' See, e.g.Schroder Bruno: Untersuchungen uber Gallertbildungen der Algen. 

 Verh. d. Naturhist.-Med. Vereins zu Heidelberg. N. F. VII. '.!. 1902. 



