20 R. Gronblad, New Desmids. 



well as dwarf forms of M. truncata with perfectly typical 

 cells (cf r. B o r g e, Sao Paolo p. 66 : length 55 — 65 // ; W o 1 1 e, 

 Desm. U. S. p. 114: length 50—100// „var. minor Wolle"; 

 Lagerheim, Amer. Desm. p. 230: length 42 — 44// „v. mi- 

 nor Wolle"). The typical M. truncata is in Finland com- 

 monly more than 100// (90 — 115), in England (cfr. West, 

 Mngr. II p. 83) it is 87—138//. 



In Finland M. decemdentata has not been recorded 

 earlier. — [Elfving has (Desm. Finl. pi. 1 f. 1) figured an 

 abnormal Micrasterias in which one semicell is typical of 

 M. pinnatifida, whereas the other resembles var. inflata 

 Wolle (Desm. U. S. pi. 37 f. 9) or f. quadrata Turn., (E.- 

 Ind. pi. 5 f. 3 b). Thus the author is not right in saying: 

 „altera semicellula characteres M. incisae, altera M. pinnati- 

 fidae praebet."; and M. incisa therefore is not known to 

 have been found in this country.] — I have seen this species 

 from only two localities in SE-Finland and it is one of our 

 rarest Micrasterias. Long. 46 — 51, lat. 51—60, crass. 14 — 16, 

 isthm, 9//. N:o 1283]. 



Mab. Antrea (SE). PI. 1 fig. 1—3. 



M. truncata (Cord a) Breb. and var. crenata (Breb.) 

 R e i n s c h. 



These forms, originally described as two separate species, 

 have been united by several authors, the former always 

 being regarded as the type and the latter as a variety of 

 this. Already Ralfs (Brit. Desm. p. 75 — 76) expressed this 

 view, later also Archer (Q. J. M. Sc. n. s., vol. 5, 1865 

 pag. 257). The first who really united them to one species 

 was Reinsch (Alg. Flor. Frank. 1867 pag. 143—144); also 

 Rabenhorst (Flor. Eur. Alg. Ill p. 191); Cu s h m an (New 

 Engl. Micrast. 1908 p. 102); Cedergren (Arkiv f. Bot. 

 1913 p. 16—17); Borge (in litt. 4 5 1919). Contrary to 

 these authors Mssrs W. and G. S. West (Mngr. II p. 86) 

 are pointing out the considerable difference between ty- 

 pical specimens of M. truncata and M. crenata; but they 

 also admit the existence of many transitional forms. Accord- 

 ing to the description given by West M. crenata should 



