22 R- Gronblad, New Desmids. 



the commonly 5- (sometimes 2—7-) spinate or dentate upper 

 and lower lateral lobes, which are not divided into sublobes. 

 — A synonym to this variety seems to be M. crenata by 

 Stange (Micr.-formen, fig. XV). 



Long. 103—106, lat. 91 — 103, crass. 49, isthm. 19—25/'. 

 [N:o 809 a]. 



Hab. Keuru (C). — PI. 1 fig. 9—10. 



var. semiradiata (Kiitz.) CI eve; Nageli (Gatt. einz. 

 Alg. t. 6 f. H 3). The species described by Nageli is 

 nothing but a form of M. truncata. Whether this form 

 should be separated as a systematic form is somewhat 

 doubtful, as there are also transitional forms. But the 

 original form, as described by Nageli, seems to be so 

 characteristically distinguished by the shape of its polar 

 lobe and by the longer and slenderer spines at the margins 

 of all lobes, that it could quite well be separated as a 

 systematic form : var. semiradiata (K ii t z.) C 1 e v e. The 

 schematic figure of M. truncata var. semiradiata given by 

 Wolle (Desm. U. S. pi. 38 f. 7) also agrees with the ori- 

 ginal figures; M. truncata in Wittr. & Nordst. exsicc. 

 N:o 373 (collected by W o 1 1 e in North-America!) is likewise 

 the same form. The latter form at least is considerably 

 smaller than the type. (I have measured: length 64— 74— 76, 

 breadth 80—84, isthm. 13— 13 fi). The isthmus is almost 

 half the size. — [N:o 903 c]. — PI. 1 fig. 6. 



In Finland I have observed a form which considerably 

 resembles the variety mentioned above, but it is much 

 larger (length 103—116/0 and it is closely related to the 

 form figured by Printz (Beitr. Norweg. pi. 1 f. 11), which 

 is very large: length 124—128,". 



The whole group of forms, called M. truncata, includes 

 so many different forms, always with continuous series of 

 intermediate forms, that it is not possible to make up a 

 system of them. 



M. crux melitensis (Ehr.) Hass. This species seems 

 to vary far more in Finland than e. g. in England if one is 

 to judge from the Monograph by W est. Besides the var. 



