Freshwater Algae 29 A 



Staurastrutn hexacerum (Ehrenb.) Wittr. 



This species, of which the observed specimens were smaller than usual, 

 was found in small quantities in the lake at Teller, and an imperfect form 

 appeared at Herschel island. 



B^r h c 



Siaurastrum Holmii nov. comb. [Cosmarium Holmii Wille). A, B, Cand D drawings of specimens 

 found by the C. A. E. showing variations in shape from a two-sided form to a four-sided form. 

 E reproduction of Wille's figures; all X 500; a, face view, 6, side view, c, end view. 



Staurastrutn Holmii (Wille) nov. comb. Cosmarium Holmii Wille. 



(Text fig. 5) 



This desmid was first described by Wille in the report of the Dijmphna- 

 Expedition of 1882^. In his description he states: "This species occupies a 

 rather separate position in the genus Cosmarium by its very broad sinus, so that 

 it resembles certain species of Staurastrum. However, were it a Staurastrum, 

 one would expect a tendency to three-cornered shape, but all the specimens I 

 have examined proved to be regular when seen from above, with an equally large 

 swollen place on each side of the semi-cells'.' ' 



The specimens described by Wille have a form intermediate between 

 (1) a form which has no swellings on the sides of the semi-cells and is elliptical 

 in end view like all Cosmaria, and (2) a form in which the swellings have become 

 so large that a typical four-sided Staurastrum is the result (Fig. 5, C). In 

 consideration of this variation from two-sided to four-sided forms, and also in 

 view of the fact that it has a broad sinus, I have come to the conclusion that it 

 is really a Staurastrum and not a Cosmarium. The granulations were well 

 marked in all specimens and differed but slightly in the different forms. 



>Wille, Alger fra Novaia Zemblia og KararHavet, samlede paa Dijmphna Expeditionen, 1882, Copenhagen, 1887. 

 SI am indebted to Mr. F. Johansenfor this translation from the Danish original. 



