STAURASTRUM. 1 65 



155. Staurastrum Heimerlianum Liitkem. 

 (PL CXLIX, figs. 14, 15.) 



Staurastrum cruciatum Heimerl, Desm. alp. 1891, p. 608, t. 5, f." 24. 

 -St. Heimerlianum Liitkem. Desm. Attersees, 1893, p. 568 ; West & G. S. 

 West. Alga-fl. Yorks. 1902, p. 105 ; Borge, Beitr. Alg. Schweden, 1906, 

 p. 46, t. 3, f. 38. 



Cells small, lf-2 times broader than long, deeply con- 

 stricted, sinus acute-angled, widening towards the 

 exterior ; semicells narrowly fusiform, dorsal margin 



I O 



less convex than the ventral, gradually attenuated 

 towards the poles to form long, parallel or slightly con- 

 verging processes, which have truncate apices and end 

 with 2 or 3 short spines ; upper margin of process 

 bearing a few stout spines, projecting almost perpen- 

 dicularly ; the lower margin usually with 2 ; spines 

 unequal in length. Vertical view usually quadrangular 

 (sometimes triangular), sides slightly concave, angles 

 produced to form stout processes, with 2 or 3 irregular 

 series of spines. 



Zygospore subglobose, somewhat angular, bearing 

 irregular spines 1-3 times dichotomous at the apex. 



Length 17-26(ji ; breadth, including processes, 29*4- 

 38 \L ; breadth of isthmus 6-8 t u. ; length of spines 1-4 pi ; 

 diam. zygosp., without appendages, 20-26 \L \ with 

 appendages, about 42 pi . 



ENGLAND. Cam Fell. W. Yorks ! 



Geogr. Distribution. Germany. Austria. Sweden 

 (var.). 



Var. spinulosum Liitkem. (PI. CXLIX, fig. 16.) 



*S7. Heimerlianum var. spinulosum Liitkem. Desm. Attersees, 1893, p. 568, 

 t. 9, f. 17 ; Roy & Biss. Scott, Desm. 1893, p. 21 ; West & G. S. West, 

 Alg. S. England, 1897, p. 495. 



Cells provided with regular series of spines, equal in 

 length, arranged in concentric series round the angles 

 and forming longitudinal rows in the front view ; centre of 

 apex smooth. 



Length 21-26 pi ; breadth, including processes, 27-33 pi; 

 breadth of isthmus 9 pi ; length of spines about 2 pi. 



