XANTE IDIUM. 79 



t. 45, f. 2 ; t. 43, f . 10 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 191 ; 



De Toni, Syll. Alg. 1889, p. 918 ; West, Alg. N. Yorks. 1889, p. 293 ; Alg. 



N. Wales, 1890, p. 291 ; Alg. W. Ireland, 1892, p. 164 ; Alg. Engl. Lake 



Distr. 1892, p. 730; Koy & Hiss. Scott, Desm. 1893, p. 244; Nordst. 



Index Desm. 1896, p. 39 ; W. & G. S. West, Alga-fl. Yorks. 1900, p. 68 ; 



Borg. Frcshw. Alg. Faeroes, 1901, p. 229 ; W. & G. S. West, Alg. N. 



Ireland, 1902, p. 31 ; Borge, Beitrage Alg. Schweden, 1906, p. 28. 

 Heterocarpella aculeata Breb. in Cheval, mici'oscop. et xisage, 1839, p. 272. 

 Zygoxanthium aculeatum Kutz. Spec. Alg. 1849, p. 178. 

 DidyiiiidiHm (Xanthidium) aculeatum K-einsch, Algenfl. Frank. 1867, 



p. 129. 

 HolarnnthioH aculeatum Wille in Engler & Prantl, Natiui. Pflanzenfam. 



1890, p. 11. 



Cells of medium size, about as long as broad 

 (without spines), deeply constricted, sinus almost 

 closed at the apex but gradually opening outwards ; 

 semicells elliptic-reniform or elliptic-subsemicircular, 

 apex subtruiicate and often slightly elevated, basal 

 angles sometimes broadly rounded, sometimes rounded- 

 subrectangular ; spines stout, irregular in disposition, 

 not arranged in definite pairs, disposed at or near the 

 margin (in a broad irregular band along the greatest 

 circumference) ; central area a prominent truncate 

 protuberance, sometimes granulated round the margin 

 but often emaroinate and rather irregularly lobecl, 



G2 CD / 



frequently with an emarginate wart or a spine, or 

 both, immediately above the central protuberance. 

 Side view of semicell subcircular, with a prominent 

 truncate protuberance at each side, often with a 

 smaller emarednate wart immediately above it, and 



o / 



with 4-5 spines visible at the apical margin. Vertical 

 view elliptic, with a truncate, granulate or emarginate 

 protuberance at the middle on each side, and with 7 

 or 8 spines showing round each polar margin. Cell- 

 wall punctate or finely scrobiculate. 



Zygospore globose, furnished with numerous long, 

 sharply-pointed spines, each arising from a dilated 

 base. 



Length without spines 64-76 /x, with spines 75 90/x; 

 breadth without spines 62 77 /x, with spines 79-96 //,; 

 breadth of isthmus 19-22*5 ju, ; thickness 35-45 p.; 

 diam. zygosp. without spines 66-70 /*, with spines 

 126-136 *,. 



