1 68 ANNALS OF SCOTTISH NATURAL HISTORY 



end view oval. Surface smooth, not punctate. Isthmus 

 about one-third of the breadth of the semi-cell. Zygospore 

 thick-walled, very dark brown, almost black ; perfectly smooth 

 and globular. Long., 15-17 ^ ; lat., 15-17 /x ; crass., 7-8 ^ ; 

 isth., 5 /x; dia. of zygospore 23-25 p. (Our Plate I. fig. 14.) 

 Very generally distributed. 



This simple-looking, but very distinct, species was de- 

 tected by Mr. Archer, in Ireland, many years ago. It con- 

 jugates abundantly, sometimes in profusion, and may be 

 readily recognised by the smooth, globular, very dark 

 zygospore. 



88. C. Meneghinii, Breb. Abundant. Most of the so-called varieties 

 of this species occur abundantly. But surely the form to 

 which De Bary affixes this name is a very different thing 

 from that of De Brebisson as limited and figured by Ralfs ; 

 while again, both are quite different from the var. (3 simplid- 

 nniin of Wille. It is much to be wished that the zygospores 

 of all these forms could be found and published. 



89. C. microsphinctiiin, Wittr. and Nord. Very rare. Aberdeen 



Ardtannes near Inverurie, Craigendinnie near Aboyne, and 

 Presswhin in Cromar. 



Var. majtis, n. var. Differs from the ordinary form 

 in being double the size. Long., So //,; lat., 52 //. ; 

 isth., 35 //. (Our Plate I. fig. 7.) Extremely rare. 

 Aberdeen Presswhin in Cromar, with the type. 

 Var. parvula, Wille. Very rare. Fife Kemback 

 near St. Andrews (Mrs. Farquharson). 



90. C. moniliforme (Turp.), Ralfs. Not uncommon. Sutherland, 



Ross, Inverness, Aberdeen, Kincardine, Forfar, Perth, 

 Argyle. One form of this species has a distinct isthmus, 

 connecting the semi-cells ; its zygospore (found in a small 

 pool north of Loch Dawin, Aberdeen) is globular, smooth, 

 and twice the size of a semi-cell. 



Forma elliptica, Nord. ("Sydl. Norg. Desm.," 1873, 

 p. 22), is probably the same as our species C. 

 Jacobsenii (Jacobsen's " Desmid. du Danemark," 

 p. 200, Tab. VIII. fig. 24, under the name of C. 

 moniliferum). Now, while granting this, we can 

 scarcely admit that these are merely two forms of 

 one species. While bearing a certain resemblance, 

 each holds constantly to its special character- 

 istics : the semi-cells of moniliforme are globular 

 from all points of view, while those of Jacobsenii 

 are transversely oval in front view, circular in 

 side view, and oval in end view ; besides, the 



