PENIUM. 77 



SCOTLAND. Near Balallan, Lewis ; and near Tarbert, 

 Harris, Outer Hebrides ! 



Si i fur as our own experience goes, tliis variety is confined 

 to the extreme north-west of Scotland. 



Var. inflatum var. nor. (PL VII, fig. 18.) 



Somewhat larger than the typical form, 3 times 

 longer than the diameter, elliptic-fusiform, in the 

 median part of the cell subcylindrical ; apices rounded. 



Length 74 /t; breadth 24 /t. 



SCOTLAND. Ben Laoigh, Perthshire ! 



This variety is of the same outward form as the small forms of 

 P. Naricnla figured by Heimerl (Desm. alp. 1891, p. 590, t. 5, 

 f. 2.) and erroneously ascribed by him to Wille's "forma 

 apicibus rotundato-truncntis " (= forma Willei Schmidle). It 

 also bears a great resemblance to another plant described by 

 Heimerl (1. c. t. 5, f. 3) as P. cloxtt mi tie* Ralfs, forma minor, 

 but it is relatively shorter and of smaller size. Schmidle has 

 termed this second form of HeimeiTs P. Heimerlian nm (consult 

 Schmidle, Alg. Bern. Alp. 1894, p. 89), but it is very difficult 

 to define as a species distinct from P. Navicula and P. Libel- 

 Inla var. intermedium. 



3. Penium Jenneri Ralfs. 

 (PL VII, figs. 20, 21.) 



I'enium Jenneri Ralfs, Brit. Desm. 1848, p. 153, t. 33, f. 2- Eabenh. Flor. 



Europ. Algar. Ill, 1868, p. 120; Wittr. Gotl. Ol. sotv. Alg. 1872, p. (>7 ; 



G-ay, Monogr. loc. Conj. 188-4, p. 69 ; Wolle, Desm. TLS. 1884, p. :;ii : 



Eacib. Desm. Nowe, 1889, p. 74; Xurdst. Index Desmid. 1896, p. 1 .">(; 



West, Alg. W. Ireland, 1892, p. li's. 



Penium Brebissonii var. Jenneri Kirchn. Alg. Sollies. 1878, p. 136. 

 Cylindrocystis Brebissonii var. Jenneri Hansg. Prodr. Algenfl. Bomh. 1888, 



p. 175. ' 



Cells small, 2-4 times longer than their diameter, 

 unconstricted, cylindrical ; apices broadly rounded ; 

 cell-wall smooth ; chloroplasts axile. 



Zygospore globose and smooth, becoming yellow- 

 brown. 



Length 20-58 ^t; breadth 13-15^; diameter of 

 zygospore 25-35 /u. 



