68 BRITISH DESMIDIAC'E.E. 



occurring mixed with the typical plants. It is readily dis- 

 tinguished from the typical form by its small size and exactly 

 cylindrical cells, which are not attenuated towards the apices. 



4. Netrium interruption (Breb) Liitkem. 

 (PI. VII, figs. 1, 2.) 



Penium intemiptum Breb. in Ealfs' Brit. Desm. 1848, p. 151, t. 25, f. 4 ; 

 De Bary, Conj. 1858, p. 42-44, 46, 73, t. 5, f. 1-4 ; Arch, in Pritch. 

 Infus. 1861, p. 751, t. 3, f. 45; Eabenh. Flor. Europ. Algar. 1868, III, 

 p. 119 ; Delp. Desm. subalp. 1877, p. 79, t. 15, f. 1-9 ; Wolle, Desm. 

 U.S. 1884, p. 35, t, 5, f. 14, 15 ; Cooke, Brit. Desm. 1886, p. 41, t. 16. 

 f . 2 ; Hauptfl. Zellm. u. Hiillgallerte Desm. 1888, p. 101, t. 3, f. 61 ; 

 West, Alg. W. Ireland, 1892, p. 127 ; Roy & Biss. Scott. Desm. 1894, 

 p. 59 (sep.) ; Nordst. Index Desmicl. 1896, p. 148 ; West & G. S. West, 

 Alg. S. England, 1897, p. 479 ; Alga-fl. Yorks. 1900, p. 45 ; Alg. N. 

 Ireland, 1902, p. 21, 



Closterium (Netrium) interruption Beinsch, Algenfl. Frank. 1867, p. 185. 



Netrium in'erruptum (Breb.) Liitkem. Zellmembr. Desmid. 1902, p. 407. 



Cells large, 4-6 times longer than their diameter, not 

 constricted, cylindrical, near each extremity becoming 

 suddenly conical, apices obtusely rounded ; chloro- 

 plasts four, two in each semicell, median ones cylin- 

 drical, apical ones conical, each chloroplast with about 

 eight longitudinal plates, free margins of plates entire ; 

 apical vacuole conspicuous and containing a solitary 

 moving- granule. 



o O 



Zygospore unknown. 



Length 220-320 p; breadth 37-64 /i. 



ENGLAND. Cumberland ! Westmoreland ! N. Yorks ! 

 Lancashire! Cheshire (Roij). Warwick (Wills). Sussex 

 (B.ct1fs). Surrey! Hants (Eoij}. Cornwall! (Ealfs). 



WALES. Capel Curig! (CooJce ^ Wills), Llyn Idwal, 

 Llyn-y-cwm-ffynon, and near Dolbadarn Castle, Car- 

 narvonshire ! 



SCOTLAND. Ross, Inverness ! , Aberdeen, Kincardine, 

 Forfar, Perth! (Roy cj- Bissctt). Lewis, Outer 

 Hebrides ! 



IRELAND. Near Westport, Mayo ! Loughs Creggan 

 and Aunierin, Galway ! Dublin and Wicklow (Archer). 

 Slieve Donard, Down ! 



Geogr. Distribution-.- -France. Germany. Austria. 



