122 YORKSHIRE NAtURALlSTs' UNION. 



Var. duplex (Kiitz.). [Syn. R. duplex Kiitz.; R. poly- 

 morphum var. sigmoidetim Rabenh.J. 

 S.W.— CuUingworth. 

 Mid W.— Moor-AUerton; Roundhay (W. B. Turner). Baildon. 



Var, spirale West & G. S. West. 

 Mid W. — Hawksworth, in immense quantities amongst Myrio- 

 phylliim spicatum. Harrogate. 

 N.E. — Pilmoor, near Thirsk. 



582. Rhaphidium setigerum (Schroder) Nob. 



[Syn. Reinschiella 1 setigera Schroder]. 



N.E. — Near Rievaulx Abbey. 



The plants we observed agreed well with the description and 

 figures given by Schroder ('Ueber das Plankton der Oder,' 

 Bericht. Deutsch. Botan. Gesellsch., 1897, Bd. xv., Heft 9, p. 

 492, t. XXV., f. 4) except that the setre were a little shorter. 



Length with setse 75 — 88ju.; without setfe 29 — 31 fi; breadth 



57— 6'S/*- 



Quite recently Lemmermann has described a plant under the 

 name of Closteriopsis longissima which is very closely allied to 

 R. setigerum (Cfr. Ploner Forschungsberichten, Teil 7, p. 29, 

 t. ii., f. 36-38). He places it in the DesmidieEe between Clos- 

 terium and Pleurotcenium, but in this he is quite wrong, as 

 Closteriopsis is not a Desmid. 



In the same paper Lemmermann places R. polymorphum var. 

 mirabile West & G. S. West as a distinct species — R. mirabile 

 Lemmerm. In this also he is quite wrong, as R. polymorphum 

 var. mirabile occurred amongst hundreds of specimens of all 

 forms of R. polymorphum and therefore could only be described 

 as a peculiar form of it. 



Species of Rhaphidium, Scenedesinus, and Dactylococcus very 

 often (many of them as a rule) possess pyrenoids. 



Raphidiym setigerum has not been previously recorded for 

 the British Isles. 



583. Rhaphidium convolutum (Corda) Rabenh. 

 S.W.— Denholme. 



Trans. Y.X.U., 1S99 (pub. July 1901). Bol. Scries, Vol. 5. 



