88 BRITISH DESMIDIACEJE. 



Dr. Lutkemliller (' Zellmembr. Desm.' 1902) states that the 

 chloroplast in St. inconspicuum is very simple and possesses only 

 one pyrenoid in the middle of the cell (instead of one in each 

 semicell as is often the case in Staurastrum), so that the nucleus 

 is lateral in position. This is a very unusual state of affairs for 

 one of the higher Desrnids. On the other hand, Gay (loc. cit.) 

 figures for St. inconspicuum var. crassum pyrenoids in quite the 

 normal position. 



105. Staurastrum nodosum W. & G. S. West. 



(PL CXLI, fig. 16.) 



St. nodosum West & G. S. West, Alg. S. England, 1897, p. 495, t. 6, f. 23. 



Cells very small, about as long as broad, including the 

 processes, deeply constricted, sinus open with almost 

 straight margins and very acute apex ; semicell s 

 broadly oblong-rectangular, upper angles produced to 

 form short truncate processes, strongly divergent, and 

 with one abrupt constriction, lower angles nearly 

 rectangular, apex of semicell concave ; vertical view 

 triangular, sides concave, processes truncate and 

 biundulate ; cell- wall smooth. 



Zygospore unknown. 



Length, without processes, 11 11 ; with processes, 21 [JL ; 

 breadth, with processes, 19[ji ; breadth of isthmus 5jx. 



ENGLAND. Thursley Common, Surrey ! 



/ *- 



St. nodosum is similar in general appearance to St. incon- 

 spicuum Nordst., but is distinguished by its marked and deep 

 constriction, and by the relatively smaller 'body' in the end 

 view. 



106. Staurastrum brachiatum Ralfs. 

 (PI. CXLI, figs. 14, 15 ; PI. CXLII, figs. 1-7.) 



Staurastrum bifidum Ralfs in Ann. Mag. Nat. Hist. 1845, p. 151, t. 10, f. 3. 

 Goniocystis (Staurastrum} bifida Hass. British Freshw. Alg. 1845, p. 355, 



t. 85, f. 2. 

 Staurastrum bracltiatum Ralfs, Brit. Desm. 1845, p. 131, t. 23, f. 9 ; Arch. 



in Pritch. Inf. 1861, p. 741 ; Rabenh. Krypt. Flor. Sachs. 1863, p. 192 ; 



De Not. Desm. Ital. 1867, p. 54, t. 5, f. 50 ; Rabenh. Flor. Europ. Alg. 



1868, p. 205; Wolle, Desm. U. S. 1884, p. 124, t. 40, f. 37-39; Cooke, 



