402 ALGM DIATOMACEJE. [Fragilaria. 



verted into a series of circular globules. — M. nummuloides, Ag. 

 Syst. Alg. p. 8 ? — Conferva nummuloides, E. Bot. t. 2287, (not 

 of Dillwyn). 



Parasitic on Conferva and other filiform marine Alga. Shoreham 

 harbour and at Southwick, Mr. Borrer. March. — The filaments of the 

 preceding species are brownish-yellow, those of the present of a 

 grayish-green colour. This is quoted doubtfully by Agardh, under his 

 M. nummuloides, of which I do not possess a specimen. The filaments 

 of Mr. Borrer's plant are short, somewhat tortuous, and beautifully 

 moniliform. 



3. M. linedta, Ag. {striated Meloseira); filaments fragile con- 

 tracted at the articulations, transversely striated with one or two 

 fine lines, the joints 2 — 3 times longer than they are broad. — Ag. 

 Syst. Alg. p. 8. — Fragilaria lineata, Lyngb. Hydroph. Dan. 

 p. 184. t. 63 Conferva lineata, Dillw. Conf. p. 44. U B. 



Streams and ditches containing brackish water. In the river Lea, at 

 Walthamstow, Mr. Dillwyn.— According to Lyngbye, the filaments form 

 dense tufts, two or three inches long, exceedingly fragile, and pulveru- 

 lent when dry. Mr. Dillwyn found only a single specimen. 



99. Desmidium. Ag. Desmidium. 

 Frustula forming simple, angular, pseudo-articulated fila)7ients, 

 hyaline at the crenate edges, at length separating. — Name ; 

 hrpog, a bond; from the union of the filaments. 



1. D. Swdrtzii, Ag. (Swartzian Desmidium); filaments trian- 

 gular, the angles of the joints bicrenate — Ag. Syst. Alg. p. 9. 

 Grev. Crypt. Fl. t. 292. — Diatoma Swartzii, Ag. Syst. Alg. 

 p. 34. Lyngb. Hydroph. Dan. p. 177. t. 61. 



Shallow pools and ditches. Appiir, Capt. Carmichael. — Filaments of a 

 fine green, an inch or more in length, flexuose, simple, the angles pellu- 

 cid and colourless. Before the ultimate separation of the joints, the 

 whole has a curious pinnatifid appearance. 



2. D. cylindricum, Grev. (cylindrical Desmidium); filaments 

 cylindrical two-angled, the angles of the joints bicrenate. Grev. 

 Crypt. Fl. t. 293. 



Shallow pools and ditches. Appin, Capt. Carmichael. Spring. — 

 Very similar to the preceding ; but, under the microscope, the charac- 

 ters above given distinguish it at once. 



Tribe XXIII. Fragilarieje. 

 Filaments plane, extremely fragile, composed of rectilinear frus- 

 tula. (Frustula sometimes apparently radiating from a centre and 

 not presenting the appearance of a filament.) 



100. Fragilaria. Lyngb. Fragilaria. 

 Frustida forming plane, pseudo -articulated, densely striated, 



