464 Mr. J. Ralfs on the British species of (jomphonema. 



leaves of aquatic plants in Tr^gwainton ponds near Penzance, 

 where it grows with Gomph. minutum, which to the naked eye 

 much resembles it ; but the present is a taller plant, although its 

 frustules are considerably less. 



The stipes is slender, much-branched ; the frustules minute, 

 narrow, often nearly linear, the terminal puncta very minute ; 

 lateral surfaces narrow-lanceolate, striated. 



The frustules somewhat resemble those of Gomph. Berkeleii, 

 but they are more elongated, much narrower, often nearly linear, 

 and their puncta are far less distinct ; the lateral view is also more 

 slender, and lanceolate not clavate. 



Plate XVIII. fig. 7. Gojnphonema dichotomum. 



6. G. Berkeleii, Grev., forms rather large mucous masses; stipes 

 branched, entangled ; frustules short, triangular, with two conspi- 

 cuous puncta at the end ; lateral surfaces obovate or subclavate, 

 striated. Grev. in Hook. Br. Fl. vol. ii. p. 409 ; Harv. Br. Alg. 

 p. 207. Gomph.} oUvacea, Eh. Die Infus. p. 218. t. 18. f . 9 r 

 Pritch. Infus. p. 228. Exilaria minutissima, Berk. Br. Alg. p. 22. 

 t. 7. f. 1. Meridion vernale, Ag. Consp. Diatom, p. 39. Frustulia 

 olivacea, Kutz. Syn. Diatom, p. 556. f, 31. Gomph. geminatum, 

 Kutz. Alg. aq. dulc. No. 13. Gomph. Leibleini, Kutz. Synop. 

 Diatom, p. 568. fig. 46. 

 j3. scattered, frustules more firmly attached to the stipes, which can 

 be detected without difificulty. 



On stones, &c. in fresh water: spring. King's ClifFe, Northampton- 

 shire, Rev. M.J.Berkeley; Henfield, Sussex, Mr. Borrer; Mayfield, 

 Sussex, Mr. Jenner ; Yarmouth, Mr. Dawson Turner (according to a 

 specimen from Mr. Borrer) ; river Severn near Shrewsbury, Mr. 

 Leighton ; Cheshunt, Herts, and river Lea, Mr. A. H. Hassall. At 

 the base of Bandon mountains, Mr. Andrews. 

 /3. Duddingston Loch, Dr. Greville. 



This plant, which forms rather large mucous masses, is of a pale 

 hyaline brown, but when dried generally becomes of a pale green 

 with a granulated appearance. The stipes is hyaline and more 

 or less branched; frustules minute, short, triangular, easily de- 

 tached from the stipes ; puncta at the end strongly marked ; la- 

 teral surfaces striated, obovate in the shorter frustules, somewhat 

 clavate in the longer ones. 



In general the frustules are easily detached from their stipes, 

 and as the latter are with difficulty distinguished from the gela- 

 tinous substance in which they are imbedded, they are very liable 

 to be overlooked, whence the plant has often been referred to an- 

 other genus. 



In the spring of 1841, 1 applied to Mr. Borrer for information 

 respecting Meridion vernale, which Agardh in his ' Conspectus 

 Criticus Diatomacearum ' mentions as a British plant upon the 

 authority of a specimen received from Mr. Borrer, but which is 



