PALMELLACEJE 25 



globose, afterwards elongated, or elliptic, sometimes conoid, one 

 or other pole colourless, arranged more or less regularly in longi- 

 tudinal families; tegument thick, at length diffluent, cells 

 dividing in one direction, chiefly at the apex or periphery of the 

 thallus. Propagation by means of agile gonidia. 



Hy drums penicellatus. Ay. Syst. p. 24. 



Thallus rather cartilaginous, olivaceous, of variable thickness, 

 simple and naked below, divided above, and villous with dense 

 fibrils. Internal cells elliptical or somewhat lanceolate ; tegu- 

 ment very thin, scarce visible ; contents homogenous. 



Rabh. Alg. iii. 50. 



Hydrurus fcetidus, Vauch. Kirch. Alg. Schl. p. 106. 



var. e. Ducluzelii. Rabh. Alg. in. 50. 



Thallus from an inch to a foot long, oftentimes sparingly 

 branched, plumose with very dense fibrils. 



SIZE. Cells -006--0095 mm. (Rabh.). 



Hydrurus Diicluzelii, Ag. Cousp. p. 27. Hass. Alg. t. 77, f. 

 3. Rabh. Exs. 176, 873, 1193. 



Batrachospermum myosurus, Ducluz. Conf. Montp. p. 76. 



Palmella myosurus, Lyngb. Hydr. t. 68, E. 



Cluzella myosurus, Bory. Diet. iv. 234. 



In alpine rivulets, on stones, rocks, &c. 



" Root scutate, blackish, hard. Fronds clustered, solid, very gela- 

 tinous, 2-6 inches long or more, 2-4 lines in diameter, freely waving in 

 the water, attenuated towards the apex, branched ; branches scattered, 

 alternate, elongate, slender, beset with other more slender, short raniuii. 

 Gelatinous mass pellucid, viscid, colourless under the microscope, without 

 apparent margin, unless as the granules imbedded within its substance 

 indicate such ; these are globose, green, formed on the stem and primary 

 branches, most densely set in the ramuli, especially towards the margin. 

 Colour of the recent frond brownish-olive, or dark brown, in drying 

 green ; of the granules both recent and dry green." Lyngbye. 



Odour in a recent state very offensive. 



One or other of the many forma of this species has been called 

 Palmodactylon subramosum, Nag., but we have not, as yet, seen any 

 true British representative of that genus. 



Plate X. Jig. 4. #, natural size ; #, portion magnified 400 diam. 



GENUS 18. NEPHROCYTIUM. Nag. (1849.) 

 Cells oblong kidney-shaped, with a dorsal chlorophyllose 

 vesicle, 2-4-8-16 associated in free swimming families sur- 

 rounded by an ample oval or kidney-shaped tegument. Pro- 

 pagation unknown. 



Only two European species, both of which have been found in the 

 British Isles. Both are usually found together, and it is possible that 

 hereafter they may be referred back to one species, as Nageli pro- 

 posed. 



E 



