ing, than which it is vastly more minute.

Its nearest affinity seems to be

with Anab. impalpabilis of Bory, with which Mr. Thompson contrasts it; but that is described as forming on the paper on which it is dried, a glossy verdigris-green stain, while ours in this state is dull green and wholly without gloss. For an interesting account of its various changes &c., see Mr. Thompson's paper in the 5th vol. of the 'Annals of Natural History.'

CI. ECHINELLA. Ach.

Exceedingly minute, dot-like, sphærical fronds, composed of jointed filaments radiating from a centre. Name, Echinus, the hedgehog; in allusion to the bristly appearance of the radiating particles.

1. E. articulata, Ag.; glaucous ; filaments jointed, spreading every way from a centre, and forming a globe. Sm.Harv. in Hook. Br. Fl. ii. p. 398.

In a lake in Anglesea, Rev. H. Davies. Fronds exceedingly minute, covering the surface of the water in June and July, with a thin, glaucousgreen scum. Under the microscope this is found to be made up of sphærical bodies, composed of jointed, straight filaments, of equal length, radiating in all directions from the centre.

CII. EUTOMIA. Nov. Gen.

Exceedingly minute, dot-like, flat fronds, composed of two cloven lamina cohering by the edges, and finally separating. -Name, Ev, well, and TEuvw, to cut; the frustules being elegantly cloven in a radiating manner. This genus is proposed for Echinella radiosa of Lyngb., together with the two following species; none of which can be included in Echinella, either as defined by Agardh, or as above; but in what part of the system to place them I confess myself at a loss to decide. To the Diatomacea they bear a very close affinity, but among them present the anomalous feature of dichotomously-cloven frustules. The nearest approach to such a structure is in Desmidium, and perhaps they might be placed in DESMIDIEÆ, as related in the same manner to that genus as Styllaria, Frustulia, and Cymbella are to the more compound genera in their respective tribes. I need hardly add that their relationship to the animal kingdom is almost as strong as to the vegetable.

1. E. rotata; "frond plane, circular, divided by a line. passing through the centre, each portion composed of radiating segments cleft nearly to the central line." Grev.-Echi

188

EUTOMIA-BYSSOCLADIUM-MYCINEMA.

nella rotata, Grev. in Hook. Br. Fl. ii. p. 398. E. radiosa, Carm. MSS. (not of Lyngb.)

In fresh water, among Conferve and aquatic mosses. Appin, Capt. Carmichael. Near Dolgelly, Mr. Ralfs.-"Minute, scattered, bright transparent green." Grev.-Of Carmichael's plant I have seen no specimens, and therefore think it better to retain Dr. Greville's description, adding the following, taken from Mr. Ralfs's. - Fronds plane, circular or sub-elliptical, composed of two semicircular frustules cohering by their chords and finally separating. Each deeply five-lobed; the central lobe narrowest and simply emarginate; the lateral ones deeply bifid, with the apices of their segments crenulate. Colour a bright yellow-green, colourless at the edges.

2. E. oblonga; "frond compressed, oblong, crenato-pinnatifid and lobed, divided transversely in the middle almost to the centre." Grev.-Echinella oblonga, Grev. in Hook. 1. c. p. 398.

With the last, at Appin, Capt. Carmichael.-Pale transparent green. These are animals, instead of plants, if the faculty of locomotion will entitle them to that rank. Carm. MSS.

TRIBE 22.? BYSSOIDEÆ.*

CIII. BYSSOCLADIUM. Ag.

Filaments cobwebby, issuing from a centre, with scattered, external granules. Name, Burgos, a kind of fungus, and unados, a branch.

1. B. fenestrale, Ag. Syst. p. 31; Harv. l. c. p. 379. Conferva fenestralis, Dillw. t. 94.

On windows and damp glass, on which it forms roundish, dirty white spots.

CIV. MYCINEMA. Ag.

Filaments membranaceous, opaque, tenacious, coloured. -Name, μuns, a fungus, and vua, a thread. Decumbent, cobwebby plants, growing on rotten wood; probably only imperfect fungi.

1. M. arachnoideum, Ag.; filaments branched, slender, pale yellow, laxly interwoven into a cobwebby membrane; branches scattered, remote, simple; articulations variable, about four times as long as broad. Harv. l. c. p. 379. Conf. arachnoidea, Dillw. t. C.

On rotten wood.

2. M. fulvum, Ag.; filaments decumbent, elongate, mem* Probably imperfect Fungi.

branaceous, equal, branched, loosely interwoven into a soft, expanded, tawny stratum; articulations thrice as long as broad. Harv. l. c. p. 379; Loud. Encycl. Pl. No. 15061. On dead trees; but I do not know where found.

3. M. rubiginosum, Ag.; filaments much branched, rigid, sub-erect, reddish, interwoven into a sub-solid mass; articulations about four times as long as broad. Harv. l. c. p. 380. Conf. rubiginosa, Dillw. t. 68.

On rotten wood, Dillw.

4. M. phosphorea, Ag.; filaments branched, ascending, very short, violet-blue, densely interwoven into an uniform crust; articulations once and a half as long as broad. Harv. 1. c. p. 389. Conf. phosphorea, Dillw. t. 88. Auricularia phosphorea, Sow. Fung. t. 350.

On decaying wood.

CV. CHROOLEPUS. Ag.

Filaments rigid, sub-solid, opaque, falling to powder, erect, minute; joints often contracted.-Name, xpoos, the skin, and AETW, to decorticate; from the change which the filaments undergo. Small as this genus is it contains two distinct tribes; the first, or legitimate Chroolepus, is intermediate between Mycinema and Protonema; the second includes some minute objects which ought surely to be removed to the byssoid fungi, perhaps to the genera Monilia or Helmisporium. Dr. Walker Arnott, indeed, is of opinion with Fries, that the whole should form the modified genus Byssus, and be removed from the Algæ.

1. Orange, red, or yellow, rarely greenish, (Amphiconium, Spr.)

1. C. aureus, Harv. ; filaments forming soft, cushion-like tufts, flexuous, irregularly branched, yellow-green or orange; articulations twice as long as broad. Harv. in Hook. Br. Fl. ii. p. 380. Conferva aurea, Dillw. t. 35. Byssus aurea, E. Bot. t. 212. Trentepohlia aurea, Ag. Syst. p. 36. Ectocarpus aureus, Lyngb. t. 44. Amphiconium aureum, Spr. Conferva ilicicola, E. Bot. t. 1639.

On rocks and trees, very common. This forms beautiful velvetty cushions, of a chlorous, orange, or brick-red colour, fading, after long keeping in the herbarium, to a dull ash-grey.

2. C. Jolithus, Ag.; filaments tufted, erect, very short,

orange-red, dichotomous; articulations once and a half as long as broad. Harv. l. c. p. 380.

On rocks in woods &c.- Dr. Arnott suggests that this is merely a state of the preceding. I fully agree with him, and would willingly add the two following also, as mere varieties depending on habitat.

3. C. odoratus, Ag.; filaments branched, tufted, short, erect, fulvous; branches patent, rigid; articulations as long as broad. Harv. l. c. p. 380. Amphiconium Linnæi, Spr. Johnst. Berw. Fl. ii. p. 245.

On the bark of ash trees. About Berwick, Dr. Johnston.

4. C. lichenicolus, Ag.; tufts red-orange; filaments erect, tufted, alternately branched, rigid; articulations slightly tumid, as long as broad. Harv. l. c. p. 381. Conf. lichenicola, E. Bot. t. 1609.

On lichens and old trees, not uncommon.

2. Black, torulose; bearing club-shaped bodies resembling sporidia,

(Helmisporium ?)

5. C. ebenea, Ag. ; filaments branched, erect, tufted, rigid, sub-cartilaginous, black, obtuse; articulations as long as broad. Harv. l. c. p. 381. Conf. ebenea, Dillw. t. 101.

Byssus nigra, E. Bot. t. 702.

On rocks and trees in alpine districts, frequent." Tufts of indefinite extent, velvetty black. Filaments scarcely more than a line (or two) in length, interwoven, slightly branched, extremely fragile. Articulations about as broad as long, rather translucent. I have found specimens of this plant bearing pod-shaped branches or appendages, thicker than the main filament, with the articulations twice as broad as long, and readily separating into single joints." Carm. MSS.-These pod-shaped appendages are surely of the same nature as what are called "sporidia" in the genus Helmisporium of Link; to which genus the black species of Chroolepus ought, perhaps, to be removed.

6. C. melanus, Carm.; filaments slightly branched, erect, forming a jet-black stratum; articulations oval, twice as long as broad; joints contracted. Harv. l. c. p. 381. Syncollesia? melana, Ag. Syst. p. 32. Conf. melana, Lyngb. t. 57.

On old beech trees at Appin, Capt. Carmichael.-" Stratum several inches in diameter, of a deep, velvetty black colour. Filaments about a line in length, slightly branched, exceedingly fragile; articulations about twice as long as broad, oval, moniliform, subdiaphanous." Carm. MS.-Lyngbye's figure, though rude, is very characteristic. I do not see how this differs from Monilia attenuata (Grev. Crypt. t. 255) except in being branched.

7. C. mesomelas, Carm. ; filaments slightly branched, erect, forming a jet-black stratum; articulations globose, opaque, the uppermost pellucid. Carm.—Harv. l. c. p. 381.

On decaying stems of Urtica dioica, Capt. Carmichael.-" Stratum half an inch in length, of a deep black colour. Filaments erect, slightly branched; branches divaricate at the base, ascending. Articulations globular, moniliform, perfectly opaque, with the exception of one or two of the terminal ones. Siliquæform appendages scattered, as in C. ebenea." Carm. MSS.

8. C. Arnottii, Hook.; filaments very short, heaped together, fragile, moniliform, slightly branched; branches simple, subulate, spine-like, divaricate; articulations rather shorter than broad; joints contracted. Harv. l. c. p. 381.

On yews, at Cleish Castle, Kinrosshire, Dr. Walker Arnott, of Arlary."This singular plant resembles none other that I know. It is found only on yew-trees: these are of great age, and have, in general, near the root, a very irregular outline, exhibiting deep cracks or clefts: from these fissures exudes the juice of the tree; this soon afterwards thickens and becomes covered with a soft filamentous substance, that might be mistaken for Racodium cellare, or rather R. vulgare, Fries, if indeed it has not been frequently passed over for that plant. Such is its first state. The sap of the tree continues to flow through the plant, which also increases in size and thickness, at last becoming a firm, corky, almost hemisphærical substance, losing nearly all trace of the filamentous surface, and slightly resembling specimens of Sphæria deusta; presenting like them, when broken, though generally very indistinctly, the appearance of concentric layers, which, from the observations I have made, mark pretty nearly the number of years the specimen has been in forming. This I have no doubt is caused by the inspissation, at the close of each season, of the sap of the tree absorbed by the parasite. I may add, that when well dried, this species takes fire very readily from a spark, and burns like tinder." Arn. in litt.

CVI. PROTONEMA. Ag.

Filaments sub-articulated, branched, rooting, mostly green. -Name, πρоτos, first, and nua, a thread. The following obscure productions are probably rudimentary mosses. P. velutinum, Ag. (the well-known Byssus velutina), having been proved to be merely the commencement of Polytrichum aloides, I have omitted.

1. P. umbrosum, Ag.; stratum velvetty green; filaments erect, obtuse, fastigiate, fragile; articulations gibbous. Ag. Syst. p. 43; Harv. l. c. p. 383. Conf. umbrosa, Dillw. t. 61. On damp ground.

2. P. cryptarum, Ag.; filaments dichotomous, green; branches divaricating, acuminate; articulations thrice as long as broad. Harv. 1. c. p. 383. Conf. cryptarum, Dillw. t. E; E. Bot. t. 2588.

In caves; first discovered by R. Brown, Esq.- Agardh suspects this to be the young of some Phascum.