_Explanation of Terms.
Before going farther, it seems proper to explain, in a general way, a very few terms, chiefly connected with the fructification of the fuci, as these terms must frequently recur in the subsequent part of this article, and are scarce ly to be found explained in elementary books, as applicable to this class of _plants.
By a receptacle is meant a process, often resembling a pod, and generally containing many tubercles, which again contain the seeds, as in Claudea elegans, (Plate CCLXI. Fig. 3.) ; F. vesiculosus, Fig. 4. ; and F. nodosus, Fig 5. at a a a.
Tubercles are nearly solid, generally roundish, often composed of minute fibres, among which the seeds lie ; they frequently resemble pimples or warts, and arc often perforated, or marked with a pore ; frequently clustered together; sometimes half immersed in the frond ; some times on short peduncles. See Plate CCLXI. Figs. 3, 4, 5, above referred to ; and also Fig.7.
Capsules are seed-veesels, often partly hollow ; fre quently placed singly ; smooth on the surface; sometimes spherical, but often of a lanceolate shape, like minute sili qux. Sec Plate CCLXI. Fig. 10. spherical capsules ; Fig. 11. lanceolate capsules. In some cases, it may be observ ed, the terms tubercle and capsule become nearly synony mous : they seem to be used almost promisculously by Mr Turner, in speaking of particular species, as F. bractea tus, gigartinus, and kaliformis, (Turn. t. 25, 28, 29.) resides are the air-bladders, well known in F. vesiculo sus, Plate CCLXI. Fig. 4. b; and nodosus, Fig. 5. b, and others; but these vcsic2tlx have no connection with the fructification.
Previous to the account of Larnourotx's system, it may be right to notice very shortly some of the methods sug gested since the time of Linnaeus and Gmclin, particularly those of Walker, Stackhouse Roth, Decandollc, and Walt lenberg.
Dr Walker's Method.
The method of Dr John Walker, late professor of natu ral history in the university of Edinburgh, was never pub lished; but it has been kindly communicated by his friend Mr Charles Stewart (author of Elements of Natural His tory, in 2 vols. 8vo. 1801, and editor of the new edition of
Dillenius's Historia Illuscorum), as contained in vol. 6th of the Doctor's Advetsaria, dated 1771. We trust that we do an acceptable service to botanists in here preserving it. Not that it is preferable to some later methods, but that it constitutes matter of some curiosity, and enables us to trace the progress of the science. It has besides been indirect ly alluded to by Mr Turner, in his Historia Fucoruuz, vol.
p. 96.
Dr Walker divides the submersed algx into fourteen genera: Cervina, Flabellaria, Bombycina, Annularia, No dularia, Catenaria, Focus, Platyceros, Phasganon, Ulva, Chartacea, Plumarium, Neurophyllum, and Spongia. Of these we shall give a very brief account, stating only the essential character, and the description of the fructification ; and we think that fairness requires that characters and de scriptions be given in his own words.
The 1st genus Ccrvina or Hornwecd, has the following character: 64 Coriacea, dichotoma, inarticulata. Fr. Vesi eulm terminales vel superficiales, sessiles." It is divided into two sections; compressed, as litmus nodosus, and round, as F. fastigiatus, Lin. (rotundus, Turn. t. 5.) By vesiculx, it is scarcely necessary to remark, the author means receptacles : He uses bulbs to express air-vesicles.
2d genus, Flabellaria or Fanweed : Coriacea, pcnnata, inarticulata. Fr. Vcsiculx rotundatx terminales." It is likewise divided into two sections ; with air-bladders, as F. siliquosus (Turn. t. 159); and without air-bladders, as F. pinnatifidus, (t. 20.) 3d, Bombycina or Silkweed : Cartilaginea abulla, imar ticulata, ramis filamentosis. Fr. Vesicular globosa., ramis solidis." This includes Conferva. scoparia, C. tomen tosa, and similar plants.
4th, Annularia or Ringweed : uCartilaginea annulata, ramis filamentosis. Fr. Tubercular globosa. solidae termi pales." This is subdivided into several sections, and em braces a number of Confervx, as C. fucoides and pennata of Hudson.