Volume 1

The nature-printed British sea-weeds : a history, accompanied by figures and dissections of the algae of the British Isles / by William Grosart Johnstone and Alexander Croall ; nature-printed by Henry Bradbury.

Date:
1859-1860
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    No text description is available for this image
    Plate II. EHODOMELA SUBFUSCA.—Ag. Gen. Char. — Frond filiform, solid, inarticulate, the axis composed of oblong hyaline cells, the periphery of minute, irregular, coloured cellules. Fructification : 1. Ovate capsules (ceramidia) containing a tuft of pear-shaped spores ; 2. Petra- spores immersed in swollenramuli, “ or contained in proper pod-like receptacles,” placed in a double row. Name from podeos, “red,” and fxe\as, “black,” referring to the colour of the plant. Rhodomela subfusca.—Frond filiform, much and irregularly branched; branches somewhat flexuose, more regularly distichous and pinnated upwards; ultimate divisions generally regularly pinnated, with subulate pinnules; capsules placed obliquely on short stalks. Rhodomela subfusca.—Ag. Sp. Alg. vol. i. p. 378 ; Ag. Syst. p. 199 ; Sprang. Syst. Veg. vol. iv. p. 343 ; Grcv. Alg. Brit. p. 193 ; HooJc. Br. FI. vol. ii. p. 294; Wyatt, Alg. Danm. No. Ill; Ilarv. in Mack. FI. Ilib. part 3, p. 197; Ilarv. Man. p. 79 ; Ilarv. P. B. plate 264 ; Ilarv. N.B. A. part 2, p. 26 ; Ilarv. Syn. p. 64; Atlas, pi. 24, fig. 103; Fncll. 3rd Suppl. p. 47. Lophtjra cymosa.—Kiitz. Phyc. Gen. p. 435. Gigartina subfusca.— Lamour. Ess. p. 48 ; Lyngb. Hyd. Ban. p. 47, t. 10 ; Grcv. FI. Edin. p. 289. Sphairococcus subfuscus.—Hook. FI. Scot, part 2, p. 104. Fucus subfuscus. — Woodw. in Linn. Trans, vol. i. p. 131, t. 12 ; Good. <fc Woodw. Linn. Trans, vol. iii. p. 212 ; Turn. Syn. Fuc. p. 350; Turn. Hist. t. 10; E. Bot. t. 1164; Esper, Ic. Fuc. vol. ii. p. 11, t. 117. Fucus confervoides.—Huds. FI. Ang. p. 591. Fucus variabilis.—Good. 6a Woodw. Linn. Trans, vol. iii. p. 220. Fucus setaceus.— Widf. Crypt. Aquat. No. 40. Had.—In the sea, on rocks, shells, and Algae. Perennial. Summer. Common. Geogr. Dist.—Atlantic shores of Europe and North America. Description.—Root, a small flat disc. Fronds much tufted, three to twelve inches long, scarcely half a line in diameter, filiform, from a somewhat contracted cylindrical base, expanding slightly upwards. Stem about half an inch to an inch and a-half long, much and irregularly branched upwards, and everywhere more or less beset with the setaceous remains of the old branches; four or five, or, in luxuriant specimens, even six or seven times divided; the branching becoming more and more
    regular upwards, the ultimate and young branchlets being beautifully plumose, with regular alternate pinnules. Capsules not uncommon, in summer, on the pinnules, ovate, on short somewhat oblique stalks. Tetraspores also abundant; in summer and autumn immersed in the pinnules, in two rows; in winter contained in branched receptacles arising from the denuded branches. No Alga perhaps varies more than the present species does at different seasons of the year. Like several other species, its older stems only may be considered perennial, the more delicate and fruc- tified portions becoming abraded with the storms of autumn and early winter, so that before spring little is left (if the winter has been severe) but the main stem, and a few of the principal branches. At other times, if the winter has been mild, vegetation begins at a very early period, and the month of March finds the plants only partially abraded, or the young fronds again feathering the branches with rich and delicate plumules. From these circumstances, combined with the local influences of tides and currents, this species presents a most puzzling variety of appearances; yet the plant is so much sui generis, that a little acquaintance will soon enable the botanist to determine the species; the chief difficulty being to the young botanist when meeting with the plant in dishabille, while he is drawing his conclusions from figures representing the plant in its most perfect foliage. Still less easy is it to distinguish at all times between this and its congener, II. lycopodioides, the microscopical characters of both being almost the same. In R. lycopodioides, the upper branches are generally longest; in R. subfusca, the opposite is the case. In winter, the former is gene- rally denuded to the simple stem, while in the latter, the principal branches also remain; in the former the branches are generally short and terete, in the latter they are mostly long, loose, and straggling. The former generally grows on the stems of Laminaria digitata, the latter most frequently on rocks. EXPLANATION OF PLATE II. Fig. 1.—Rhodomela subfusca, natural size. 2. —Pinnated (summer) branclilet, with tetraspores in the pinnules. 3. —Tufted sticliidia (winter) with tetraspores. 4. —A tetraspore. 5. —Branchlet with capsule. 6. —A capsule. 7. —Transverse section of the stem. All magnified.
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