Dr. Griffith on the Pitted Tissue of Plants. 95 truncatus. Linn. Gmel. 3008. no. 64 ; Manuel, Enc. Meth. vii. 733. t. 268. f. 30 — 34; Fabricius, Ent. Syst. 498. — Lynceus truncatus, Latreille, Hist. ge'n. des Crust. 206 ; Baird, Trans. Berw. Nat. Club, p. 100 ; M. Edwards, Hist, des Crust, iii. 388. Shell nearly of an oval form ; the lower extremity having a curved projection backwards, and provided with a number of pretty strong spines, about seventeen in number, the three last of which are curved backwards. On the upper extremity of anterior margin there are about an equal number of spines, the upper ones being curved upwards. These are partly con-cealed by the cilia which densely cover the anterior margin of the shell. The shell is striated longitudinally. Beak rounded and sharp-pointed, rather long. Rami short ; anterior branch furnished with five setae, one from first, one from second, and three from last articulation. Posterior branch has three setae, all from last joint. First pair of feet large. Tail rather gib-bous on lower edge, and on latter half has about eight spines, and terminates in two stout claws. Intestine convoluted, having one turn and nearly a half. Antennae conical-shaped. Eye areolar. Accompanying black spot squarish-shaped. Two ova. Hab. Pond at Osterly Park ; ditch near Richmond oppo-site Isleworth church ; near Southall ; " pond on Beaumont water at Yetholm." — Trans. Berw. Nat. Club. XVI. — Observations on the Formation of the Pitted Tissue of Plants, with one or two remarks on the Analogy between the Blood-discs in Animals and the Starch Particles in Ve-getables. By John Wm. Griffith, M.D., F.L.S. &c. [With a Plate.] The object of the present remarks is to point out the mode of formation of the dotted tissue of plants, the cause of the peculiar arrangement of the dots, &c. I shall also allude to one or two points of vegetable anatomy in which my observations differ from those of authors generally. It is well known that the dotted or pitted tissue varies very much in its characters ; sometimes the dots are surrounded by a rim, in other varieties the pits or dots are without it. My observations will apply at present to the latter variety only* ; the cause of the rim surrounding the dot in the former variety is, I think, quite unexplained. The explanation advanced by Dr. Willshiret, * The dot, or elliptical thinner portion of the marking of the doited duct (i. e. the part generally within the rim), I think is formed in the same man-ner as the dots on the spiroid tissue, but I know of no explanation of the origin of the rim. t Annals of Natural History, Aug. 1842.
XVI.—Observations on the Formation of the Pitted Tissue of Plants, with one or two remarks on the Analogy between the Blood-discs in Animals and the Starch Particles in Vegetables
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