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. 



