ARECA. 



[ 61 ] 



ARROW-ROOT. 



capillitium ochraceous, capillitium erect ; 

 peridium ovate. 



6. A. ochroleuca, Fr. Spores and capil- 

 litium pale-ochraceous, peridium globose, 

 evanescent ; smaller than the preceding ; 

 1-12" high. 



ARECA, L. — A genus of flowering plants 

 (Fam, Palmaceae). The albumen of the seed 

 of the Areca catechu, the Areca nut as it is 

 called, affords a good instance of horny con- 

 sistence produced by secondary layers upon 

 the cell-walls (PL 38. figs. 21 & 22). See 

 Albumen (of seeds). 



AREGMA, Fries. See Phragmidium. 



AREOLAR TISSUE of animals. See 

 Cellular Tissue. 



ARGAS, Walck. — A genus of Arachnida, 

 of the order Acarina and family Gamasea. 



Char. Rostrum inferior, concealed, as 

 also the palpi, beneath a projection of the 

 anterior part of the body; under part of 

 body granular, not scaly, and consisting of a 

 single piece ; first joint of the palpi longest ; 

 legs approximate at their insertion, feet 

 terminated bv two claws, but no vesicle. 



These animals are frequently parasitic upon 

 pigeons, fovvls, &c. ; some live in gardens. 



A. reflexus {Rhynchoprion Columhce, 

 Herm.). Body marked with tortuous fur- 

 rows and depressions, yellowish or violet after 

 food. On pigeons, especially when young. 



A. persicus. Blood-red colour, back co- 

 vered with scattered elevated white spots. 

 The venomous bug of Persia ; said to cause 

 death in the human subject. 



There are other species. 



BiBL. Walckeu., Apteres, iii. (Gen^ais). 



ARGULUS,Miill.— AgenusofCrustacea,of 

 the order Siphonostoma and family Argulidse. 



Char. Carapace membranous, covering 

 the cephalothorax like a shield ; antennae 

 four, short, concealed beneath the carapace ; 

 anterior two-jointed, terminal joint hooked, 

 posterior four-jointed ; rostrum acuminate ; 

 five pairs of legs, the place of the first (6th) 

 pair being occupied by two suckers ; second 

 pair short, five-jointed, the two basal joints 

 spinous, the last joint with two small hooks ; 

 the last four pairs of legs two-cleft, and fur- 

 nished with ciliated filiform processes. 



A.foUaceus (PI. 15, fig. 1). Parasitic on 

 the stickle-back {Gasterosteus) and other 

 fishes ; carapace greenish. 



BiBL. V. d. Hoeven, Handb. d. Zool. ; 

 Baird, Brit. Entomostraca. 



ARPACTICUS, Bah-d.— A genus of Ento- 

 mostraca, of the order Copepoda and family 

 Cyclopidae. 



Char. Head undistinguishable from thorax; 

 foot-jaws two pairs, forming strong cheliform 

 hands ; antennae in male furnished with a 

 swollen hinge-like joint; antennules (infe- 

 rior antennae) simple ; legs five pairs, the 

 fifth pair rudimentary ; eye single ; ovary 

 single, 2 species : — 



A. chelifer and J. nobilis. Marine, closely 

 resembling Cyclops. 



BiBL. Baird, Brit. Entom. 



ARRENURUS,Duges.— A genusof Arach- 

 nida, of the order Acarina and family 

 Hycbachnea. 



It contains those species in which the 

 posterior part of the body of the male is 

 narrowed and produced into a truncate or 

 cylindrical appendage. The body of the 

 female is truncated posteriorly. The prolon- 

 gation is terminated by two angles and a 

 sinuous intervening margin. At the middle 

 of the latter is situated the penis; above 

 which are two hooks. In both sexes the 

 back is hard, crustaceous, as if shagreened, 

 or spinous. In some species the thicker 

 layer of the skin is furnished with a number 

 of conical apertures (PI. 2. fig. 12). The 

 eyes are two, distant, blackish. The intes- 

 tinal caeca are distinguishable through the 

 skin. The mouth is round and surroimded 

 by a kind of hood (PI, 2. fig. 13 c). 



Arrenurus viridis, Duges' typical species 

 (PI. 2. fig. 13), has the palpi short and clavate 

 (a); the fom-th joint longest and largest, the 

 fifthfalcate and the mandibles unguiculate (b). 



The species are very numerous and of almost 

 all colours, red, green, yellow, grey, purple. 



BiBL. Walcken. Apteres, iii, ; Duges, 

 Ann. d. Sc. nat., 2 ser. i. ; Koch, Ueber- 

 sicht des Arachnidensystems. 



ARROW-ROOT. — A name given to va- 

 rious kinds of starch, derived from the plant 

 Mar ant a arundinacea, and other species. 

 True West India arrow root is from this 

 (PI. 36. fig. 18) and M. Allonga and M. 

 nobilis (N. O. Marantaceae). East India 

 arrow-root is obtained from species of Cur- 

 cuma (N, O. Zingiberaceae) (PI, 36, fig. 19), 

 but Maranta arundinacea is also gro\^Ti 

 there, as its fecula is brought from Sino-a- 

 pore, Tahitan arrow-root (PL 36, fio. 22) 

 is obtained from the plant called Tacca pin- 

 natifida (N, O, Taccaceae), and the substance 

 called Portland arrow-root (PL 36. fig. 11), 

 is extracted fi'om the Arum maculatum 

 (N. O. Araceae), a common hedge- weed in 

 this country. In all these cases the fecula 

 consists of starch- grains, which are produced 

 in great quantity before the season of rest, in 



