WOOL. 



[ 823 ] 



XYLARIA. 



WOOL OF ANIMALS. See HAIR. The 

 fibres of wool are coloured by the test- 

 liquids of Millon and Schultze. 



WRAXGE'LIA, Ag. A genus of Cera- 

 miaceje (Florideous Algrc), differing- from 

 Grijjtthma chiefly in the scattered tetra- 

 spores. W. muJtifda, the only British spe- 

 cies, has rose-red feathery fronds, an inch 

 high, consisting of a main filament, about 

 as thick as a bristle, composed of a single 

 row of cells, bearing long, pinnately-ar- 

 rangfd, patent branches, mostly branching 

 in the same way again. At the articula- 

 tions occur two opposite (or more rarely a 

 whorl of) pinnato-multifid or subdichoto- 

 mous ramelli 1-12 to 1-6" long. The fruc- 

 tification consists of: 1, favellee, borne on 

 stalks at the joints, and surrounded by a 

 whorl of ramelli; and 2, elliptical tetra- 

 spores, opposite, secund or tufted, on 

 the lower part of the ramelli. In some 

 foreign species antheridia have been ob- 

 served in similar situations to the tetra- 

 spores. 



BIBL. Harvey, Mar. Alg. 169, pi. 24 D ; 

 Phyc. Brit. pi. 27 ; Derbes and Solier, Ann. 

 Sc. Nat. 3. xiv. 273, pi. 35 ; Thuret, ibid. 4. 

 iii. 38. 



X. 



XANTHID'IA. The bodies found in 

 flint, and thus called, are probably sporangia 

 of Desrnidiaceffi (PI. 25. figs. 22-28). They 

 have been distributed in genera and species, 

 the description of the characters of which 

 would be useless. 



It is a curious circumstance, that these 

 sporangia should be found in flint, which is 

 of marine origin, considering that the Des- 

 midiacese are none of them marine. 



XANTHID'IUM, Ehr. A genus of Des- 

 rnidiacese. 



Char. Cells single, constricted in the 

 middle; segments compressed, entire, spi- 

 nous, with a circular, usually tuberculated 

 projection near the centre. Spines more 

 than two to each segment. 



X. armatum (PI. 14. fig. 23; fig. 24, 

 empty cell, showing the projections). Seg- 

 ments broadest at the base; spines short, 

 stout, tri- or multi-fid; length 1-180". 



X. fasciddatum (PI. 14. fig. 25). Seg- 

 ments with from four to six pairs of subulate 

 marginal spines; central projections minute, 

 conical, and not beaded ; common ; length 

 1-400". 



Sixteen species, 



BIBL. Ralfs, Br. Desmid. Ill; Rabenht. 

 Alg. iii. 221 ; Archer, l\it 'chard's Infus 



XANTHIOPYX'IS, Ehr. -A genus of 

 fossil Diatomacege, consolidated with PYXI- 

 DICULA. It consisted of those species the 

 margins of the valves of which are furnished 

 with a dentate membrane, or the surface 

 covered with setae or hair-like processes. 

 Bermuda. 



BIRL. Ehr. Ber. Berl Akad. 1844, 264; 

 Kiitz. Sp. Alg. 23 ; Pritchard, Infus. 826. 



XENOD'OCHUS, Schlecht. A genus of 

 Uredinei (Hypodermous Fungi), consisting 

 of black tufts, found on the leaves of Pote- 

 rium, containing microscopic, short, curved, 

 usually shortly stipitate filaments, attenu- 

 ated at each end, composed of a moniliform 

 row of (five to fifteen) globose cells filled 

 with black granules. 



These bodies occur associated with Uredo 

 miniata, of which X. carbonarius appears to 

 be the perfect form. Xenodochus is only 

 distinguished from PHRAGMIDIUM by the 

 greater number of joints. 



BIBL. Schlechtendahl, Linncea, i. 237, 

 pi. 3. fig. 3; Fries, Sum. Veg. 505; Ber- 

 keley, Ann. N. H. i. 263. 



XENOSPH^E'RIA, Trevis. A genus of 

 Micro-lichens, parasitic on the thallus of 

 Solorina saccata. 



Char. Spores 6-8, oblong, 4-6-locular, 

 brown ; sometimes large, irregular, and 

 rnuriform. 



BIBL. Korber, Syst. 326; Lindsay, Qu. 

 Mic. Jn. 1869, 344. 



XESTOLEBE'RIS, Sars. One of the 

 CyiheridcB y with subtriangular valves, higher 

 behind than in front, smooth, with distant 

 papilla; lower antennas with 4 joints; 

 upper 6-jointed, with simple setae, and 

 short. Two living British species, com- 

 mon. 



BIBL. Brady, Tr. Linn. Soc. xxvi. 437. 



XIPHIAS'TER, Murray. A genus of 

 Ixodea (Acarina). Flat, with a long pro- 

 jecting rostrum and long applied palpi ; 

 abdomen beaded behind. X. rostratum, 

 Old Calabar. (Murray, EC. Entom. 201, 



%.) 



XIPHICHPLUS, Brady. One of the 

 Cytheridce, near Paradoxostoma ; with sub- 

 equal, compressed valves, elongate, pointed, 

 thin, and smooth. Two living British spe- 

 cies, rare. (Brady, Nat. Hist. Tr. North. 

 $ Durh. iii. 369). 



^ X YL A'RIA, Schrank. A genus of Sphse- 

 riacei (Ascoinycetous Fungi), several of 

 which are common on rotten wood, stumps 



