ARTHRODESMUS. 



[ 65 ] 



ASCOMYCETES. 



water ; bearing a ciu'ioiis pod-like nucleated 

 fruit. 



BiBL. Harvey, Brit. Marine Jlgce, 2d ed. 

 p. 24. pi. 5 C. ; Phyc. Brit. t. Ixiv. ; Eng. 

 Bot. t. 546 ; Derbes and Sober, ^nn. des Sc. 

 nat. 3 ser. xiv. p. 33. figs. 18-20. 



ARTHRODESMUS, Ehr.— A genus of 

 Desmidiaceae. 



Char. Cells single, compressed, constricted 

 in tbe middle ; segments entire, witb a single 

 spine on each side. Species : 



1. A.convergens. Segments elliptic (PI. 10. 

 fig. 21)', length 1-598 to 1-539". 



2. A. incus, Kiitz. Segments with trun- 

 cated ends; length 1-1103". 



3. A. minutiis, Kiitz. 



4. A. truncatus, Ehr. 



5. A. suhulatus. 



BiBL. Ralfs, Brit. Desmid. pp. 117, 200; 

 Kiitzing, Sp. Alg. p. 176; Ehrenberg, Infu- 

 sionsth. p. 158. 



ARTHROMITUS, Leidy.— Described as 

 a genus of the Leptothriceae of Kiitzing 

 (Algse Confervoideae). Two species, A. cris- 

 tatus and A. nitidus, were found in the in- 

 testinal canal of lulus marginatus, a kind of 

 millipede. These objects appear to have been 

 imperfect forms of some filamentous Fun- 

 gus. See Parasitic Fungi. 



BiBL. Leidy, On the presence of Entophyta 

 in healthy hiving Animals, Proc. Acad, of 

 Philadelphia, iv. p. 225. 1849, extracted 

 in Ann. Nat. Hist. 2nd ser. v. p. 71. 



ARTHRONEMA, Hassall.— A genus of 

 Oscillatoriese (Confervoid Algae) growing in 

 fresh water, consisting of widely spreading 

 olive-coloured or bro^^n tufts of floating fila- 

 ments, with close and conspicuous cross striae ; 

 the coloured tubes lie singly, in lengths of 

 1-2 to 1'', in a gelatinous sheath, the ends of 

 contiguous lengths overlapping obliquely. 



A. cirrhosum, Hass. Brit. Freshw. Algce, p. 

 238. pi. 78. fig. 7 : Scytonema cirrhosum, 

 Carmich. Hook, Br. Fl. (PI. 4. fig. 20). 



ARTHROSTPHON, Kiitzing. See Pe- 



TALONEMA. 



ARTOTROGUS, Mont.— A genus of Se- 

 pedoniei (Hyphomycetous Fungi) containing 

 one species growing and fructifying in the 

 intercellular passages of germinating pota- 

 toes. 



A. hydnosporus, Mont. Berkeley, Journal 

 of the Horticultural Society, vol. i. p. 3. pi. 4. 

 figs. 27-29. 



ARUM, L. — A genus of Araceae (Flow. 

 Plants). Arum maculatum, the common 

 Cuckoo-pint, has a tuberous rhizome in 

 which is produced much starch. This starch 



is extracted in the same way as Ai-rowroot 

 starch is from the rhizomes of Marantaceae, 

 &c., and is called Portland ArrovM'oot. 

 (PL 36. fig. 11.) See Starch. 



ASCARIS. — A genus of Entozoa, of the 

 order Coelelmintha and family Nematoidea. 



Char. Body cylindrical, narrowed at each 

 end ; head furnished with three tubercles or 

 valves; mouth terminal, situated between 

 the three tubercles; male with one or two 

 spicula. 



The species are very numerous, occurring 

 in all the classes of the Vertebrata and doubt- 

 fully in Insects. They are most commonly 

 found in the alimentary canal. We shall only 

 notice the two species met with in man. 



1. A. lumbricoides. The common round 

 worm. Inhabits the human small intestine ; 

 sometimes found also in that of the ass, 

 wild-boar, pig and ox. Varies in length 

 from 3 to 15"; is of a whitish colour; the head 

 distinct, with the three valves (PI. 16. fig. 9) 

 finely denticulated on their inner border, and 

 each furnished near the summit with a 

 slightly projecting papilla. Female larger 

 and more common than the male. Spicula 

 two. 



2. A.vermicularis (Oxyuris verm.). The 

 human thread- worm. Found usually in the 

 rectum. White ; head frequently appearing 

 winged, or exhibiting two lateral vesicular 

 expansions (PI. 16. fig. 8 a), produced by eu- 

 dosmosis. Mouth round when contracted, 

 exhibiting the three lobes when expanded. 

 (Esophagus {e) containing a triquetrous 

 canal, and separated by a constriction from 

 the spherical stomach {d). Length, female 

 3 to 4-lOths of an inch ; male shorter, with 

 the tail spirally coiled, much more rarely 

 met with. Anus (g) about 1 -8th from the end 

 of the body; spiculum single, with an appen- 

 dage. Uterus consisting of two lobes (h) 

 (ovaries), oviduct (k) opening externally 

 near the middle of the body. 



BiBL. Dujardin, Hist. d. Helminthes ; 

 Blanchard, Ann. d. Sc. nat., Zool., 3 ser. x. ; 

 Cloquet, A nat. d. Vers. Int. 



ASCLEPIADACE^.— A family of Dico- 

 tyledonous flowering-plants, presenting some 

 remarkable characters in the pollen (see 

 Pollen). The stems of some of these 

 plants contain very tenacious fibres, which 

 have been used for oeconomical purposes (see 

 Fibres, vegetable). 



ASCOMYCETES.— An order of Fungi 

 characterized by producing the spores in 

 tubular sacs {asci or thecce), frequently inter- 

 mixed with empty filiform sacs (paraphyses) 



F 



