DEMxiTIUM. 



[ 192 ] 



DEMODEX. 



septate, spirally coiled, then expanding them- 

 selves with elasticity. 



X. Cladotrichum. Filaments erect, sep- 

 tate, branched; branches and branchlets 

 bearing uniseptate spores at their ti];)s. 



XL Dematium, Filaments erect, septate, 

 with verticillate branchlets below, simple 

 and whip-like above ; spores crowded on the 

 apices of the ramules. 



XII. Cladosporium. Filaments erect, sep- 

 tate above, bearing the spores arranged in 

 rows forming short moniliform branchlets. 



XIII. Macrosporium. Filaments suberect, 

 septate, delicate, evanescent, bearing erect, 

 stipitate spores, with many transverse and 

 usually some longitudinal septa. 



XIV. Arthrinium. Filaments tufted, sub- 

 erect, annulate with opaque thickish septa; 

 spores fusiform, septate, large. 



XV. Camptoum. Filaments as in the 

 preceding; spores ovate, curved, small. 



XVI. Glenospora. Mycelium widely ex- 

 panded, the filaments fasciculate within a 

 common membrane, the apices of the fila- 

 ments free, and producing fertile branches 

 below their tips, on which are borne large 

 spores, often m pairs. 



Allied Genera not hitherto found in Britain. 



Mysfrosporium. Pedicels erect, very sim- 

 ple, septate ; spores cellular, terminal. 



Leptotrichum, Pedicels erect, simple, 

 continuous; spore didymous. 



Blastofrichum. Pedicels ascendino* or 

 floating, very much branched, continuous ; 

 spores oblong, transversely septate. 



Stachyohotrys. Pedicels branched, sep- 

 tate; branches crowned at the tips with 

 whorls of mammillary, very short branchlets, 

 forming a capitulum ; spores didymous. 



Helicotrichum. Filaments creeping, 

 branched, septate only at the tips; spores 

 spirallv curled, somewhat septate. 



DEMATIUM, Pers.— A genus of Dema- 



Fig. 167. 



Fig. 165. 



Fig. 166. 



Dematium griseura. Magnified 200 diameters. 



tiei (Hyphomycetous Fungi), growing upon 

 dry leaves, bark, &c., distinguished by the 

 sporiferous branchlets arising closely toge- 

 ther near the base of the erect filaments. 

 British species : 



1. D. griseum, Pers. (figs. 165-7). On 

 rotten hazel-stumps. Chcetopsis Waughii, 

 Grev. Sc. Crypt. Ft. pi. 236. See Sporo- 



DUM and ECHINOBOTRYUM. 



BiBL. Berk. Hook. Br. Fl. v. pt. 2. p. 338; 

 Ann. Nat. Hist. i. 260. vi. 435 ; Grev. /. c. ; 

 Fries, Summa Veg. 499 ; Corda, Icon, Fung, 

 i. pi. 4. figs. 242, 243. 



DEMODEX, Owen (Smowia, Gerv.).— A 

 genus of Arachnida, the exact systematic 

 position of which is doubtful, although usu- 

 ally placed in the family Acarina. 



Char. Feet terminated by four or five 

 claws, no acetabula ; abdomen annulose. 



D. folliculorum (PI. 2. fig. 42), the Jca- 

 rus , Simonia , or Entozoon follicu- 

 lorum of some authors, inhabits the seba- 

 ceous and hair-follicles of the human skin. 

 Its structure has not been satisfactorily de- 

 termined, the minute size of the various 

 parts rendering it extremely difficult to iso- 

 late them. It varies in length from about 

 1-150 to 1-50". 



At the anterior part of the body are two 

 two-jointed organs (PL 2. fig. 43a), the basal 

 joint longest, the distal smallest, and proba- 

 bly terminated like the feet by claws ; these 

 appear to represent palpi. Between these 

 are two narrow, elongated organs (fig. 43 b), 

 the nature of which is doubtful; by some 

 they are regarded as forming a suctorial 

 rostrum, by others as constituting maxilla? 

 or mandibles. Above these is a triangular 

 labrum (fig. 43 c) ; a labium has also been 

 described. 



Above or upon the basal joint of the palpi 

 are two minute tubercles, one on each side 

 • (fig. 43 d). Similar tubercles are seen upon 

 the dorsal surface of the thorax, between the 

 second and third, and the third and fourth 

 pairs of legs. 



On each side of the thorax are four pairs 

 of very short conical legs ; these are aj)pa- 

 rently three -jointed, and marked by irregular 

 fine transverse striae, and terminated by four 

 or five minute hooks. 



The abdomen is longer than the thorax, 

 tapers posteriorly, and exhibits indications 

 of transverse rings, in the form of numerous 

 delicate transverse lines. 



These animals may be obtained by press- 

 ing out the contents of the follicles existing 

 upon the sides and alae of the nose, especially 



