TOURMALINE. 



[ 



775 ] 



TRACIIELTNA. 



Achorion. Mycelium somewhat ramose, 

 articulated, joints terminatin<r iu round, oval, 

 or irregular spores (conidia ?). 



Speira. Spores connate into concenhic 

 filaments, fovminpr laminse resembling a 

 horseshoe, tinnlly separating. 



Tri»UJ>afossfroinn. Spores more or less 

 curved, multiseptate, chained in beaded 

 rows, finally separating. 



Gi/rocerus. Spores connate into spirally 

 coiled filaments, finally separating. 



Dicfi/osporium. Spores tongue-shaped, re- 

 ticuliirlv cellular (fig. 172, p. 2(10). 



TOURMALINE.— Sections of the crys- 

 tals of this mineral, cut pnrallel to the axis, 

 were formerly used as polarizers or ana- 

 lyzers. They are now usually replaced by 

 Nicol's prisms (Introduction, p. xx). 

 Crystals of the quiuiue-salt (Quinine) form 

 cheap substitutes for either. The crystals of 

 tourmaline belong to the rhombohedric 

 system. They consist principally of silica 

 with alumina, containing also boracic acid, 

 magnesia, iron, &c. ; but their composition 

 is not constant. 



Good tourmalines are transparent, brown- 

 ish or pinkish ; the colourless ones do not 

 polarize. 



BiBL. Pereira, Polarized Liff/tt; Nau- 

 mann, Mineraloqie, .310. 



TOUS-LES-MOIS.— A kind of fecula 

 consisting of the starch of species of Canna, 

 remarkable for the large size, great transpa- 

 rency, and numerous striae of the granules 

 (PI. 46. fig. 25). The mixture of any of the 

 common kinds of starch Avith Tous-Ies-mois 

 is readily detected by microscopic exami- 

 nation. The granules are excellent sub- 

 jects for studying the physical characters of 

 starch, iu particular the appearance with 

 polarized light (PL 39. fig. 40), &c. See 

 Staech. 



TOXONIDEA, Donkin.— A proposed new 

 genus of Diatomaceas, the fi'ustules of which 

 resemble those of Fleurosir/mn, except that 

 the longitudinal line is curved on each side 

 of the median nodule in the same direction, 

 so as to resemble a bow. Two species. 



T. Grerioriana (PI. 51. fig. 24). 



BiBL. Donlrin, Micr. Jn. 1858, vi. 12 ; 

 Rabenht. Ah/, i. 243. 



TRACHE'A. See Lungs. 



TRACHE'vE OF Insects, &c.— The re- 

 spiratorv tubes of Insects and Arachnida. 



Traclieffi (PI. 34. fig. 17 ; PI. 35. fig. 2 h) 

 are cylindrical tubes containing air. They 

 are broadest at their origin from the spira- 



cles, afterwards branching freely, the minute 

 branches being distributed to all parts of the 

 body and anastomosing freely. By reflecti'd 

 light they appear white, with a metallic 

 lustre, or slightly iridescent ; l)y transmitted 

 light the snuiller ones are black, the larger 

 usually of a violet tint. 



The tracheoe consist of two coats, between 

 which lies a spiral fibre (PI. 34. fig. 17) ; in 

 the larger trunks a second external envelope 

 exists. The fibre becomes more slender and 

 indistinct in the smaller tracheal branches, 

 until it finally disappears. The outer mem- 

 brane appears to arise from the confluence 

 of cells ; for iu the tracheae of caterpillars 

 and other larvae of insects, the remaining 

 nuclei are visible (PI. 34. fig. 17). The 

 inner coat forms a pavement epithelium. 

 The spiral fibre arises from the splitting up 

 of a homogeneous membrane deposited in 

 the space bounded by the confluent cells of 

 the outer membrane. 



In many insects the trachefe are furnished 

 with dilatations forming air-sacs, in which 

 the spiral fibre is absent. 



AVhen larvae are fed with indigo or car- 

 mine, or when the dorsal vessel is injected 

 with colouring-matter, the tracheae become 

 coloured, which some authors believe to 

 arise from the nutritive liquid circulating 

 between the membranes of the tracheae ; 

 whilst by others this circulation, or the ex- 

 istence of a space between the tracheal 

 membranes, is denied. 



BiBL. That of Insects ; Newport, Phil. 

 Tr. 1836, 529; Platner, Miiller's Archiv, 

 1844, xxxviii.; Stein, Verr/l. Anat. Insek- 

 ten; Agassiz, Ann. Sc. Nat. 3. xv. ; Bassy, 

 ibid. ; Joly. ibid. xii. ; Blanchard, Compt. 

 Rend. 1851 ; Ann. N. II. 1852, ix. 74; Du- 

 four, Compt. Bend. 1851, Ann. N. H. 1852, 

 ix. 435; Meyer, Siebold S,- Kolliher's Zeitschr. 

 i. 175 ; Moselev, Pi'oc. Roy. Soc. No. 153. 

 vol. xxii. 344, 1874 ; Gerstacker, SieboJd S,- 

 Kollikers Zeitschr. W. 204, 1874; Landois, 

 Zeit. iviss. Zool. xvii. 



TRACHEA OF Plants.— This name 

 was formerly .applied to the unreliable 

 Spiral Vessels of Plants, from their resem- 

 blance to the tracheaj of Insects. 



TRACIIELI'NA.— A family of Holo- 

 trichous Infusoria. 



Char. Body without regular spiral teeth 

 or foot ; parenchyma excessively contrac- 

 tile ; mouth and oesophagus very dilatable. 



BiBL. Clap. & Lachm. Inf. p. 291. 



