TORULACEI. 



[ 647 ] 



TRACHE.E. 



genera require a thorough examination in a 

 fresh state. 



Synopsis of Genera. 



I. ToRULA. Spores in beaded chains, 

 simple, readih' separating, placed on a short 

 continuous or septate pedicel (fig. 761, PI. 

 20. figs. 7 & 23). 



II. BispORA. Resembling the last, but 

 the spores uni-septate (fig. 60, page 80). 



III. Septonema. Resembling the pre- 

 ceding, but having several transverse septa 

 in the spores (fig. 645, page 57-1). 



IV. Alternaria. Resembling the pre- 

 ceding, but with cellular spores connected 

 by a filiform isthmus (fig. 9, page 2Q). 



V. Sporidesmium. Spores in tufts, 

 straight, subclavate or fusiform, shortly 

 stalked or sessile, transversely septate or 

 cellular (fig. 695, page 608). 



VI. Tetraploa. Spores sessile, quadi-i- 

 septate, coherent in bundles of four, each 

 spore cro\yned with a bristle. 



VII. Sporochisma. " Filaments erect, 

 simple, external membrane inarticulate, cell- 

 contents at length separating into spores, 

 articulated in fours, emerging." 



VIII. Coniothecium. Spores without 

 septa, collected in heaps, finally separating 

 more or less into a powder. 



IX. EcHixoBOTRYUM. Sporcs rouuded- 

 apiculate, collected in fascicles, attached on 

 simple erect, aunulated filaments. 



X. Spiloc^a. Spores globose, simple, 

 adhering firmly together and to the matrix, 

 forming spots laid bare by the separation of 

 the epidermis of the subject infected. 



Doubtful and obscure Genera^ 



Sporendonema. Described as com- 

 posed of erect filaments, containing single 

 rows of spores in the interior. S. muscce 

 {Emjmsa, Cohn) really consists of short, 

 tufted, erect, simple filaments, terminating 

 in a bell-shaped cell (spore or sporange ?), 

 thrown ofi" with elasticitv when mature. 



AcHORioN, Mycelium somewhat ramose, 

 articulated, joints terminating in round, oval 

 or irregular spores (conidia?). 



Speira. Spores connate into concentric 

 filaments, forming laminae resembling a 

 horseshoe, finally separating. 



Trimmatostroma. Spores more or less 

 cm'ved, multiseptate, chained in beaded 

 row^s, finally separating. 



Gyrocerus. Spores connate into spi- 

 rally coiled filaments, finally separating. 



Dictyosporium. Spores tongue-shaped, 

 reticularly cellular (fig. 175, page 208). 



TOURMALINE.— Sectionsofthecrystals 

 of this mineral, cut parallel to the axis,' were 

 formerly used as polarizers or analysers. 

 They are now mostly replaced by Nicol's 

 prisms (Intr. p. xviii); crystals of the 

 quinine-salt (Quinine) form cheap substi- 

 tutes for either. The crystals of tom-maline 

 belong to the rhombohedric system. They 

 consist principally of silica with alumina, 

 also containing 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, Lectures on Polarized 

 Light', Naumann, Miner alogie, 319. 



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 strise of the granules 

 (PL 36. fig. 25). The mixture of any of the 

 common kinds of starch with Tous-les-mois 

 is readily detected by the microscoj^ic exami- 

 nation. The granules are excellent subjects 

 for studying the physical characters of starch, 

 in particular the appearance with polarized 

 light (PI. 31. fig. 40), &c. See Starch. 



TRACHEA. See Lungs (p. 402). 



TRACHEiE, OF Insects, &c. The re- 

 spiratory tubes of Insects and Ai-achnida 

 (Arachnida). 



Trachea? (PI. 2?. fig. 17; PI. 28. fig. 2 h) 

 are cylindi-ical 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. By reflected light they appear white, 

 with a metallic lustre, or slightly iridescent ; 

 by transmitted light the smaller ones are 

 black, the larger usually of a violet tint. 



The tracheae consist of two coats, between 

 which lies a spiral fibre (PI. 27. fig. 17) Tin 

 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 in the tracheae of caterpillars 

 and other larvae of insects, the remaining 

 nuclei are visible (PI. 28. fig. 17). The 

 inner coat forms a pavement epithelium. 

 Tlie spiral fibre arises from the splitting up 

 of a homogeneous membrane deposited in 

 the space bovmded b}- the confluent cells of 

 the outer membrane. 



In many insects the trachete are fiu'nished 



