TRYBLIONELLA. 



[ 656 ] 



TUBERCLE. 



TRYBLIONELLA, Smith.— A genus of 

 Diatomaceae. 



Char. Frustules free, linear or elliptical 

 in front view ; valves plane, with parallel 

 transverse (tubular ?) striae, and submarginal 

 or obsolete alae. 



In some a median line is present, in others 

 not. The alse are not marginal, as in Suri- 

 rella, but arise from the surface of the valves, 

 as shown by the diagram of a transverse 

 section in PI. 13. fig. 32. 



T. scutellum (PL 13. fig. 30). Valves 

 elliptical, with a median longitudinal line ; 

 alae very short ; striae faint. Marine -, length 

 1-140". 



T. gracilis (PI. 13. fig. 31). Frustules 

 linear, narrowed at the ends ; valves linear, 

 acuminate, striae coarse; alae distinct. Fresh 

 and brackish water ; length 1-200". 



Four other species. 



BiBL. Smith, Brit. Diat. i. 35. 



TUBER, Mich.— A genus of Tuberacei 

 (Ascomycetous Fungi), to which belongs 

 the common truffle (see Tuberacei). 



TUBERACEI.— A family of Ascomyce- 

 tous Fungi, growing underground or upon 

 the surface, of more or less round form, 

 and solid, fleshy texture, excavated with 

 sinuous cavities, lined by asci, containing 

 usually four or eight spores, elegantly reti- 



Fig. 773. 



Fig. 774. 



Fig. 775. 



Choiromyces Leonis. 



Fig. 773. A peridium. Nat. size. 

 Fig. 774. An ascus with spores. Magnified 400 dia- 

 meters. 

 Fig. 775. Vertical section of a peridium. 



culated or spinulose (fig. 774). The internal 

 substance either dries and grows hard, or 

 falls into a flocculent powder with age. 



Tuber cibarium is the common truffle. 

 Sections of the marbled internal substance 

 show this to be composed of interlacing 

 branched filaments, forming fleshy convolu- 

 tions, between which serpentine cavities are 

 alternately excavated ; branches of the fila- 

 ments free at the surface of the lacunae bear 

 spherical sacs (asci), each containing four 

 globular spores of yellow-brown colour, 

 having an elegantly reticulated outer coat. 

 When the spores germinate, they produce a 

 subterraneous cottony mycelium, which after 

 a time presents villous nodules, in the inte- 

 rior of which the peridia are developed ; as 

 these advance, the villous coats gradually 

 vanish, together with the mycelial structure, 

 and the mature peridia appear free, either a 

 little beneath ( Tuber cibarium), or upon the 

 surface (T. album) of the soil (see also Ela- 



PHOMYCES). 



BiBL. Berk. Brit. Flor. ii. pt. 2. p. 227 ; 

 Tulasne, Ann. des Sc. nat. ser. 2. xvi. p. 5, 

 ser. 3. p. 348, Monog. Fungi Hypogm, Paris 

 1851, Ann. Nat. Hist. 2 ser. viii. p. 19; 

 Lespiault, Ann. des Sc. nat. 3 ser. ii. p. 316; 

 Vittadini, Monog. Tuberacearum ; Monog. 

 Lycopod., Mem. Turin Acad. 2nd ser. v. 

 p. 145. 



TUBERCLE or Tubercular matter. 

 — This morbid deposit consists of three parts, 

 the relative proportions of which are variable; 

 viz. 1. an amorphous transparent basis, ren- 

 dered pale by, and finally soluble in acetic 

 acid; 2, minute granules and molecules, 

 some of them consisting of proteine-com- 

 pounds, others of fatty matter ; and 3. of a 

 number of nuclei, or so-called tubercle-cor- 

 puscles (PI. 30. fig. 9 a), about 1-5000 to 

 1-4000" in size, of an oblong-angular form, 

 containing irregular granules, and unaflFected 

 or simply rendered paler by acetic acid (PI. 

 30. fig. 9 b). 



Tubercular matter is deposited in the sub- 

 stance of the tissues or in the cavities of 

 organs (PI. 30. fig. 8). The corpuscles have 

 been supposed to be peculiar to and charac- 

 teristic of tubercle ; but late researches tend 

 to the conclusion that they are the nuclei of 

 normal cells, the development of which has 

 been arrested. 



When softening occurs, the tuberculous 

 matter usually undergoes fatty degeneration; 

 the number of free fatty granules is much 

 increased, and the tubercle becomes yel- 

 lowish. 



