TMESIPTERIS. 



[ 643 ] 



TONGUE. 



airo 

 TO , 



structures, where the cells are attenuated to 

 a point at each end, the cells, " fibres/' being 

 intercalated and applied side to side. 



4. Tela context a. This name is used to 

 indicate the interwoven tissue formed by the 

 ramified, jointed filaments of the mycelium 

 of Fungi and the cottony substance in the 

 interior of the thallus of many Lichens. 



5. Fibro-vascular tissue is composed of 

 vessels, ducts, and prosenchymatous cells or 

 "fibres" associated in various ways, forming 

 fibrous or fibro-vascular bundles, which 

 either remain distinct or cohere to form 

 masses of wood. 



a. Fibrous bundles, occurring in liber, in 

 the outer part of many Monocotyledo- 

 nous stems, and in the stems of Mosses, 

 consist of cords formed of prosenchy- 

 matous cells, which are often of great 

 length. 



b. Fibro-vascular bundles, composed of 

 vessels and ducts together with prosen- 

 chyma,form the "woody fibres" of every 

 part (except the bark) of all plants 

 above the Mosses. 



6. Laticiferous tissue and Reservoirs for 

 Secretion, composed either of intercellular 

 passages lined by a proper coat, or of lines 

 of cells fused at their ends, so as to form 

 continuous branched canals ; they occur in 

 the bark, wood, and pith of the Flowering 

 Plants. 



7. Epidermal tissue. Composed of cel- 

 lular tissue, forming a continuous firm layer 

 over the external surface of the higher plants. 

 It is composed usually of a single layer of 

 cells, and presents very varied appendages, 

 such as HAIRS, GLANDS, &c., and is per- 

 forated by STOMATES. Its outer surface is 

 rendered dense by the deposit of CUTICLE. 

 The epidermis is replaced, on stems, by the 

 CORK or sebaceous layer of BARK. 



For further particulars see the various 

 heads above named. 



BIBL. General Works on Botany. 



TMESIPTERIS. A genus of Psilotese 

 (Lycopodiaceae) (fig. f&2\ remarkable for 



Fig. 752. 



Tmesipteris tannensis. 



the peculiar habit and the bivalved sporanges 

 bursting by a vertical crack. 



BIBL. See LYCOPODIACE^E. 



TODEA, Willdenow. A genus of Osmun- 

 daeous Ferns (fig. 753-5). Exotic. 



Fig. 753. Fig. 754. 



Fig. 755. 



Todea africana. 



Sporanges closed and bursting. 

 Magnified 40 diameters. 



TOLYPOTHRIX, Kiitz. A genus of 

 Oscillatoriaceae (Confervoid Algae), appa- 

 rently not very satisfactorily defined. Has- 

 sall describes six species as British, of which 

 T. distorta (PI. 4. fig. 14) is said to be com- 

 mon, adhering to sticks, stems, &c. in stag- 

 nant water, forming tufts from 1-2 to 1" in 

 height, dark green when fresh, verdigris or 

 blue-green when dry; primary filaments 

 1-1800 to 1-1440" in diameter; joints about 

 as long as broad. 



BIBL. Kutz. Sp. Alg. p. 312, Tab. Phyc. 

 ii. pis. 31-33; Hassall, Brit. Freshw. Alg. 

 p. 240. pis. 68 & 69. 



TONGUE. We have only space here to 

 notice the structure of the beautiful papill&e 

 of the human tongue. 



The filiform or conical papillae (fig. 760) 

 are whitish, very numerous, and occupy the 

 intervals between the fungiform papillae. 

 The papilla of the mucous membrane at 

 their bases (p,p) are conical, and covered 

 either at the. end only, or all over the surface 

 with a number of smaller or secondary pa- 

 pillae ; the whole being coated by an epithe- 

 lial investment (e}, terminating in a tuft of 

 free filiform processes (/). The inner layers 

 of the epithelium agree in structure with 

 that of the mouth, whilst the outer layers, 

 and especially the epithelium of the processes, 

 resemble rather the scales of the epidermis, 

 in their hardness, small size and considerable 

 resistance to the action of alkalies and acids. 

 The papillae themselves consist of areolar 

 tissue, with a large number of undulating 

 nuclear fibres, each containing a small ar- 

 tery (a) and vein (b), with an intermediate 

 plexus of looped capillaries, and numerous 

 nerve-tubes. 



2 T 2 



