TISSUES. 



[ 769 ] 



TONGUE. 



indicate the interwoven tissue formed by 

 the ramified jointed filaments of the my- 

 celium of Fungi, and the cottony substance 

 in the interior of the thallus of many 

 Lichens. 



Fibro- vascular tissue is composed of vessels, 

 ducts, and prosenchymatous cells or "fibres" 

 associated in various ways, forming fibrous 

 or fibre-vascular bundles, which either re- 

 main 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 burdles, composed of 

 vessels and ducts together with pros- 

 enchyma, form the woody fibres of 

 every part (except the bark) of all 

 plants above the Mosses. 



c. Sieve-tubes or Clathrate tissue, found in 

 the bark of Dicotyledons and in the 

 vascular bundles of Monocotyledons. 



Laticiferous tissue and Reservoirs for Se- 

 cretion, 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. 



Epidermal tissue. Composed of cellular 

 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 STOMATA. Its outer surface is 

 rendered dense by the deposit of CUTICLE. 

 The epidermis is replaced, on stems, by the 

 CORK or suberous layer of BARK. 



BIBL. Henfrey-Masters, Sot. ; Sachs, 

 Hot. ; V. Tieghem, Sot. 1881; and the Bibl. 

 of the above heads. 



Fig. 747. 



Tmesipteris tannensis. 



TMESIPTERIS. A genus oi Psiloteas 

 (Lycopodiaceae), remarkable for its peculiar 

 haoit and bivalved sporanges bursting by a 

 vertical crack. See LYCOPODIACEJE. 



TOBACCO. The leaves of Tobacco (Ni- 

 cotiana Tabacum and other species) may be 

 distinguished from the leaves of the plants 

 commonly used for adulteration by the pecu- 

 liar structure of the EPIDERMIS with its 

 hairs (PI. 2. fig. 16), and the form of the 

 section of its Fibro-vascular bundles. Paper, 

 which has been sometimes used, is still 

 more readily detected. The epidermis of 

 the dock-leaf (PI. 2. fig. 17), that of rhu- 

 barb (fig. 18), and of colt's-foot (fig. 19), 

 are also characteristic. As in other similar 

 cases, the nature of a foreign ingredient 

 can only be determined by careful compara- 

 tive investigations. 



BIBL. Hassall, Food $c. ; Prescott, To- 

 bacco and its Adulterations, 1858. 



TO'DEA, WiUdenow. A genus of Os- 

 inundaceous Ferns (figs. 748-50). Four spe- 

 cies. Exotic. 



Fig. 748. Fig. 749. 



Fig. 750. 



Todea afrieana. 



Sporanges closed and bursting. 

 Magnified 40 diameters. 



TOLYPOTH'RIX, Kiitz. A genus of 

 Oscillatoriacese (Confer void Algae), appa- 

 rently not very satisfactorily defined. Has- 

 sall describes six species as British, of which 

 T. distorta (PI. 8. 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. Tolypothrix Dittwynii = 

 Desmonema, Eng. Bot. Supp. no. 2958. 



BIBL. Kiitz. % Alg. 312 ; Tab. Phyc. ii. 

 pis. 31-33; Hassall, Alg. 240, pis. 68 & 69 ; 

 Rabenh. Alg. ii. 273. 



TONGUE. We have only space here to 

 notice the beautiful papillae of the tongue. 



The filiform or conical papillae (fig. 755) 

 are whitish, very numerous, and occupy the 

 intervals between the fungiform papillae. 



3D 



