THE 



[777] 



THE 



THENA'RDIA. (Named after M. TJie- 

 nard, a French chemist. Nat. ord., Dog 

 banes [Apocynacese]. Linn., 5-Pentandria 

 1-Monogynia.) 



Stove evergreen climber. Cuttings of stubby 

 sidc-ahoots in sand, under a bell-glass, and in 

 heat ; sandy, fibry loam and peat, with a little 

 charcoal. Winter temp., 55 to 60; summer, 

 65 to 85. 



T.floribu'nda (bundled-flowered). 10. Blue. 

 Mexico. 1823. 



THEOBRO'MA. Chocolate-tree. (From 

 theos, a god, and broma, food ; poetically, 

 food for the gods. Nat. ord., Byttneriads 

 [Byttneriaceee]. Linn., IS-Polyadelphia 

 1-Decundria.) 



The seed of T. caca'o is the chief ingredient 

 in chocolate and cocoa. Stove evergreen treea. 

 Cuttings of half-ripened shoots in sand, under 

 a bell-glass, in heat; fibry loam and sandy peat. 

 Winter temp., 55 to 65 ; summer, 65 to 88. 

 T. bi'color (two-coloured). 18. Brown. New 

 Grenada. 1820. 



caca'o (common-cacao). 16. Brown. S.Amer. 



1739. 



Caribts'a (Caribean). Yellow. W. Ind. 1821. 



Guiane'nsis (Guiana). 16. Yellow. Guiana. 1803. 



THEOPHRA'STA. (Named after Theo. 

 phrastus, the father of natural history. 

 Nat. ord.,Ardisiads [Myrsinacese], Linn., 

 5-Pentandria 1-Monogynia.) 



Stove white-flowered evergreens. Cuttings of 

 ripe young shoots in sand, under a bell-glass, in 

 heat*; sandy loam and fibry peat. Winter temp., 

 50 to 58 ; summer, 60 to 85. 

 T. Jussien'i ( Jussieu's). 3. St. Domingo. 1818. 



longtfo'tia (long-leaved). 20. Caraccas. 1828- 



THERMOMETER. This instrument is 

 the only unfailing guide for the gardener 

 in regulating the heat to which he allows 

 the roots and foliage of his plants to be 

 subjected. 



Fahrenheit's is used chiefly in Britain, 

 Holland, and North America, the freez- 

 ing point of water on which is at 82 ; 

 and its boiling point, 212. Reaumur's 

 thermometer was that chiefly used in 

 France before the Revolution, and is that 

 now generally used in Spain, and in some 

 other continental states. In its scale 

 the freezing point is ; and the boiling 

 point, 80. On Celsius or the Centi- 

 grade thermometer, now used throughout 

 France, and in the northern kingdoms of 

 Europe, the freezing point is 0; and the 

 boiling point, 100. Hence, to reduce 

 degrees of temperature of the Centigrade 

 thermometer and of that of Reaumur to 

 degrees of Fahrenheit's scale, and con- 

 versely : 



Rule I. Multiply the Centigrade de- 

 grees by 9, and divide the product by 5 ; 



or multiply the degrees of Reaumur by 

 9, and divide by 4 ; then add 32 to the 

 quotient in either case, and the sum is 

 the degrees of temperature of Fahren- 

 heit's scale. 



Rule 2. From the number of degrees 

 on Fahrenheit's scale subtract 32 ; mul- 

 tiply the remainder by 5 for Centigrade 

 degrees, or by 4 for those of Reaumur's 

 scale, and the product, in either case, 

 being divided by 9, will give the tempera- 

 ture required according to Fahrenheit's. 

 To ascertain the internal temperature 

 of a hothouse, the thermometer should 

 be fixed near its centre, against a pillar, 

 and under a cupola, or little roof, shading 

 it from the sun. 



A self-registering thermometer should 

 be in every house, for it shows the highest 

 and lowest degrees of heat whiuh bave 

 occurred in the twenty-four 

 O hours ; and, therefore, serves as 

 a check upon those to whose 

 care they are intrusted. 



Breyazzi's bark-bed thermome- 

 ter is an excellent instrument 

 for ascertaining the bottom- 

 heat of hot beds, bark-pits, &c. 

 It is a thermometer inclosed in 

 a metal tube, perforated to ad- 

 mit the heat, pointed, so as to 

 be easily thrust down, and with 

 a small door in the side, for 

 observing the degree of tempe- 

 rature shown by the scale. 

 THEBMO'PSIS. (From thermos, a lupine, 

 and opsis, like ; lupine-like shrub. Nat. 

 ord., Leguminous Plants [Fabaceoe]. 

 Linn., IQ-Decandria l-Monogynia. Allied 

 to Piptanthus.) 



Hardy herbaceous yellow-flowered perennials. 

 Chiefly by seeds sown in April; light, sandy loam. 

 T. Cnrsonefnsis (Corgon). 1. July. Altaia. 1820. 



fnba'cea( bean-like). 2. June. N.Amer. 1811. 



lanceola'ta (spear-head-teaoed). 1. June. Si- 



beria. 1779- 



THESPE'SIA. (From thespesws, divine ; 

 one of the trees often planted round 

 places of worship in India. Nat. ord., 

 Malhwworts [Malvaceffi]. Linn., IQ-Mo. 

 nadelphia 8-Polyandria.) 



Stove evergreen trees. Cuttings of stubby 

 side-shoots in sand, in May, under a bell-glass, 

 in bottom-heat; fibry, sandy loam, and a little 

 leaf-mould. Winter temp., 48 to 55; summer, 

 65 to 85. 

 T. grandiflo'ra (large-flowered). 30. Scarlet. 



Point Rico. 1837. 



popu'lnea (poplu-leaved). SO. White. E.Ind. 



1770. 



P. Guadalvpc'niil (Gtt(Woupe). SO, Gua- 



daloupe, 



