66 



B O T A N Y. 



Vegetable the same spadix. M. Hubert also determined, that 

 1'hyMology. t h e e xtcrion surface of the spadices produced the 

 '""""' same remarkable effect, as well as that the contact of 

 the atmosphere is essential to its production. Mr 

 Hunter, who ranks so deservedly high as a physiolo- 

 gist, made many experiments to determine the heat 

 of vegetables, but they do not appear quite satisfacto- 

 ry. Schoepf, too, made several experiments with 

 similar views, but without obtaining any thing deci- 

 sive. The recent observations of M. M. Lamarck 

 and Senebier on the Arum mactdatum, shew satisfac- 

 torily, that much heat is evolved by that plant at the 

 period of fecundation. 



Power of Planta also possess a power of resisting high de- 

 ictisting grees of heat. " Sonnerat," to repeat the words of 

 beat. Willdenow, " discovered in the island of Luconia a 



rivulet, the water of which is so hot, that a thermo- 

 meter immersed in it rose to 17-i Fahrenheit. Swal- 

 lows, when flying seven feet over it, dropped down 

 motionless. Notwithstanding this heat, he observed 

 on its banks two species of Aspalathus, and the I'itex 

 agnus castus, which, with their roots, swept the wa- 

 ter. In the Island of Tanna, Messrs Forsters found 

 the ground near a volcano as hot as 210 Fahrenheit, 

 and at the same time covered with flowers." 



Dr Smith ascribes the pernicious effects of cold, 

 on. opening buds, to " the increased susceptibility of 

 the vital principle, after it has been revived by the 

 warmth of spring." 



1'rncluction The manner in which this heat is produced, is a 

 qf heat. curious subject of speculation, and little has yet been 

 done in tracing the general facts on which alone a 

 theory can be safely founded. It has been shewn, 

 in the instance of the Arum cordifoliitm, that carbo- 

 nic acid is formed, and that the heat-forming power 

 is confined to the exterior surfaces of the spadices. 

 From tliese, and other facts, Mr Ellis deduces the 

 following conclusions : " That the oxygen gas of 

 the air is converted into carbonic acid, by carbon ex- 

 haled by the living plant, whereby the greater part 

 of the specific caloric of that gas is disengaged. It is 

 to this change of composition in the air, and conse- 

 quent extrication of its heat, that the increased tem- 

 perature observed in plants, during their vegetation, 

 is to be ascribed." These conclusions are unques- 

 tionable, when applied to certain stages of vegeta- 

 tion. Some doubt may be entertained, from the con- 

 tradictory results to which we have already alluded, 

 ef the permanent production of heat in vegetables ; 

 but, from the facts previously stated, we are inclined 

 to believe, that not only a certain portion of heat is 

 necessary for the support of vegetable life, but that 

 an uniformity of temperature is maintained by means 

 of natural processes going on in the plant itself. We 

 have here given the particular facts relative to this 

 subject, because the discussion of the changes effect- 

 ed on the air by vegetable^, is more intimately con- 

 nected with the economy of leaves than that of any 

 other part ; it must, however, be steadily kept in 

 mind, that similar actions go on in all parts, and, 

 Consequently, that the same effects, tending to the 

 came end, are also carried on with an energy propor- 

 tioned to the importance of the efficient organ. 



SECT. VI. Fructification. 



Vegetal 

 Physiolf 



THE mode of inflorescence is extremely various in fi owers 

 different plants, and sometimes forms beautiful dis- 

 tinctive characters. The cause of these variations i 

 as unknown as that of the diversities of form among 

 animals. The fructification of plants next comes un- 

 der review. The definitions of the separate parts have 

 been already given, (Art. 59 68 inclusive, Sect. ii. 

 Part I.) Linnaeus has defined the whole in the fol- 

 lowing terms : " Fructilicatio vegetabilium pars tem- 

 poraria, generatione dicata, antiquum terminans, no- 

 vum incipiens." The parts that compose the fruc- 

 tification are the flowers and the fruit ; each of which 

 contains distinct and separate organs, which we shall 

 first describe, and then give a short sketch of the pe- 

 culiar functions of each. The flower consists of the 

 calyx, the corolla, the stamen or stamens, the pistil 

 or pistils ; and each of these contains other parts, 

 that receive appropriate names. 



The calyx or flower-cup is always present in all Calyx, 

 perfect flowers, and is correctly the external cover- 

 ing of the flower, (Plate LXIX. Figs. 20, 22, 27, p LA1E 

 30, 33.) There are various kinds of flower-cups, LXIX. 

 (Art. 61. Sect. ii. Part. I.) each of which, in turn, Figs. 20, 

 exhibits much variety of character. Linnaeus adopt- 27 i s >' 

 ed the opinion, that this organ proceeded from the 

 bark. The celebrated Jussieu has embraced the same 

 opinion ; but, though ingenious, it is devoid of proof. 

 It appears probable, that its chief use is to protect Uses, 

 the flower, where it exists ; and it may also, as Dr 

 Smith supposes, " often contribute to the growth 

 and strength of the stalk, which supports it as the 

 leaves do that portion of branch below them." The 

 calyx, when green, acts on the air in the same man- 

 ner as leaves do. It also absorbs and transpires in a 

 similar manner. 



The corolla lies within the calyx, enveloping the Corolla 

 generative organs of tlie plant, and constituting the 

 chief beauty of the flower. Its colour is various, 

 even in plants of the same species : The delicate b'.ie 

 of the common speedwell, the rich glow of the rose, 

 and blushing tinge of the pink, are familiar to every 

 one. The corolla is compose!! of two parts ; the pe- 

 tal or petals, and the nectary, (Art. 62, 63, 6k 

 Sect. ii. Part. I. ) The former of these exhibits a 

 rich variety of colours, and may be either simple or 

 moxiopetalous, or compound or polypetaious. Each 

 of these varieties again have other parts, which are 

 sufficiently defined in the terminology. The forms 

 of the corolla are so diversified, that some botanists 

 have founded systems of classification on them, ( Sec 

 History (tf BOTANY.) The internal structure of the 

 corolla is said to be similar to that of organs, differ- 

 ing chiefly in the contained colouring matter, which, 

 according to Mr Ellis, is influenced, acd produced 

 by the same agents that affect the leaf. Little is Uses, 

 known of the uses of this beautiful organ. It pro- 

 bably affords protection to the more delicate parts 

 of the flower, and may, as Linnaeus conjectured, 

 serve to waft the flower up and down in the air, to 

 promote the reciprocal agency of the stamens and 

 pistils. Sprengel has shewn, that the corollas 



