INTRODUCTION. XIX 



exercised in nutrition, developement, and reproduction. The principal 

 part of the nourishment of plants, is derived from their roots ; and 

 their texture is composed of tissues and vessels formed for absorbing, 

 retaining, and elaborating the nutritive juices, drawn from the soil 

 and atmosphere. The vegetable kingdom, likewise, has this analogy 

 among others, with the animal ; that the function of reproduction is 

 performed through the medium of sexual organs. These organs are 

 protected by the corolla, or flower ; and all the display of color and 

 form in this essential part of vegetables, is, like the notes of many 

 birds, connected with the important purpose of the continuation of the 

 species. The number, form, and situation of these organs, has afford- 

 ed to Linnaeus the chief characters in his simple, though artificial 

 arrangement of the classes and orders of plants, in consequence termed 

 the sexual system ; while what is called the natural system, proposed 

 by Jussieu, is founded chiefly upon the presence or absence, and the 

 nature of the seed, or germ — the relative position of the stamina — 

 and upon the absence or presence, and form, of the corolla. 



The Mineral Kingdom is distinguished from the other two great 

 divisions, by the absence of vitality and organic structure. Forming 

 the solid crust of the globe, the mineral kingdom, in its various com- 

 pounds, affords support and sustenance to the organized beings existing 

 on its surface. The constitution and arrangement of the mineral 

 strata have given rise to various theories, to account for their present 

 appearance ; but facts have not yet been sufficiently multiplied to 

 afford a satisfactory solution. One great line, however, is drawn be- 

 tween those mineral strata which have been termed primitive, in 

 which no organized remains occur, and those of posterior formation, 

 in which the remains of plants and animals are discovered. The 

 principal external characters of the mineral kingdom are taken from 

 their specific gravity, as compared with water, — hardness, — crystalli- 

 zation, when it exists, — and cleavage, or the direction of the lamellae, 

 which, in many minerals, is regulated by the relation of the external 

 surfaces to the primary crystal, or form. Of a less constant kind are 

 color, degree of transparency, fracture, and the streak Avhich many 

 minerals show, when scratched. The physical characters are fusibi- 

 lity, solubility, phosphorescence, electricity, magnetism, and refraction. 



Linnseus, in his Systema Natures, arranged the Animal kingdom 

 into six classes, the Vegetable kingdom into twenty-four, and the 

 Mineral kingdom into three. As this arrangement, though now 

 .nndified and extended in many of its parts, as will be detailed else* 



