HISTORY OF THE VEGETABLE KINGDOM. 



table actions also have a considerable influence 

 on atmospheric electricity, and on the liumidity 

 and dryness of the air. 



Vegetables so assimilate inorganic matters, 

 as to convert them into the food of animals ; 

 every animal, either directly or indirectly, 

 deriving its chief nourishment from vegetable 

 products. No animal is found capable of sup- 

 porting itself on air, water, or earthy matter 

 alone. Fishes and birds prey upon minute flies 

 and insects, which derive their nourislxment from 

 vegetable matters. Numerous quadrupeds derive 

 their sole support from grasses, and many species 

 of birds from grain and seeds. These become 

 the prey of flesh-feeding animals, and afford 

 them their sole means of subsistence ; and man, 

 as well as some other animals, lives both on vege- 

 table and animal matter. 



The vegetation of former ages, floated down 

 by rivers, and accumulated in the earth's strata, 

 has been converted into coal, to supply the wants 

 of man under a changed climate. Lastly, the 

 decay of vegetation is continually forming fresh 

 soil, by which fresh plants are reared, and newly 

 found countries are rendered habitable. Thus, 

 a seed of a minute lichen clings to a bare and 

 baiTen rock ; others spring from the parent, and 

 accumulate round it ; in process of time they 

 decay, new ones succeed them, and thus a suffi- 

 cient soil is formed for the seeds of larger and 

 more perfect plants. 



CHAP III. 



THE STRUCTURE OP PLANTS. 



Plants are said to he organised bodies, because 

 they have a structure quite different fi-om that 

 of inorganic substances ; a structure made up of 

 cells, fibres, tubes, and membranes, which join 

 together to form distinct parts and organs. Some 

 have endeavoured to trace this structure to certain 

 primitive forms, existing in the rudest beginnings 

 of vegetables, as well as in all parts of perfect 

 plants. When vegetable matter is examined 

 by the aid of a microscope, we discover more or 

 less of these forms. In the lowest organic bodies, 

 both of the animal and vegetable kingdom, we 

 find, by the aid of a powerful magnifier, a spher- 

 ical structure intermixed with spiculi, or thi'eads, 

 in the fluids and solids composing their parts. 

 The simplest plants, as well as the ini'usory 

 animalcules, have this structure. Treviranus 

 saw it in the spa'vvn of frogs, and in the muscu- 

 lar textm-e of the higher animals, in the marrow 

 of frogs, and in the nerves of the garden snail. 

 We find the same combination of round bodies 

 and threads, or spiculi, in the sap of plants ; hence 

 some have supposed, that from these are evolved 



the peculiar primitive forms of the vegetable 

 kingdom. The structural forms found in vege- 

 tables may be reduced to thi-ee : the cellular, the 

 tubular, and the epfral. 



The cellular tissue is com- 

 3- posed of numerous cells con- 



tiguous to each other, of 

 varied form, according to the 

 resistance which they meet 

 with, but generally assuming 

 a six-sided structure, fig. a. 

 Some have compared this cell - 

 ular tissue to the froth or light 

 foam which is produced by 

 blowing up a mixture of 

 soap and water ; others 

 have likened it to the combs of the honey bee, 

 which, indeed, afford a very good illustration of 

 its general appearance. Sometimes it assumes 

 the simple form of a number of spheres slightly 

 adhering together, fig. h. It was at one time 

 generally supposed that the 

 walls of two contiguous cells 

 were common to both, till 

 Malpighi conceived the idea 

 that each cell was a distinct 

 and perfect vesicle of itself, 

 and which he tei-med utricle. 

 This opinion has since been 

 confirmed by Sprengel and numerous other ob- 

 servers. The cells may be separated without tear- 

 ing, which proves that each cell foi-ms a kind of 

 small vesicle which has distinct walls, and that 

 where the two cells meet, the membrane which 

 separates them is formed of two layers, which 

 belong respectively to each of them. 



The investigations of Dutrochet and Amici 

 confirm this opinion. This separation of the 

 vesicles forming tjie cellular tissue, can be ef- 

 fected either by simple boiling in water, or in 

 nitric acid ; but the walls of the cells sometimes 

 so intimately adhere to each other, that it is 

 impossible to separate them. When we observe 

 particularly the growth and successive forma- 

 tion of the cellular tissue, it will be distinctly 

 seen that it is made up of cells at first insulated, 

 but which, in process of their developement, 

 become at last more or less united. In this 

 tissue, the microscope displays to us oval or 

 spherical bodies, generally of a green colour, 

 but yet exhibiting all possible shades, according 

 to the position in which they are observed. It 

 is these small bodies that give colour to the cel- 

 lular tissue, for the sides of the cells themselves 

 are colourless and diaphanous. Turpin has 

 called these bodies glohuline ; within each of 

 them may be seen a small vesicle, in which other 

 small granules are successively formed, which. 

 aiTiving at their full development, burst asunder 

 their enveloping cases. Each of these again be- 

 comes a small vesicle, in which new granules are 



