ON VEGETATION. 567 



far as we know, the same explanations might be applied to some animal 

 motions; and although it is very possihle that there may be a certain 

 limit, where the influence of mind and sensation terminates, and the laws 

 of vegetable life only prevail ; yet the place of the division is not strongly 

 enough marked, to allow it to form a characteristic in an artificial system. 

 It has been asserted that some worms are nourished by absorption only, 

 without the assistance of a stomach ; thus hydatids, which are supposed 

 to be of an animal nature, appear to be simply bags of a fluid without any 

 visible opening ; but a few doubtful cases of this kind can scarcely be 

 sufficient to invalidate the general position, that all bodies decidedly 

 animal have a cavity for the reception of food. There are usually also 

 some chemical distinctions in the component parts of animals and vegeta- 

 bles ; animal substances commonly containing greater proportions of azote 

 or nitrogen, and of phosphoric acid ; but there are some exceptions to this 

 observation ; thus the carica papaya, or papaw, contains nearly the same 

 principles as are usually found in substances of animal origin. In general 

 we may readily distinguish a small portion of an animal from a vegetable 

 substance, by the smell produced in burning it. According to common 

 language, we say, that minerals have growth only, but not always ; that 

 vegetables grow and live also ; and that animals have sensation, as well as 

 life and increase of magnitude. 



Mineralogy is a branch of natural history so nearly allied to chemistry, 

 that it cannot be completely understood without a previous knowledge of 

 that science. It may therefore be more properly considered as belonging 

 to a course of chemical than of physical lectures. 



The vegetable kingdom presents to us a spectacle highly interesting by 

 its variety and by its elegance ; but the economy of vegetation appears to 

 be little diversified, although little understood. With respect to the appa- 

 rent perfection of their functions, and the complication of their structure, 

 we may consider all vegetables as belonging to two principal divisions, in 

 one of which the seed is prepared with the assistance of a flower, having 

 its stamina and its pistils, with petals or a calyx ; while in the other, the 

 preparation of the seed is less regular and conspicuous, and hence such 

 plants are called cryptogamous. In some of these there is a slight resem- 

 blance to the flowers of other vegetables, but on the whole, the class 

 appears to form one of the connecting links between the three kingdoms of 

 nature ; its physiology is probably simple, but it has been little examined. 

 The herbs, palms, shrubs, and trees, which constitute the numerous genera 

 of flowering vegetables, exhibit the greatest diversity in the forms and dis- 

 positions of the organs of fructification, while they have all a general resem- 

 blance in their internal economy. 



Every vegetable may be considered as a congeries of vessels, in which, by 

 some unknown means, the aqueous fluids, imbibed by its roots, are sub- 

 jected to peculiar chemical and vital actions, and exposed in the leaves to 

 the influence of the light and air ; so as to be rendered fit for becoming 

 constituent parts of the plant, or of the peculiar substances contained 

 within it. 



The first process in the germination of a seed is its imbibing moisture, 



