

CLASS X. OIIDER IV. 1 OXALIS, 659 



the leaflets of the plant before us is by no means a peculiarity ; but as 



it is a familiar example that may be observed by most persons, we " ^ 



more particularly notice it as an illustration of some of the very in- J^^^^ 



tcresling investigations for the student in the economy of vegetable 



life. In the leaf it is pretty well ascertained that the fluids of the 



plant undergo the most important changes to their further elaboration, 



not only for the perfcclion of the structure of the plant, but for the 



perfect formation of its peculiar secretions; and to the accomplishment 



of this end the action of light is one of the most important agents, 



and, therefore, we see the leaflets during the day are fully exposed 



to its influence ; and by this n)ovement another object is attained, 



namely, the expanded leaflets prevent, by their projection forming a 



covering over the roots, so great an evaporation of moisture as would 



otherwise take place; but during the night, when the heat of the day 



is gone, and the dew begins to be deposited, the leaflets fall, that 



the roots may be fully exposed to the influence of its deposition, to 



the invigoration of the plant, and supplying it with that moisture 



which is evaporated from the leaves during the day. Thus far it may 



be observed are some of the results consequent on the movement of the 



leaflets ; but what the causes of this movement in the leaflets are we 



must leave for the further investigation of the student : to slate the 



imperfect knowledge which we possess of these causes would occupy 



more space than we can here be allowed. 



Another result in consequence of these changes is readily ascer- 

 tained: on tasting the leaves, it will be found that the juices are 

 become of a pleasant acid flavour, which is from chemical investiga- t 



lions ascertained to be oxalic acid, in a state, according to Thomson, of jio 



binoxalate of potash, and it is from the circumstance of this acid being ^ 



found in the leaves that it bears the name. Twenty pounds of the ^ 



leaves yield about six pounds of juice, which properly evaporated, Sec, 

 gives two ounces and half of impure crystalizable salt, which, when ?^ 



purified, forms flat semi-transparent crystals, having an intensely sour 

 taste and active poisonous properties, which, when taken internally in 

 the dose of half an ounce, prove rapidly fatal ; and even in the dose of ^ 



half a drachm they have been known to produce death after a few I - 



days. Oxalic acid of the shops is not now prepared from the juice of t 



vegetables, since Scheele has discovered a method of procuring it by 

 acting upon sugar with nitric acid, and producing the salt by this % 



means more readily, and far more economically. Oxalic acid, when .^ 



mixed with cream of tartar, was sold under the name of salts of lemon, "t\ 



and is useful in removing iron moulds, ink spots, and stains from linen, ' 



as well as various other domestic purposes ; but since the real salts of N 



lemon, citric acid, is become so much cheaper, and at the same time j^' 



better, it has supplied its place. ^ 



The leaves of the Wood-sorrel, notwithstanding the poisonous pro- >^ 



perties which they contain, are used in different parts of the Continent c 



as an ingredient in the spring salads, and form a delicate and very ^ 



