44 THE VEGETABLE WORLD. 
. 
of an uncoloured serum, holding in suspension numerous and very 
small globules, to which it owes its colouration. This liquid is 
called latex. But what strikes the observer as above all remark- 
able, is the circulating movement which is the property of latex. 
The transparency of the vascular walls, and the presence of the 
granules, render this movement very perceptible in some plants. 
The /atex is very abundant in certain vegetables. Place on the 
object-glass of a microscope, and under a thin plate of glass, for 
instance, a young leaf of Chelidonium laciniatum,—better known as 
2 celandine, which is said to be so named from 
its being in flower when the swallows arrive, 
(Fig. 50), still attached to the branch, or a 
sepal of the same plant, of which the latex is 
an orange yellow; or a petal of the Poppy, 
of which the latex is white; or a stipule of 
Ficus elastica (one of the Caoutchouc trees) ; 
we shall see in all these cases the latex 
descending in one branch of the net-work of 
the laticiferous vessels, and ascending im 
another, returning sometimes to its point of 
departure, and, in one word, circulating with 
‘ a rapidity greater in proportion as the tem- 
perature is warmer and vegetation more 
active. Gutta-percha, caoutchouc, and opium 
proceed from the latex of certain plants. 
The elements entering into the composition 
of the trunks of forest trees are, as we S€@; 
rather complex. Having described each m 
Wig: 60.—Lactiferons veseeia in their turn, it will be instructive to bring”the 
whole of them under the eyes of the reader. 
Fig. 51 represents a section, both horizontal and vertical, of @ 
_ trunk of the Maple (Acer campestre). The substances embraced 
by the lines marked No. 1 represent the wood of the first yeat, 
those in No. 2 the wood formed during the second year, and those 
in No. 3 the substances forming the corticle, or bark. In the 
centre of the stem, M represents the pith, the cells of which are 
polyhedric. The trachea, or medullary sheath, coming next to the 
pith and enveloping it on all sides, are represented by the letters 
