25 
such as albuminous matter, woody material, siarcli, sugar, oily and 
fatty materials, colouring ingredients, and the like. The cells so 
constituted are usually too small to be conveniently seen without the 
aid of a compound microscope, but the pith-cells of the English Elder 
may be distinguished with an ordinary magnifying glass ; those of the 
pulp of an orange by the naked eye, and these latter indeed may, by 
a little patience, be separated one from another.” [In the several 
species of our indigenous Citrf/s these cells are very free 
and separate without the least difficulty. — F.JJ.B.] “All 
plants of whatever kind are made up of cells such as those 
just described, and many have no other structure. In the so-called 
higher plants, however, we meet with tubes and vessels of various 
kinds and shapes differently arranged. Some of these tubes con- 
tain woody deposits, as in those which constitute the wood, or the 
hard shell of stone fruits ; others contain a fine thread or threads 
coiled up in a spiral manner. A spiral Dessel is one which contains 
one or more such threads rolled up within it. Such vessels are found 
almost exclusively in flowering plants, and constitute, therefore, one 
of the marks of distinction between them and flowerless plants. By 
breaking across the leaf stalk of a Strawberry, tlie fine spiral threads 
may be drawn out and rendered visible to the naked eye. These 
tubes and vessels are either eloTigated cells, or coiisist of cells placed 
one over another, the intervening partitions being obliterated. All 
begin existence as globular cells, and become modified in course of 
growth. A mass of cells constitutes what is called //s-swe— cellular 
tissue ; a mass of vessels constitute vasctilar (issue. If the cells con- 
tain much woody deposit, we speak of the resulting tissue as woody. 
Most plants, moreover, are invested by a skin or bark of some kind. 
In its simplest and most common condition this consists of one or 
more layers of flattened cells. Such layers constitute the epidermis^ 
or skin, 
“ The plant, in the majority of cases, is rooted in the earth. In 
other instances it floats in or on the surface of water; its leaves are 
exposed to the atmosphere and to the action of light. Unlike an 
animal, a plant has no separate mouth and storaacli ; its skin presents 
an unbroken surface, or at least exhibits, under natural conditions, 
no aperture through which solid material, however fine, can enter. Its 
cells and vessels are closed on all sides, as a rule, and have not, except 
in rare instances, any direct or imTnediate communication one with 
another. In animals there is a continuous alimentary or food-channel 
from the n:iouth to the stomach and intestines. There is also a series 
of continuous branching tubes devoted to the circulation of the blood, 
anothei set of tubes destined for the passage of air into and out of the 
lungs, and so forth. In plants there is no such series of directly con- 
tinuous tubes permeating the whole organism. Erom these facts it 
may readily be inferred that no solid substance can. enter into or be 
digested in them The plant, then, does not live on solid food, but on 
that which is liquid or gaseous. 
“We have now to see whence it obtains its supplies of such 
nutriment. Rooted in the ground, it has, as a whole, no power of 
locomotion. But though this is true of the plant as a whole, it does 
not apply to the parts of which it is composed. The roots, for 
instance, grow and extend themselves, and they grow most freely iu 
