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A plant in all its parts consists of minute cells or tubes, to which the general 
name of tissue is given. Tissue is divided into two kinds, cellular and vascular. 
Cellular tissue consists of small cavities or vesicles, whose length does not 
greatly exceed their breadth. Vascular tissue consists of similar cavities or 
tubes which are more or less elongated. These variously modified or combined 
constitute the elementary organs of plants, out of which the compound organs 
are formed. Cellular tissue is the only elementary organ universally found in 
plants. The simplest kinds of plants, as mushrooms and sea-weeds, are com¬ 
posed entirely of cellular tissue. The pulpy and succulent parts of the higher 
tribes of plants contain much cellular tissue. The pith of trees and the medul¬ 
lary rays proceeding from the pith to the bark, and commonly known as the 
silver grain are composed of cellular tissue. The green part between the reins 
of leaves (parenchyma) is cellular tissue. It is the tissue first generated when 
the bark or w r ood is wounded; it forms the callus at the base of a cutting be- 
fore roots are emitted. The points or extremities of roots consist of it alone, 
and from the cellular tissue of the medullary system, leaf-buds are generated. 
It is also the tissue in which various secretions, as starch, sugar, oil, &c., are 
deposited. 
Vascular tissue consists of tubes whose length greatly exceeds their breadth. 
Woody fibre or ligneous tissue consists of long cylindrical spindle-shaped tubes, 
which adhere closely together and overlap each other at the ends. This tissue 
is found in the wood, in the veins of leaves, and in the inner bark. Its func¬ 
tions are to give strength to the plant and transmit fluids from the roots to the 
leaves. If we macerate a leaf in water, the comparatively soft cellular paren¬ 
chyma may be easily separated from the tough veins of woody fibre. Flax 
and hemp consist of woody fibre and are obtained in this manner: ‘‘The finest 
thread of flax when magnified 180 times is found to be composed of a great 
number of tubes.-”—(Lindley.) Cotton is considered to be a form of cellular 
tissue. 
Fibro-vascular tissue also consists of cylindrical tubes tapering to each end. 
The sides of the tubes are very much thinner than those of ligneous tissue, and 
they have a spiral fibre or fibres coiled up in their inside, they are found in 
the medullary sheath, in the veins of leaves, and in the petals of flowers. The 
spiral fibres are very elastic, and may be unrolled when stretched. By pulling 
asunder the petal of a rose across the veins, these fibres may be seen by the 
naked eye. Spiral vessels are supposed to convey air; they have been found 
to contain 7 or 8 per cent, more oxygenjlian the atmosphere. 
