750 
REVIEWS. 
have been written about it, it must be admitted, that very little has 
been proved. The same may be said of manures; the theory of 
their action, however, is explained. Pruning and training are a 
part of the art of cultivation, dependent upon a great variety of phy¬ 
siological laws; the brief explanation of which, is the object of the 
present work. The various modes of grafting, are also a part of the 
art of Horticulture, and are deduced from laws explained in the 
work. 
It may not be unacceptable to our readers, if we extract a few pa¬ 
ragraphs to shew the explicit manner in which it is written : as pa¬ 
ragraph 3. Plants are organised bodies, consisting of masses of tis¬ 
sue that is permeable by fluids or gaseous matter, 5. Tissue is cal¬ 
led Cellular when it is composed of minute bladders, which either 
approach the figure of a sphere, or are obviously some modification 
of it, supposed to be caused by extension or lateral compression. 
7. Cellular tissue, otherwise called Parenchyma, constitutes the soft 
and brittle parts of plants; such as pith, pulp, the spaces between 
the veins of leaves, the principal part of the petals; and the like. 
12. Vascular tissue is that in which either an elactic tough thread 
is generated spirally within a tube that is closed and conical at each 
end; or rows of cylindrical cellules, placed end to end, finally be¬ 
come continuous tubes by the loss of their ends. 13. The most re¬ 
markable form of vascular tissue is the Spiral vessel, which has the 
power of unrolling with elasticity when stretched. 30. The office of 
the root, is to absorb food in a fluid or gaseous state; and also to fix 
the plant in the soil, or to some firm support. 31. The latter office 
is essential to the certain and regular performance of the former. 
32. It is not by the whole of their surface that roots absorb food; 
but only by their young and newly formed extremities, called Spon- 
gioles. 33. Hence the preservation of the spongioles in an uninju¬ 
red state is essential to the removal of a plant from one place to ano¬ 
ther. 60. The more erect a stem grows, the more vigorous it is ; 
and the more it deviates from this direction to a horizontal or pendu¬ 
lous position, the less it is vigorous. 92. When leaf-buds grow, they 
develope in three directions; the one horizontal, the other upward, 
and the third downward. 93. The horizontal developement is con¬ 
fined to the cellular system of the bark, pith, and medullary rays. 
94. The upward and downward developements are confined to the 
woody fibre and vascular tissue. 95. In this respect they resemble 
seeds; from which they differ physiologically in propagating the in¬ 
dividual, while seeds can only propagate the species. 
