INTRODUCTION TO BOTANY. 
33 
second and third years of its existence, will 
the plant continue to vegetate till the period 
of its decay, each successive year being a re- 
petition of the phenomena of that which pre- 
ceded it. 
" V. After a certain number of years the tree 
arrives at the age of puberty ; the period at 
which this occurs is very uncertain, depending 
in some measure upon adventitious circum- 
stances, but more upon the idiosyncrasy or 
peculiar constitution of the individual. About 
the time when this alteration of habit is in- 
duced, by the influence of which the sap or 
blood of the plant is to be partially diverted 
from its former courses into channels in 
which its force is to be applied to the produc- 
tion of new individuals, rather than to the 
extension of itself ; about this time it will be 
remarked, that certain of the youn^ branches 
do not lengthen, as had been hitherto the wont 
of others, but assume a short stunted appear- 
ance, probably not growing two inches in the 
time which had been previously sufficient to 
produce twenty inches of increase. Of these 
little stunted branches, called spurs, the ter- 
minal bud acquires a swollen appearance, and, 
at length, instead of giving birth to a new 
shoot, produces from its bosom a cluster of 
twigs in the form of pedicles, each terminated 
by a bud, the leaves of which are modified for 
the purposes of reproduction, grow firmly to 
each other, assume peculiar forms and colours, 
and form a flower, which had been wrapped 
and protected from injury during the previous 
winter by several layers of imperfect leaves, 
now brought forth as bracts. Sap is impelled 
into the calyx through the pedicle by gentle 
degrees, is taken up by it, and exposed by the 
surface of its tube and segments to air and 
light; but having very imperfect means of 
returning, all that cannot be consumed by the 
calyx is forced onwards into the circulation of 
the petals, stamens, and pistil. The petals 
unfold themselves of a dazzling white, tinged 
with pink, and expose the stamens ; at the 
same time the disc changes into a saccha- 
rine substance, which is supposed to nourish 
the stamens and pistil, and give them energy 
to perform their functions. 
" At a fitting time the stigmatic surface of 
the pistil being ready to receive the pollen, 
the latter is cast upon it from the anthers, 
which have remained near for that particular 
purpose. When the pollen touches the stigma, 
the grains adhere by means of its viscid sur- 
face, emitting a delicate membraneous tube, 
which pierces into the stigmatic tissue, 
lengthens there, and conveys the matter con- 
tained in the pollen towards the ovules, which 
the tube finally enters by means of their 
foramina. 
" This has no sooner occurred than the 
50. 
petals and stamens fade and fall away : their 
ephemeral but important functions being ac- 
complished. The sap, which is afterwards 
impelled through the peduncle, can only be 
disposed of to the calyx and ovary, where it 
lodges : these two swell and form a young 
fruit," which continues to grow as long as any 
new matter of growth is supplied from the 
parent plant. At this time the surface of the 
fruit performs the functions of leaves in ex- 
posing the juice to light and air ; at a subse- 
quent period it ceases to decompose carbonic 
acid, gains oxygen, loses its green colour, 
assumes the rich ruddy glow of maturity ; 
and the peduncle, no longer a passage for 
fluids, dries up and becomes unequal to sup- 
porting the fruit, which at last falls to the 
earth. Here, if not destroyed by animals, it 
lies and decays ; in the succeeding spring its 
seeds are stimulated into life, strike root in 
the mass of decayed matter which surrounds 
them, and spring forth as new plants to 
undergo all the vicissitudes of their parent. 
" Such are the progressive phenomena in the 
vegetation, not only of the apple, but of all 
trees which are natives of northern climates, 
and of a large part of the herbage of the same 
countries, modified of course by peculiarities 
of structure and constitution, as in annual and 
herbaceous plants, and in those the leaves of 
which are opposite and not alternate ; but all 
the more essential circumstances of their 
growth are the same as those of the apple- 
tree. 
" If we reflect upon these phenomena, our 
minds can scarcely fail to be deeply impressed 
with admiration at the perfect simplicity, and, 
at the same time, faultless skill with which all 
the machinery is contrived, upon which vege- 
table life depends. A few forms of tissue, in- 
terwoven horizontally and perpendicularlj-, 
constitute a stem ; the development by the 
first shoot that the seed produces, of buds 
which grow upon the same plan as the first 
shoot itself, and a constant repetition of the 
same formation, cause an increase in the 
length and breadth of the plant ; an expansion 
of the bark into a leaf, within which ramify 
veins proceeding from the seat of nutritive 
matter in the new shoot, with a provision of 
air-passages in its substance, and of pores on 
its surface, enables the crude fluid sent from 
the root to be elaborated and digested until 
it becomes the peculiar secretion of the species ; 
the contraction of a branch and its leaves 
forms a flower ; the disintegration of the in- 
ternal tissue of a petal forms pollen ; the 
folding inwards of a leaf is sufficient to con- 
stitute a pistil ; and, finally, the gorging of 
the pistil with fluid, which it cannot part 
with, causes the production of a fruit." — Vol. 
ii. p. 139. 
