240 
PHYSIOLOGY. 
BOOK II. 
quantity of new shoots which it produced, new shoots being 
to it now what young leaves were to it before. 
The third year all that took place the year before is 
repeated : more roots appear ; sap is again absorbed by the 
unfolding leaves ; and its loss is made good by new fluids in- 
troduced by the roots and transmitted through the alburnum 
or wood of the year before ; new wood and liber are deposited 
by matter sent downwards by the buds ; cambium is exuded ; 
the horizontal developement of cellular tissue is repeated, but 
more extensively ; wood towards the end of the year is formed 
more slowly, and has a more compact character ; and another 
ring appears indicative of this year's increase. 
In precisely the same manner as in the second and third 
years of its existence will the plant continue to vegetate, till 
the period of its decay, each successive year being a repetition 
of the phenomena of that which preceded it. 
After a certain number of years the tree arrives at the 
age of puberty : the period at which this occurs is very uncer- 
tain, depending in some measure upon adventitious circum- 
stances, but more upon the idiosyncrasy, or peculiar constitu- 
tion of the individual. About the time when this alteration of 
habit is induced, by the influence of which the sap or blood of 
the plant is to be partially directed from its former courses 
into channels in which its force is to be applied to the pro- 
duction of new individuals rather than to the extension of 
itself ; about this time it will be remarked that certain of 
the young branches do not lengthen, as had been heretofore 
the wont of others, but assume a short stunted appearance, 
probably not growing two inches in the time which had been 
previously sufficient to produce twenty inches of increase. Of 
these little stunted bx'anches, called spurs, the terminal bud 
acquires a swollen appearance, and at length, instead of giving 
birth to new leaves, produces fi'om its bosom a cluster of 
flower-buds, or alabastri, which had been enwrapped 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 pedicel by gentle de- 
grees, is taken up by it, and exposed by the surface of its 
tube and segments to air and light ; but, having very imperfect 
