1S6 



HISTORY OF Tl-m VEGETABLE KINGDOM. 



articulation, that comes asunder of its own ac- 

 cord, for tlie skin of tlie animal in question is 

 forced off, in the manner of a slough, merely hy 

 means of the formation of a new skin beneath it, 

 which has already taken the place of the old skin 

 in the living system, and to which it has just 

 been sho^^^l that there exists nothing whatever 

 analogous in the fall of the leaf; so that, after 

 all, the best reason we can give is, perhaps, that 

 the leaves fall in consequence of their being worn 

 out, and no longer necessary to the immediate 

 process of vegetation, which is evidently divisible 

 into annual stages, commencing with the ap- 

 proach of spring, and terminating with the re- 

 turn of winter, which is to the vital principle ap- 

 parently u, period of rest. If it is necessaiy, 

 however, to attempt an explanation of the pro- 

 cess by which the leaf is made ultimately to de- 

 tach itself from the plant, it may be observed, 

 that it consists wholly in the change that is ef- 

 fected in the articulation uniting the foot stalk 

 to the branch, as is evident from the remarks of 

 Mr Fairburn ; for in the case in which the in- 

 jury extends suddenly beyond the leaf, the leaf 

 may wither and decay, but will not fall off, be- 

 cause the articulation has not been duly pre- 

 pared, and because the vital energy can now no 

 longer act upon it fi'om the intervention of the 

 dead or diseased portion of the plant, beyond 

 which it has withdrawn itself. But in the na- 

 tural process of vegetation the necessary change 

 is effected by the leaf on the one hand, in its 

 yielding to the influence of physical or chemical 

 agencies, and withering and shrinking into nar- 

 rower compass when the usual supply of sap is 

 no longer transmitted to it, and by the vital 

 energy on the other, in its controlling and di- 

 viding of chemical agencies, so as to facilitate the 

 final detachment of the foot stalk, and form the 

 scar necessary to its own protection. And this 

 effect is brought about by the conversion of the 

 substance that cements the respective fibres of 

 the leaf, stalk, and branch together, from a, soft 

 and glutinous to a dry and brittle consistence, 

 analogous to the change that takes place in the 

 seams of the valves of ripening capsules or peri- 

 carps, so that the leaf falls at last merely by force 

 of ita own weight, or of the slightest breath of 

 wind, but without the intervention of any pre- 

 vious chink or crack. If it be necessary to il- 

 lustrate the fall of the leaf by any analogous pro- 

 cess in the animal economy, it may be compared 

 to that of the shedding of the antlers of the stag, 

 or of the hair or feathers of animals, which 

 being, like the leaves of plants, distinct and pe- 

 culiar organs, fall off, and are annually renewed, 

 but do not slough. 



The flowers which, like the leaves, are only 

 temporary organs, are for the most part very 

 short lived; for as the object of their production 

 is merely that of effecting the impregnation of 



the germs, that object is no sooner attained tlian 

 they begin again to give indications of decay, 

 and speedily fall from the plant, so that the most 

 beautiful part of the vegetable is also the most 

 transient. The flower of the night-blowing 

 cereus, the most magnificent of all flowers, no 

 sooner expands than it begins to decay, and be- 

 fore the sun has risen upon it its beauty is gone. 

 The flowers of the poppy and tulip, though very 

 gaudy, are very short lived, and the beautiful 

 blossom of our fruit trees soon begins to fade. 

 The scene often continues beautiful indeed, both 

 in the landscape of nature and of art; but that is 

 more owing to the succession of blossoms on the 

 same or on different plants, than to the perman- 

 ency of individual blossoms. And so also of 

 the flowers that adorn the fields or meadows; 

 they spring up in perpetual succession, but are 

 individually of verj' short duration. 



The fruit which begins to appear conspicuous 

 when the flower falls, expands and increases in 

 volume, and assuming a peculiar hue as it ripens, 

 ultimately detaches itself from the parent plant, 

 and drops into the soil. But it does not, in all 

 cases, detach itself in the same manner; thus in 

 tlie bean and pea, the seed vessel opens and lets 

 the seeds fall out; while in the apple, pear, and 

 cheny, the fruit falls entire, enclosing the seed 

 which escapes when the pericarp decays. Most 

 fruits fall soon after ripening, as the cherry and 

 apricot, if not gathered ; but some remain long 

 attached to the parent plant after being fully 

 ripe, as in the case of the fruit of cratcegits and 

 uwnymus, which may be seen in the hedges in 

 the midst of winter; and of mespilus, whicli 

 continues till the succeeding spring. But these, 

 though tenacious of their hold, detach them- 

 selves at last as well as all others, and bury 

 themselves in the soil about to give birth to new 

 individuals in the germination of the seed. The 

 fall of the flower and fruit is accounted for in 

 the same manner as that of the leaf. 



Such then is the process and probable cause 

 of the decay and detachment of the temporarj^ 

 organs of the plant. But there is also a period 

 beyond which even the permanent organs them- 

 selves can no longer carry on the process of 

 vegetation. Plants are affected by the infirmi- 

 ties of old age as well as animals, and are found 

 to exhibit similar symptoms of approaching 

 dissolution. The root refuses to imbibe the 

 nourishment afforded by the soil ; or if it does 

 imbibe a portion, it is but feebly propelled, and 

 partially distributed through the tubes of the 

 alburnum; the elaboration of the sap is now af- 

 . fected with difficulty, as well as the assimilation, 

 of the proper juice, the descent of which is 

 almost totally obstructed : the bark becomes 

 thick and woody, and covered with moss or 

 lichens; the shoot becomes stunted or diminutive; 

 and the fruits palpably degenerate both in quan- 



