VEGETABLE PHYSIOLOGY. 89 



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 the bean and pea the seed vessel opens and lets the seeds 

 fall out ; while in the apple, pear and cherry, the fruit falls 

 entire, inclosing 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 Cratcegus 

 or hawthorn which may be seen in the hedges in the midst of 

 winter, and of Mespilus, or medlar, and a variety of others 

 which continue till the succeeding spring. But these, though 

 tenacious of their hold, detach themselves at last, as well as all 

 others, and bury themselves in the soil, about to give birth to a 

 new individual 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. 



Decay of the Permanent Organs. 



Such then is the process and presumptive rationale of the 

 decay and detachment of the temporary organs of the plant. 

 But there is also a period beyond which even the permanent 

 organs themselves can no longer carry on the process of 

 vegetation. Plants are affected by the infirmities of old age as 

 well as animals, and are found to exhibit also 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 effected 

 with difficulty, as well as assimilation of the proper juice, the 

 descent of which is almost totally obstructed ; the bark becomes 

 thick and woody, and covered with moss and lichens ; the shoots 

 become stinted and diminutive ; and the fruits palpably degen- 

 erate, both in quantity and quality. The smaller or terminal 

 branches fade and decay the first, and then the larger branches 

 also, together with the trunk and root ; the vital principle 

 gradually declines without any chance of recovery, and is at last 



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