COMPARATIVE PHYSIOLOGY. 23 



it is ranked among animals ; and so also with corals. And, although 

 we show hereafter how plants grow, yet it may not appear plain how 

 they live. They live, it is true, like animals, by the food they receive 

 and assimilate, yet the generation of the vital principle which consti- 

 tutes life is not explained. By observing, however, the facts which are 

 hereafter stated, it will be seen how they live best, how they decay, 

 and how they die. 



dge of Plants Many small funguses, called moulds, live but a few 

 hours, or not longer at most than a few days. Garden plants and 

 mosses live but one season, dying of old age as soon as they ripen 

 their seeds. Others live two years, and sometimes three, if their flow- 

 ering is prevented, such as the fox-glove and hollyhock. These are the 

 annual and biennial shrubs, herbs, etc. Many live not only through the 

 winter, but are perpetually, or perennially green. Such are evergreens 

 or forest trees. These live oftentimes for many centuries, producing 

 annually new leaves. Thus the olive, vine, oak, cedar and chesnut, 

 live three hundred, and even a thousand years. The dragon's-blood 

 of Tenerifle is estimated to be two thousand, or more, years old ; and the 

 banian may be six thousand. The interior of trees often becomes too 

 compact for the sap to circulate, or for the formation of new vessels, 

 its moisture passes into younger wood, and the fibres shrink and be- 

 come powder : but the outer parts live, and the tree survives, even for 

 centuries. 



Comparative Physiology of Plants. 



An observance of the relations between animals and plants is highly 

 instructive and entertaining. Many of the most important functions 

 in the life and growth of plants, are seen to be not only analogous, but 

 apparently the same as in animals. This cannot fail to arrest the at- 

 tention of the common observer, as well as of the naturalist. It is 

 frequently alluded to by some writers, who, at the same time, affect to 

 scout the idea of there being any thing more in all this than a seem, 

 ing resemblance." The coincidences are so striking, that constant 

 reference is made to them without a show of reason for dissenting 

 from the conclusion of their functional identity. But the reference is 

 followed by the assumption that the distinctions are, nevertheless, so 

 obvious, that any other conclusions than those they draw would be 

 inadmissible. This assumed guardianship of men's opinions, without 

 facts as a basis for their declarations, cannot have escaped the atten- 

 tion of the general reader. The ostensible reason for this is founded 

 in the narrow conclusion, that to infer a common dispensation of 

 the gifts of Supreme Power and Wisdom in the endowments of or- 



