2 THE WORLD OF LIFE 



land-shells and sea-shells, and ultimately to everything which 

 by moving and feeding, by growing and dying, showed that 

 it was, like himself, alive. Here, probably, he would rest for 

 awhile, and it might require several generations of incipient 

 philosophers to extend the great generalisation of " life " to 

 that omnipresent clothing of the earth's surface produced by 

 the infinitely varied forms of vegetation. The more familiar 

 any phenomenon is — the more it is absolutely essential to 

 our life and well-being — the less attention we pay to it and 

 the less it seems to need any special explanation. Trees, 

 shrubs, and herbs, being outgrowths from the soil, being 

 incapable of any bodily motion and usually exhibiting no 

 indications of sensation, might well have been looked upon 

 as a necessary appendage of the earth, analogous to the hair 

 of mammals or the feathers of birds. It was probably long 

 before their endless diversity attracted much notice, except 

 in so far as the fruits or the roots were eatable, or the stems 

 or foliage or bark useful for huts or clothing ; while the idea 

 that there is in them any essential feature connecting them 

 with animals and entitling them to be classed all together 

 as members of the great world of life would only arise at a 

 considerably later stage of development. 



It is, in fact, only in recent times that the very close 

 resemblance of plants and animals has been generally 

 recognised. The basis of the structure of both is the almost 

 indistinguishable cell ; both grow from germs ; both have a 

 varied life-period from a few months to a maximum of a 

 few hundreds of years ; both in all their more highly organised 

 forms, and in many of their lower types also, are bisexual ; 

 both consist of an immense variety of distinct species, which 

 can be classified in the same way into higher and higher 

 groups ; the laws of variation, heredity, and the struggle for 

 existence apply equally to both, and their evolution under 

 these laws has gone on in a parallel course from the earliest 

 periods of the geological record. 



The differences between plants and animals are, however, 

 equally prominent and fundamental. The former are, with 

 few exceptions, permanently attached to the soil ; they 

 absorb nourishment in the liquid or gaseous state only, and 

 their tissues are almost wholly built up from inorganic 



