INTRODUCTORY. 13 



Most of these points to which I am here 

 briefly calling your attention are true only of the 

 higher plants, and especially of land-plants. For 

 we must not forget that plants, like animals, differ 

 immensely from one another in dignity, rank, and 

 relative development. There are higher and 

 lower orders. We shall have to consider, there- 

 fore, their grades and classes — to find out why 

 some are big, some small ; some annual, some 

 perennial ; why some are rooted in dry land, while 

 some float freely about in water; why some have 

 soft stems like spinach and celery, while others 

 have hard trunks like the oak and the chestnut. 

 We shall also have to ask ourselves what were 

 the causes which made them differ at first from 

 one another, and to what agencies they owe the 

 various steps in their upward development. In 

 short, we must not rest content with merely say- 

 ing that the rose is like this and the cabbage like 

 that; we must try to find out what gave to each 

 of them its main distinctive features. We must 

 "consider the lilies, how they grow," and must 

 seek to account for their growth and their pecul- 

 iarities. 



And now let me sum up again these central 

 ideas of our future reading on plants and their 

 history. 



Plants are living things; they eat with their 

 leaves, and drink with their rootlets. They take 

 up carbon from the air, and water from the soil, 

 and build the materials so derived into their own 

 bodies. Plants also marry and are given in mar- 

 riage. They have often two sexes, male and 

 female. Each seed is thus the product of a 

 separate father and mother. Plants are of many 

 kinds, and we must inquire by and by how they 



