HOW PLANTS EAT. 33 



CHAPTER IV. 



HOW PLANTS EAT. 



WE saw in the last chapter how and why plants 

 came to differ from one another, but not why they 

 came to be divided into well-marked groups or 

 kinds, such as primroses, daisies, cabbages, oaks, 

 and willows. In the world around us we observe 

 a great many different sorts of plants, not all 

 mixed up together, so to speak, nor merging into 

 one another by endless gradations, but often 

 clearly marked off by definite lines into groups or 

 families. Thus a primrose is quite distinct from 

 a crocus, and an oak from a maple. For the pres- 

 ent, however, I do not propose to go into the 

 question of how they came to be divided into such 

 natural groups. I will begin by telling you briefly 

 how plants eat and drink, marry and rear families, 

 and then will return later on to this problem of 

 the Origin of Species, as it is called, and the 

 pedigrees and relationships of the leading plant 

 families. 



First of all, then, we will inquire, How Plants 

 Eat. And in this inquiry I will neglect for the 

 most part the very early and simple plants we 

 have already spoken about, and will chiefly deal 

 with those more advanced and complicated types, 

 the flowering plants, with which everybody is fa- 

 miliar. 



Plants Eat with their Leaves. The leaves are, 

 in fact, their mouths and stomachs. 



Now, what is a leaf ? It is usually a rather 

 thin, flat body, often with two parts, a stalk and 



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