CHAPTER XLVIL 



CLASSIFICATION OF THE ANGIOSPERMS. 

 Relation of Species, Genus, Family, Order, etc. 



929. Species. It is not necessary for one to be a botanist in 

 order to recognize, during a stroll in the woods where the tril- 

 lium is flowering, that there are many individual plants very 

 like each other. They may vary in size, and the parts may 

 differ a little in form. When the flowers first open they are 

 usually white, and in age they generally become pinkish. In 

 some individuals they are pinkish when they first open. Even 

 with these variations, which are trifling in comparison with the 

 points of close agreement, we recognize the individuals to be of 

 the same kind, just as we recognize the corn plants, grown from 

 the seed of an ear of corn, as of the same kind. Individuals of 

 the same kind, in this sense, form a species. The white wake- 

 robin, then, is a species. 



But there are other trilliums which differ greatly from this one. 

 The purple trillium (T. erectum) shown in fig. 495 is very different 

 from it. So are a number of others. But the purple trillium 

 is a species. It is made up of individuals variable, yet very like 

 one another, more so than any one of them is like the white 

 wake-robin. 



930. Genus. Yet if we study all parts of the plant, the 

 perennial root-stock, the annual shoot, and the parts of the 

 flower, we find a great resemblance. In this respect we find 

 that there are several species which possess the same general 

 characters. In other words, there is a relationship between 



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