THE ARTIFICIAL SYSTEM OK LINNiEUS. 511 



the smaller (and lower) contains antheridia of curious structure, 

 provided Avith slender and active spermatozoids, while tlie upper 

 and larger is a sporocarp, formed of a budding cluster of leaves 

 wrapped around a nucleus, which is a spore or sporangium. The 

 order might perhaps have been introduced between the Equise- 

 tacere (to which the verticillate branches show some analogy) and the 

 Hydropterides ; but its true position is hard to determine. 



CHAPTER IV. 



OF THE ARTIFICIAL SYSTEM OF LINN.^US. 



987. The difference in pi-inciple between an artificial and a natu- 

 ral system of classification has already been indicated (715). No 

 one better understood this than Linnjeus, when, finding it impossible 

 in his day to make a natural classification available for ordinary use, 

 he proposed, as a temporary substitute, the elegant artificial scheme 

 which bears his name. As this system is identified with the history 

 of the science, which in its time it so greatly promoted, and as most 

 systematic works have until recently been arranged upon its plan, it 

 is still necessary for the student to understand it. Its principles are 

 so simple, that a brief sj^ace will amply suffice for its explanation. 



988. It must be kept in mind, that an artificial scheme does not 

 attempt to fulfil all the conditions of natural-history classification. 

 Its principal object is to furnish an easy mode of ascertaining the 

 names of plants ; their 2-elationships being only so far expressed as 

 the pljtn of the scheme admits. All higlier considerations are of 

 course sacrificed to facility. In the Linnjean classification, the 

 species of a genus are always kept together, whether or not they all 

 accord with the class or order under which they are placed. Its 

 lower divisions, therefore, namely, the genera and species, are the 

 same as in a natural system. But the genera are arranged in arti- 

 ficial classes and orders, founded on some single technical character, 

 and have no necessary agreement in any other respect ; just as 

 words are alphabetically arranged in a dictionary, for the sake of 

 convenience, althougli those Avliich stand next each other have, it 

 may be, nothing in common bej'ond the initial letter. 



