THE AETIHCIAL SYSTEM OP LINN^US. 511 



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

 provided with slender and active spermatozoids, while the 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- 

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

 Hydropterides ; but its true position is hard to detei-mine. 



CHAPTER IV. 



OF THE ARTIFICIAL SYSTEM OP LINN^US. 



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

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

 one better understood tliis than Linnseus, 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 tliis system is identified with the history 

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

 systematic worlts 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 space 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 relationships being only so far expressed as 

 the plan of the scheme admits. All higher considerations are of 

 course sacrificed to facility. In the Linnaean 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, although those which stand next each other have, it 

 may be, nothing in common beyond the initial letter. 



