EBPEODUCTIVE ORGANS OF PLANTS. 299 



of orders, and Series are groups of classes. In botanical 

 classification as now universally employed — classification 

 after the Natural System — all plants arc separated into 

 two series, as follows : 



1. Flowering Plants {Pho nogums) which produce 

 flowers and seeds with embryos, and 



3. Flowerless Plants [Cryptogams) that have no proper 

 flowers, and are reproduced by spores which are in most 

 cases single cells. This series includes Ferns, Horse-tails, 

 Mosses, Liverworts, Lichens, Sea-weeds, JMushrooms, and 

 Molds. 



The use of classification is to give precision to our no- 

 tions and distinctions, and to facilitate the using and ac- 

 quisition of knowledge. Series, classes, orders, genera, 

 species, and varieties, are as valuable to the naturalist as 

 jngeon holes are to the accountant, or shelves and draw- 

 ers to the merchant. 



Botanical Nomenclature. — So, too, the Latin or Greek 

 names which botanists employ are essential for the discrim- 

 ination of plants, being equally received in all countries, 

 and belonging to all languages where science has a home. 

 They are made necessary not only by the confusion of 

 tongues, but by confusions in each vernacular. 



Botanical usage requires for each plant two names, one 

 to specify the genus, another to indicate the species. 

 Thus all oaks are designated by the Latin word Quercus, 

 while the red oak is Quercus rubra, the A\'hitc oak is 

 Quercus alba, the live oak is Quercus vircnr,, etc. 



The designation of certain important families of plants 

 is derived from a peculiarity in the form or arrangement 

 of the flower. Thus the pulse family, comprising the 

 bean, pea, and vetch, as ^^ ell as lucern and clover, are 

 called Paj7ilionaceoifS plants, from the resemblance of 

 their flowers to a butterfly, (Latin, pa^Jilio). Again, the 

 mustard family, including the radish, turnip, cabbage, wa- 



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