DEPARTMENTS OF SCIENCE. 13 



designated in science throughout the world. For example, 

 Strawberry is the popular name, and Fragaria vesca the Latin 

 or scientific name, of the same plant. In elementary treatises, 

 like the present, for the sake of being readily understood, plants 

 are usually called by their popular names. Yet we earnestly 

 recommend the learner to accustom himself early to the use of 

 the more accurate names employed in science. 



26. The Latin name of a plant is always double generic and 

 specific. Thus Fragaria is generic, or the name of the genus of 

 the plant vesca is specific, or the name of the species. 



27. A Species embraces all such individuals as may havo 

 originated from a common stock. Such individuals bear an 

 essential resemblance to each other as well as to their common 

 parent, in all their parts. For example, the White Clover (Tri- 

 folium repens) is a species embracing thousands of contemporary 

 individuals scattered over our hills and plains, all of common 

 descent, and producing other individuals of their own kind from 

 their seed. 



28. To this law of resemblance in plants of one common origin 

 there are some apparent exceptions. Individuals descended from 

 the same parent often bear flowers differing in color, or fruit 

 differing in flavor, or leaves differing in -form, etc. Such plants 

 are called Varieties. They are never permanent, but exhibit a 

 constant tendency to revert to their original type. Varieties 

 occur chiefly in species maintained by cultivation, as the Apple, 

 Potato, Rose, Dahlia. They also occur more or less in native 

 plants (as Hepatica triloba), often rendering the limits of the 

 species extremely doubtful. They are due to the different cir- 

 cumstances of climate, soil, and culture to which they are sub- 

 jected, and continue distinct only until left again to multiply 

 spontaneously from seed in their own proper soil, dr some other 

 cLange of circumstances. 



29. A Genus is an assemblage of species closely related to each 

 other in the structure of their flowers and fruit, and havino- more 



' O 



points of resemblance than of difference throughout. Thus, the 

 genus Clover (Trifolium) includes many species, as the White 

 Clover (T. repens), the Red Clover (T. pratense), the Buffalo 

 Clover (T. reflex um), etc., agreeing in floral structure and gen- 



