SPECIES GENUS. 



27 



4S. Again, the former are distinguished for producing seeds 

 composed of determinate parts, as cotyledons (H25) and embryo, 

 while the latter produce certain minute bodies, called spores, 

 having no such distinction of parts. Thus the Phsenogamia are 

 also called Cotyledonous and the Cryptogamia Acotyledo- 

 Nous plants. 



49. Lastly, we find in the Phsenogamia, a system of com- 

 pound organs, such as root, stem, leaf, and flower, successively 

 developed on a determinate plan (US -26), while in the Cryp- 

 togamia, a gi-adual departure from tliis plan commences, and 

 they become simple expansions of cellular tissue, without sym- 

 metry or proportion. 



a. In the following pages we shall first du-ect our attention exclusively to the 

 compound organs of Flowering Plants ; and since, in our descriptions of these 

 organs, frequent references ^vill be made to particular species and genera, for 

 illustrations and examples, it seems proper to subjoin, in tliis place, a brief notice 

 of these fundamental divisions also. 



50. A Species embraces all such individuals as may have 

 originated from a common stock. Such individuals bear an es- 

 sential resemblance to each other, as well as to their common 

 parent, in all their parts. 



a. Thus the white clover, ( Trifolium repens) is a species, embracing thousands 

 of contemporary individuals, scattered over our hills and plains, all of a common 

 descent, and producing other individuals of their own kind from their seed. The 

 innumerable multitudes of individual plants which clothe the earth, are, so far 

 as known, comprehended in about 80,000 species. 



51. To this law of resemblance in plants of a common 

 origin, there are some apparent exceptions. Lidividuals from 

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

 difiering in flavor, or leaves differing in form. Such differences 

 are called varieties. They are never permanent, but exhibit 

 a constant tendency to revert to their original type. 



a. Varieties occur chiefly in cultivated species, ns the apple, potatoe, tulip, 

 Grcranium, &c., occasioned l)y the different circumstances of soil, climate, and 

 cnltare, to which «J«cy a«<» subjected. But they continue distinct only until left to 

 multiply spontaneously n-om seed, in their own proper soil. 



52 A Genus is an assemblage of species, with more points 

 of agreement than of difference, and more closely resembling 

 each other than they resemble any species of other groups. 

 3* 



