94 SCIENTIFIC AGRICULTURE. 



belong to the order rosacea, but they belong to different 

 genera, according to some peculiarity in the organs of each. 



A SPECIES "embraces all such individuals as may have 

 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." This is a subdivision of a genus. 

 The white and red clover both belong to the genus trifolium; 

 but they differ in some minor points sufficiently to place them 

 in different species. 



A variety is a subdivision of a species, and is the last 

 distinction made in any system of classification : varieties in the 

 vegetable kingdom occur principally in the cultivated species; 

 they depend only upon slight differences, as, for instance, the 

 same apple tree, rose bush, or potato vine, may produce fruit, 

 tubers and flowers of different colors, but still alike in all essen- 

 tial characteristics. 



We see through the whole vegetable kingdom, a most 

 marked analogy and connection, from the minutest organized 

 microscopic plant, to the largest forest tree: there are also 

 differences so obvious that there can be no doubt of the pro- 

 priety of arranging them into different groups according to 

 their peculiar characters. 



ELEMENTARY ORGANS OF PLANTS. 



The most simple and elementary form of a plant is that of 

 the embryo, which is produced by, and contained in the seed. 

 This consists of two parts, viz : the plumula and radicle. The 

 plumula is the part which is afterwards developed into the 

 ascending part of the plant, the stem, branches and leaves- 

 The radicle is that which becomes the root, and descends into 

 the earth in search of food and moisture. The ascending part 

 of the young plant is at first merely a minute growing point, 

 enveloped in delicate rudimental leaves, which constitute a 

 lud. 



