EBPKODUCTIVE ORGANS OP PLANTS. 337 



the seed. This is true of our cereal and leguminous 

 plants, which commonly reproduce their kind with strik- 

 ing regularity. Varieties of some plants cannot, with 

 certainty, be reproduced unaltered by the seed, but are 

 continued in the possession of their peculiarities by cut- 

 tings, layers, and grafts. The fact that the seeds of a 

 potato, a grape, an apple, or pear cannot be depended 

 upon to reproduce the yariety, may perhaps be more 

 commonly due to unavoidable contact of pollen from 

 other Tarieties (variety-hybridization) than to inability 

 of the mother plant to perpetuate its peculiarities. 

 That such inability often exists is, however, well estab- 

 lished, and is, in general, most obvious in case of varie- 

 ties that have, to the greatest degree, departed from the 

 original specific type and of course, in sterile hybrids. 



The sports which originate in the processes of propa- 

 gating from buds (grafts, tubers, cuttings) are perpet- 

 uated by the same processes. 



Species and Varieties, as established in our botanical 

 literature, are exemplified by the Vine, whose species are 

 vinifera, riparia, labrusca, etc., and some of whose 

 North American Varieties, the results of hybridization, 

 have already been enumerated. 



Genus (plural Genera). — Species which resemble 

 each other in most important points of structure are 

 grouped together by botanists into a genus. Thus the 

 various species of oaks, — white, red, black, scrub, live, 

 etc., — ^taken together, form the Oak-genus Quercus, 

 which has a series of characters common to all oaks 

 (generic characters), that distinguishes them from every 

 other kind of tree or plant. 



Families, or Orders, in botanical language, are 

 groups of genera that agree in certain particulars. Thus 

 the several plants well-known as mallows, hollyhock, 

 okra, and cotton, are representatives of as many different 

 genera. They all agree in a number of points, especially 



