INTRODUCTORY VIEW 3 



student of field crops to go exhaustively into the subject 

 of systematic botany, a knowledge of its principles is 

 necessary to a satisfactory understanding of field crops 

 and of the terms employed in any discussion of them. 



2. Species. The grouping can best be understood 

 perhaps if we start with the individual. 1 If a seed of 

 Kentucky blue-grass is planted, it will with favorable 

 conditions for growth develop into a plant, which in time 

 will produce seeds for its own perpetuation. If these 

 seeds in turn are planted, they will give rise to other plants, 

 which in time will produce seeds, and so on. Within a 

 few years a large number of plants will result, the progeny 

 of a single blue-grass seed. A careful examination of these 

 plants will show that, while they are very much alike, slight 

 variations occur in size, form and color of their various 

 parts. While these variations may occur, the plants 

 on the whole resemble each other very closely, having 

 descended from a common ancestor. These plants and 

 all others, wherever they may be found, resembling them 

 so closely that they might well have come from the individ- 

 ual plant of which we spoke, are placed in a group called 

 a species. A species, therefore, is made up of individuals 

 so near alike that they may be regarded as having come 

 from a common ancestor. 



3. Variety. As has been noted, slight variations occur 

 among the individual members of a species. Sometimes 

 variation in form, size or structure of a plant or its parts 

 is such as to make it more useful to man than the other 

 members of the species. Frequently man selects plants 

 possessing some superior quality and develops from them, 

 by using their seeds for perpetuation, a group of plants 



1 Method of presenting classification of plants adapted from Percival's 

 Agricultural Botany. 



