80 Elementary Species 



trial value. Clover exhibits many varieties, 

 which have been cultivated indiscriminately, 

 and often in motley mixtures. The flower- 

 heads may be red or white, large or small, cylin- 

 dric or rounded, the leaves are broader or nar- 

 rower, with or without white spots of a curious 

 pattern. They may be more or less hairy and 

 so forth. Even the seeds exhibit differences in 

 size, shape or color, and of late Martinet has 

 shown, that by the simple means of picking out 

 seeds of the same pattern, pure strains of clover 

 may be obtained, which are of varying cultural 

 value. In this way the best subspecies or va- 

 rieties may be sought out for separate cultiva- 

 tion. Even the white spots on the leaflets have 

 proved to be constant characters corresponding 

 with noticeable differences in yield. 



Flax is another instance. It was already cul- 

 tivated, or at least made use of during the 

 period of the lake-dwellers, but at that time it 

 was a species referred to as Linum angusti- 

 folium, and not the Linum usitatissimum, which 

 is our present day flax. There are now many 

 subspecies, elementary species, and varieties 

 under cultivation. The oldest of them is known 

 as the " springing flax," in opposition to the 

 ordinary " threshing flax." It has capsules 

 which open of themselves, in order to dissemin- 

 ate the seeds, while the ordinary heads of the 



