THE AMERICAN BOTANIST 3 



or ribwort, is a smoothish plant witli broad leaves. Pursh's 

 plantain, on the other hand, has narrow leaves densely covered" 

 with hairs, as are the spikes of flowers also, and it follows that 

 the evaporation is thereby reduced to a minimum, thus en- 

 abling the plant to dwell in dry regions. We must conclude 

 that Pursh's plantain acquired its narrower leaves, covered 

 with hairs, and its villous spikes, little by little, through a long 

 period of years or centuries. For, as the old valley or plain on 

 which the ancestral plantain dwelt became drier and yet drier, 

 year by year, such individual plants as were slightly woolly, 

 or had narrower leaves than usual, were best able to with- 

 stand the droughty conditions, and in consequence they and 

 their descendants survived, while all the smooth and wide- 

 leaved plants that did not hug* the immediate w^ater-margin 

 perished. As time went on the woolier and linear-leaved 

 plantains continued to increase in numbers and spread to high- 

 er and drier levels, losing, at length, almost all outward re- 

 semblance to the older form of the lowlands. Hard by the 

 stream, then, is the progenitor of Pursh's plantain, or at any 

 rate, a plant closely resembling it, on the heights are the de- 

 scendants, and the hills that intei*vene roughly represent the 

 ages that have elapsed and the difficulties that have been over- 

 come. 



The members of the parsley tribe, for the most part, bear 

 a strong family likeness to one another. But who would per- 

 ceive, at first blush, that the Cymopteriis of the plains was a 

 member of this group? These plants — there are two species, 

 both called "Cheyenne turnip" by the Sioux — appear in early 

 spring, and their umbels lie close to the surface of the soil. 

 Through the survival of the fittest the Cymoptcrns has come 

 to adopt this habit of growth, thus avoiding the buffeting 

 winds of earliest spring. Another well-marked group is the 

 Composit?e, or sunflower family, the members of which are 

 best known as strong, able-bodied plants, most abundant from 

 mid-summer well into autumn. But early in the year there 



