2 THE AMERICAN BOTANIST 



of herbs we are apt to meet with the bastard toad-flax, wild 

 sweet pea ( Lathynis), or, very rarely, the golden corydalis. 

 Then, as we ascend a little higher, there come the prickly 

 pears, Missouri cactus, and yucca, with all that hardy legion 

 whose members can withstand the droughts and freezing 

 winds. Upon the highest hills where limestone rocks lie ex- 

 posed or near the surface v.e find the Black Hills pine {Piniis 

 ponderosa scopulonun), clustered in groves or growing isolat- 

 ed. Whenever I look upon these hardy conifers facing the 

 boreal blasts on the most elevated ridges, I always recall a line 

 in Pope's Homer : — 



"Where cold Dodona lifts her holy trees," 

 notwithstanding that the trees which shadowed the sacred 

 oracle of Zeus were oaks, not pines. 



\Vhoever obsei*ves vegetal forms in a region where the 

 physical features of the surface are greatly varied throughout 

 restrictecl areas can plainly see the results of the laws of or- 

 ganic evolution, and he sees them as such. Near the water- 

 courses, fortuitously introduced by man, \\e meet the common 

 ribwort (Plantago major) thriving in just such a habitat as 

 is to its liking. It is perfectly adapted to its environment : 

 therefore it v.-ill not change in form or habits. Now ascend 

 the near-by bill a liundred feet or two, and though no rain may 

 have fallen at any time through all the month of June, yet you 

 will find there another kind of plantain — Pursh's plantain 

 {Plantago Piirsliii) it is called. It. like the common species, 

 is adapted to surrounding conditions, and hence it, too, need 

 not. and will not change. But this environment is the dry hill- 

 side, so different from the moist, alluvial flat that constitutes 

 the habitat of the ordinary plantain. Bc^th, however, are plan- 

 tains, and therefore are descended, together with many other 

 species, from a common ancestor. This old-time plantain, 

 like our common ribwort, likely dwelt in moist soil, for there 

 can be no reason for supposing that it began life as a xero- 

 phyte, under conditions of aridity. Our door-yard plantain. 



