542 POPULAR SCIENCE MONTHLY 



Before he attempts to formulate general laws, he must collect his facts, 

 and examine them in detail. He goes out, perhaps, and gathers a 

 flower: let us say the blue flax, Linum lewisii. The very name tells 

 him something of its history; it was called lewisii in honor of Meri- 

 wether Lewis, of the famous Lewis and Clark expedition. It has been 

 known since 1814, and has been collected by many botanists. Turn- 

 ing to the published records, it appears that it has been found as far 

 south as the mountains of Mexico; as far north as Alaska. It does 

 not occur in the eastern part of the continent, north or south. Among 

 the native plants of America it has only one close ally, a smaller plant 

 called Linum pratense — we may call it the prairie flax — which occupies 

 open ground east of the Rocky Mountains from British America to 

 Texas and again appears in Arizona. 



In Europe and Siberia, however, there are closely similar plants; 

 so like our Linum lewisii that for many years our plant was not sepa- 

 rated. Furthermore, there are various other species of Linum or flax 

 in the Old World, some of them strikingly different from ours. These, 

 some with blue, some with red flowers, are more closely related to one 

 another than to the yellow-flowered flaxes, which have lately been placed 

 in a separate genus. 



From all these facts, it is permissible to assume (in the absence of 

 contrary evidence) that the genus Linum, in the restricted sense, 

 belongs especially to and probably originated in the temperate regions 

 of the Old World. This opinion is fortified by the discovery of a 

 species (Linum oligocenicum Conw.) in European amber of Tertiary 

 age. We imagine, then, the true flaxes originating perhaps in central 

 Europe or Asia, segregating into various distinct species, and finally, 

 perhaps during the Miocene period, invading North America. From 

 the present distribution of the plant, we should naturally infer that it 

 came by way of Bering Strait, not across the Atlantic; and from its 

 slight divergence from the Old World stock we should think of it as 

 a comparatively recent immigrant. The prairie flax, occupying a lesser 

 area, and not so similar to the Old World type, is regarded as an 

 offshoot from Lewis's flax, adapted to life on the prairies, the former 

 occupying the mountains. 



Leaving the flax for the moment, our naturalist hunts about and 

 picks up a small shining cylindrical shell known as Cochlicopa lubrica. 

 This snail is distributed widely over the continent, from Canada to 

 Alabama, and west to the Pacific coast region. It is very constant in 

 its characters, but in a few states has given rise to a variety or closely 

 allied form of larger size called morseana. There are no other Amer- 

 ican allies. 



So far, there is no apparent clue to its history ; but when we turn to 

 the eastern hemisphere we find a very different state of affairs. In the 



