304 A NATURALIST IN THE GREAT LAKES REGION 



Finally a great many of our plants and animals are common 

 to Northern Eurasia and Northern North America, while some 

 of ours have their nearest relatives along the eastern edge of 

 Asia. Our common bluebird (Sialia sialis) has an isolated close 

 relative {Sialia codicolor) in Eastern Asia. Our spoonbill and 

 carp sucker, the former a peculiar mud-eating fish, have each 

 a near relative in China. Our crayfishes are more nearly related 

 to those of Eastern Asia than to the species of our own Pacific 

 Coast or of Eastern Europe. Our dragon flies, Hageniiis and 

 Boyeria, have close relatives in Eastern Asia. The tulip tree, 

 sweet gum, and sour gum all belong to genera found nowhere 

 else in the world except Eastern North America and Eastern Asia. 



Confining our attention to the ferns, horsetails, and club 

 mosses, the following are common to Europe and North America, 

 including our Great Lakes region : Poly podium vulgare, Aspidiiwi 

 cristatum, A. spinulosum, Osmuiida regalis, Eqiiisetum fliiviatile, 

 and E. hyemale. In Asia and our region are found Cryptogramma 

 Stellari, Asplenium acrostichoides, Onoclea sensihilis, Osmunda 

 Claytoniana. While common to Eurasia and North America and 

 found in our region are such forms as Phegopteris polypodioides, 

 P. Dryopteris, Onoclea Strutliioptcris, Osmunda cinnamomea, 

 Ophioglossum vulgatiim, Botrychinm ternatum, Equisetum pratense, 

 E. syhaticum, E. variegatum, Lycopodium annotinum, and 

 L. complanatum. 



It must be evident, then, that much of the fauna and flora 

 in the northern part of the world before the glacial advance 

 began was common to Eurasia and North America, and that 

 this life common to the two continents included many forms now 

 found pretty well south. Possibly, too, since the glacier 

 retreated there has been land continuity between Asia and 

 North America, and an invasion route has led from Eastern 

 North America through the Northwest to Asia with movements 

 of plants and animals proceeding in both directions. Much 

 additional evidence must be accumulated before this last point 

 can be satisfactorily settled. 



