ON THE DERIVATION OF AMERICAN PLANTS. 733 



their nearest or their only living representatives in the Atlantic States, 

 and, when elsewhere, mainly in Eastern Asia. Several of them, or of 

 species like them, have been detected in our Tertiary deposits west of 

 the Mississippi by Newberry and Lesquereux. Herbaceous plants, as 

 it happens, are rarely preserved in a fossil state, else they would prob- 

 ably supply additional testimony to the antiquity of our existing vege- 

 tation, its wide diffusion over the northern and and more frigid zone, 

 and its enforced migrations under changes of climate. Supposing, 

 then, that our existing vegetation, as a whole, is a continuation of that 

 of the Tertiary period, may we conclude that it absolutely originated 

 then ? Evidently not. The preceding Cretaceous period has furnished 

 to Caruthers in Europe a fossil print like that of the Sequoia gigantea 

 of the famous groves, associated with pines of the same character as 

 those that accompany the present tree ; has furnished to Heer, from 

 Greenland, two more Sequoias, one of them identical with a Tertiary 

 species, and one nearly allied to Sequoia languidrupii, which in turn is 

 a probable ancestor of the Californian redwood ; has furnished to Les- 

 quereux, in North America, the remains of another ancient Sequoia, a 

 glyptotrobus ; a liquidamber, which well represents our sweet-gum- 

 tree ; oaks, analogous to living ones, leaves of a plane-tree, which are 

 also in the Tertiary, and are scarcely distinguishable from our own 

 Platanus Occidentalis ; of a magnolia- and tulip-tree ; and " of a sas- 

 safras undistinguishable from our living species." 



I need not continue the enumeration. The facts will justify the 

 conclusion which Lesquereux a very scrupulous investigator has 

 already announced, that " the essential types of our actual flora are 

 marked in the Cretaceous period, and have come to us after passing, 

 without notable changes, through the Tertiary formations of our conti- 

 nent." According to these views, as regards the plants, at least, the 

 adaptation to successive times and changed conditions has been main- 

 tained, not by absolute reversals, but by gradual modifications. I, for 

 one, cannot doubt that the present existing species are the lineal suc- 

 cessors of those that garnished the earth in the old time before them, 

 and that they were as well adapted to their surroundings then as 

 those which flourish and bloom around us are to their conditions now. 

 Order and exquisite adaptation did not wait for man's coming, nor 

 were they ever stereotyped. Organic Nature, by which I mean the 

 system and vitality of living things, their adaptation to each other 

 and to the world, with all its apparent and indeed real stability, should 

 be likened, not to the ocean, which varies only by tidal oscillations from 

 a fixed level to which it is always returning, but rather to a river 

 so vast that we can neither discern its shores nor reach its sources, 

 whose onward flow is no less actual because too slow to be observed 

 by the ephemera which hover near its surface or are borne upon its 

 bosom. Such ideas as these, though still repugnant to some, and not 

 long since to many, have so possessed the minds of the naturalists of 



