24 CRETACEOUS AND TERTIARY FLORA. 



With the limited acquaintance we have with the ancient Floras of the 

 world it is not possible to account for the sudden appearance of the Dico- 

 tyledons in the Cretaceous time and for their rapid and wide distribution. 

 Saporta, justly considered as the botanist who has acquired by his vast 

 knowledge the most extensive views on the distribution of the vegetation 

 in the ancient epochs, says, on the subject:^ "The organic evolution to 

 which the Dicotyledons owe their existence and their distribution must 

 have been produced under the influence of very different conditions. It 

 is possible that the evolution has been originally slow and obscure; pos- 

 sibly also it has been accomplished in a concealed or as yet undiscovered' 

 locality, in a separate region, and under the influence of peculiar local cir- 

 cumstances. It is probable that the change may have been accomplished 

 by the mediation of insects, multiplying at a given time the results of 

 crossing and producing some combinations favorable to the growth of these 

 plants. It is even conceivable that a short time may have been sufficient 

 to give origin to plants of this class under the action of causes which are 

 still unknown. Whatever hypothesis may be preferred, the fact of the 

 rapid multiplication of the Dicotyledons and of their simultaneous occur- 

 rence in many localities of the Northern Hemisphere from the beginning 

 of the Cretaceous Cenomanian cannot be contested." 



Yes, in this case, as in many others, we may collect facts, but the work 

 of nature in its mode of proceeding for the creation or modification of 

 species remains inscrutable. We may consider the formation of the 

 Dakota Group as produced by a very slow, gradual, prolonged depression 

 of the Western slope of the continent, bringing up from the South or 

 West the invasion of ocean water charged with muddy materials, period- 

 ically heaped farther and farther inland by powerful tides. We may sup- 

 pose, too, the invading flow as bringing with it seeds or fragments of roots 

 of plants derived fruni a country now covered by the sea, and distributing 

 here and there those germs of vegetable organisms. But all this does not 

 account for much in the solution of the problem; it may explain the dis- 

 tribution; but the first appearance, and it seems the simultaneous multipli- 

 cation, of the dicotyledonous plants remains a fact inconceivable to reason. 



' " Le monde des Plantea," etc., p. 19/7. 



