Il6 EVOLUTION OF TO-DAY. 



pear the Dicotyledons, and the modern forest-trees 

 can be traced back to this time. 



It will be seen that this history represents a contin- 

 ual advance : first, Cryptogams, then Gymnosperms, 

 Monocotyledons, and Dicotyledons, in consecutive 

 order. But no such minute histories have been 

 traced here as we have seen in the animal kingdom. 

 The most remarkable feature of paleobotany, and 

 the only one which offers any serious difficulty, is 

 the appearance of dicotyledonous angiosperms in 

 the upper Cretaceous. In Western North America 

 is found a vast bed of rocks known as the Dakota 

 formation, whose age is by some high authorities 

 considered as lower Cretaceous, and by others as up- 

 per Tertiary. Whichever it may be it is a fact that 

 here suddenly appear the highest plants. Previous 

 to this time no Dicotyledons are known to have ex- 

 isted, but here abruptly appear in a perfect condi- 

 tion a flora almost exactly agreeing with the flora of 

 to-day. There were oaks, poplars, magnolias, ma- 

 ples, beeches, elms, firs, hollies, and hosts of other 

 modern plants, agreeing, as far as can be judged 

 from leaves, even to the species, with those now 

 existing. Indeed the forest of this period must 

 have borne an almost exact resemblance to the 

 forests of to-day. The sudden appearance of such 

 a remarkably diversified flora, and the fact that it 

 has since that time remained almost unchanged, are 

 two great difficulties for evolution to meet. The 

 first can only be met by appealing to the imperfec- 

 tion of the record. To the second difficulty it may 

 be suggested, that the group of plants, once de- 



