CRETAOKOUS FLORA. 5 



Involution of the dicotyledons.] 



degree of organization than another. And also, in the large number of vegetable 

 remains of the lower division of plants, none have been found in the long series of 

 ancient vegetables, whose characters would indicate a tendency to a transition to a 

 a higher order. Some ferns of the Trias and the Lias, even of the Carboniferous, 

 are by their outlines, like dicotyledonous leaves, but their nervation is always far 

 different, and. moreover, as said above, the likeness of a leaf can not by itself indi- 

 cate a relation in the characters of a plant, as in passing for example, from a fern to 

 a dicotyledon the whole plant has to be modified, the structure of the stem, the 

 wood, the flowers, fruits, etc. Evolutionists may trace the derivation of a species 

 of mammals from one to another, but they can not look for such transitional forms 

 between a saurian and a mammal; and it is a difference of this kind which exists 

 between the dicotyledons and the lower series of vegetables predominant from the 

 origin of the land plants to the Wealden. 



But more. If the change had proceeded by slow degrees of modification of one 

 species, the results would be, of course, a great uniformity or an affinity of parentage 

 noticeable in the derived types. That is certainly not the case for the flora of the 

 Dakota group, as it is known at the present time, has its dicotyledonous species 

 referable to the three great divisions of the present dicotyledonous flora; the Apeta- 

 lece, the Gamopetalew and the Dialapetalece. Of the first, it has the Amentacece with 

 species of the genera Myrica, Betula, Alnus; the Cupuliferece with Fagus, Quercus, 

 Salix, Populus, Platanus, Liquidambar; the Morece with Ficus; the Proteacece with 

 Proteoides, Todea, Lomatia; the Lauracece with Laurus, Persea, Sassafras, Cinnamomum, 

 Oreodaphne; the Aristolochiece with Aristolochia. Of the second, it has the species of 

 Diospyros in the Diospyrinece and of Andromeda in the Ericacece. Of the third, it has 

 the Araliacece with a number of species of Aralia, and of Hedera; the Ampelidece with 

 Cissus; the Polycarpece with Magnolia, Lvriodendron, Liriophyllum, Anona and a number 

 of species of Menispermacece ; the Malvacece with Sterculia; the Tiliacece with Greviopsis; 

 the Aceracea? with Acerites, and especially Sapindus; the Frangulacece with Ilex, 

 Palinurus, Rhamnus; the Terebinthinece, with Juglans and Rhus; the Rosiflorece with a 

 Pyrus and a Prunus; then species of the Leguminosece with a number of leaves 

 assigned to genera whose affinity with plants of the present epoch is not distinctly 

 marked. How is it possible to admit or even suppose that plants referable to such a 

 number of genera distributed in divers families ot the three essential subdivisions of 

 the dicotyledons might have originated by gradual modifications of one or more 

 species of the inferior classes of plants, to which, as remarked above, it has been 

 impossible to find any kind of analogy, and this, too, during the time of transition 

 between two consecutive periods, the Urgonian and the Cenomanian? 



