318 GEOLOGICAL SUEVEY OF THE TERRITORIES. 



e^^dence of the progress of their researches, a catalogue, names only, of 

 seventy species of their Belgian Cretaceous plants. But after they had 

 enlarged their collection of specimens, and pursued their work of compar- 

 ison, they were soon called to review their first determinations and to 

 acknowledge that very few of their former specifications could be pre- 

 served, as they had to unite in one species a number of forms which were 

 first considered as dilferent, or to separate some others which they had 

 formerly admitted as identical. In 1850 the great herbarium of the 

 Botanical Garden of London was opened to them, and they had free ac- 

 cess to the immense materials, especially exotic species of plants of the 

 present time, which they wished to have for comparing the vegetable 

 forms of the Cretaceous. In 1851 the celebrated authors published an- 

 other short general review of the Cretaceous flora of Maestrich. These 

 were merely introductory memoirs to the work which they had under- 

 taken, and for which they acknowledge the assistance received, not only 

 by direct communications of the greatest botanists and paleontologists 

 of the time, Brongniart, Decaisue, Hooker, &c., but also by the free use 

 of the largest botanical and paleontological collections of Europe, and 

 of scientific libraries, where they could study, from its origin, the lit- 

 erature referable to vegetable paleontology; ^lU the papers, even the 

 most unimportant, which have been published on the subject. It was 

 only, in 1859, and after nearly fifteen years of study, that the first 

 and second parts of their work were published. The first, concerning the 

 Thallophytes, describes and represents, in three plates, eighteen species 

 of Fucoids, or marine plants, four species of Fungi, and one Lichen. 

 The second part, on the Acrobriae, describes, with figures, forty-one spe- 

 cies of Ferns, and two species of doubtful relation to this family. 

 Since then nothing more of this work has been published, and we know 

 the dicotyledonous leaves, whose remains are said to abound in the Bel- 

 gian Cretaceous formation, merely by some generalities related to their 

 classification and a few generic names. 



The work of the European authors is certainly of the highest scien- 

 tific order, and might be taken as a model to be followed for proceeding 

 in paleontological researches in our country. But who could work ten 

 tofiiteen years in preparing the publication of a report, when in his re- 

 searches a naturalist does not find any materials for comparison. We 

 have, as yet, no valuable collections in vegetable paleontology, and it is 

 especially because the first materials have to be carefully prepared for 

 institutions of this kind, that the paleontologist is called to review and 

 correct his determinations as fast as new materials are prepared for ex- 

 amination. 



The plants of the Dakota group, as known mostly by detached 

 leaves, are striking by the beauty, the elegance, the variety of their 

 forms, and of their size. In all this they are fully comparable to those 

 of any geological epoch as well as to those of our time. From entirely 

 developed leaves, less than one inch in size, they show all the gradations 

 of size to one foot, even to one foot and one-half in diameter. The 

 multiplicity of forms recognized for a single species is quite as marked 

 as it might be upon any tree of our forests. Aiid to expose the admira- 

 ble elegance of their forms, it sufBces to say that, at first sight, tbey 

 forcibly recall those of the most admired species of our time: the tulip- 

 tree, the magnolia, the sassafras, the sweet-gum, the plane-tree, the 

 beach, the aralia, &c. The leaves of Protopliyllum Sternbergii have the 

 size and the facies of those of the catalpa, one of our finest ornamental 

 trees. Those of Menispermites obtusiloba, of Protospermum quadratum, 

 represent in the same manner some of the rarest shrubs, Menispermum^ 



