GEOLOGICAL SURVEY OF THE TERRITORIES. 315 



No species of Glumacece is as yet known from the Cretaceous forma- 

 tions of this continent, but from uncertain remains, knots separated 

 from the stem, and a piece of a stem referable to the genus Arundo. As 

 Glumacece and GyperacecB are hirgely represented in the Tertiary, we 

 may expect to find types of these orders of plants in some strata of the 

 Upper Cretaceous, their distribution being local, as remarked formerly. 

 Per contra, the Cretaceous has already typical representatives of the 

 essential sections of the Gymnospermce, as they are seen later in the Ter- 

 tiary and now in our flora. The Guj)ressinem are represented by Glyptos- 

 trohis f/racillimtiSjJjsqx.', theAMetineoe, hy Araticaria (?) spathulata, Newby, 

 Sequoia formosa, Lsqx., a cone of Abietites described as Fterophyllimi, (?) 

 Lsqx., all these from Nebraska and Sequoia BeiclienhacM, Heer, from Mon- 

 tana. These are followed in the Tertiary by a number of forms of Taxo- 

 dium, Glyptostr obits, Sequoia, &c., all repeated without striking variations 

 in our flora. Sequoia is well represented in the Miocene of Europe ; but 

 this genus has disappeared from its flora, as also from our northeastern 

 American flora, being still distributed in California. The type of our 

 Abies appears to be Araucaria spathulata, named above, a form referable 

 to three species of Abietites, described by Dunker from the Quader- 

 sandstein of Blankenburg, and which, altogether, may represent a single 

 species. As yet we have no remains of Pinus, neither from the Creta- 

 ceous nor from the Tertiary. Heer has, however, described two species 

 from the Cretaceous of Greenland, and twenty-four species from the 

 arctic Tertiary. That they have not been found yet in the North 

 American measures, is merely the result of the geographical distribution 

 of the species of this genus. A remarkable group of the Taxinece, repre- 

 sented already in our Cretaceous by one species of Phyllocladus, and in the 

 Lower Tertiary by a Salisburia, is out of our present flora. The species 

 of the first genus inhabit New Holland and Tasmania ; the other has only 

 one living representative species in Japan. Nothing can be said on the 

 causes of migration, and extinction of vegetable types. As Australia has 

 now animal species analogous to those of the Cretaceous, it would not be 

 peculiar to find there also the same kind of analogy for plants. Species, 

 especially of conifers, disappear without appreciable causes, as some 

 of them are now dying out at our time ; the cedar of Lebanon, the pine 

 {Pi7ius cembra) of the Alps, the giant trees of California, {Sequoia, &q.) 

 That our climate is well appropriate to the vegetation of Salisburia 

 adiantifolia is proved by the result of its culture. There is in the row 

 of trees bordering the Common of Boston, a splendid representative of 

 this species, with a trunk about one foot in diameter. It has never been 

 sheltered, and is there mixed with elms and other indigenous species. 



But the conifers do not furnish the essential characters to our present 

 arborescent flora. Most of the trees of our forests belong' to the first 

 division of the dicotyledonous plants, that of the apetalous; the sweet- 

 gum, the willow, the poplar, the oak, the beach, the elm, «fcc., are of 

 this kind. 



Already one species of Liquidambar is known from its remains in the 

 Cretaceous, L. subintegrifolius, intimately related to another species, L. 

 gracile, of the Lower Tertiary of the West. Both are remarkable for the 

 entire borders of the leaves; but for this, the form of the Cretaceous leaf 

 is similar to that of L. styracijina, our sweet-gum. Two species are also 

 represented in the Miocene of Europe. Of the poplars, already seven 

 species have been described from the Cretaceous of Nebraska. The 

 types of our actual species are marked there already, and more still in 

 the species of the Tertiary, (21,) some of them identical with those of 

 the same formation of Europe. The willows have five species in the 



