126 UNITED STATES GEOLOGICAL SURVEY— TESTIAUY FLORA. 



APETALyE. 



AMENTACE^. 



MYRICACE^. 



MYRICA, Linn. 



This genus is now represented by about forty species, distributed over 

 the whole world, with the exception of Australia. The continent of America 

 has the largest number. Besides seven species belonging to the flora of the 

 United States, ten others inhabit Mexico and the Pacific coast as far south 

 as Peru. In Africa, the Cape of Good Hope has nine and Abyssinia one. 

 Asia has six species between the tropic and the equator, two species being 

 ascril)ed to Java. Cuba has two, Japan one, and Europe one, Myrica gale, 

 indigenous also in this country. A peculiar section of the Myriccs, Comp- 

 tonia, which had many representatives in the Tertiary floras, has only one spe- 

 cies living, M. Comptonia, D. C, the well-known Sweet Fern, which exclusively 

 belongs to the Atlantic slope of North America. The present distribution 

 is worth remarking in comparison to what is known of the genus in the geo- 

 logical times, in order to come, if possible, to the solution of the question 

 referable to the origin or dispersion of vegetable types. 



The Cretaceous flora of North America has two species of Myrica recog- 

 nized by their leaves, and one by seeds, the latter referable either to one of the 

 two first species or representing a third. In Europe, two species also have been 

 described by Heer from the Quadersandstein of Quedlinburg, Germany, and 

 a third from the Upper Cretaceous of Greenland. Therefore the origin of 

 the genus is positively recorded in the flora of the Cretaceous, and at this 

 period its presence is about equally indicated in Europe and in this country. 

 But ascending higher in the geological ages, we find forty species of Myrica 

 described from the Lower Tertiary of Europe, half of them in the Eocene, 

 the other part in the Paleocene, and more than forty species in the Miocene. 

 From the Eocene, or Lower Lignitic, of the United States, we know as yet 

 only two species of this genus, one of which is still of doubtful reference; 

 and from the groups of Carbon and Evanston, considered as Upper Eocene 

 and Miocene, we have none. It is only in the fourth group, that of the 

 Parks and of Green River, that we find the genus represented by a propor- 

 tionally large number of species, twelve, six of which are referable to the 

 section Comptonia, -whwh/^n the European Tertiary, has twenty-three species. 



