458 SCIENCE PROGRESS. 



Bernissart beds are of special interest from the fact that by 

 far the greater number of plant fragments belong to ferns, 

 while cycads and conifers are barely represented. The 

 Wealden deposits, which fill up a deep canon cut through 

 the Carboniferous rocks at Bernissart, appear to be the old 

 sandy muds of a river which flowed through a marshy 

 region inhabited by the ungainly Iguanodons and carpeted 

 with a dense growth of ferns. 1 Some of the most important 

 Wealden districts are in the North American continent, 

 and the rich flora which they have afforded has recently 

 received exhaustive treatment at the hands of Prof. Lester 

 Ward. From Canadian rocks Sir William Dawson 2 has also 

 recorded species of Wealden plants, but it is in the United 

 States that the flora of this period is best represented. In 

 1889 Prof. Fontaine 3 published one of the United States 

 Geological Survey monographs on the " Flora of the Potomac 

 Series," and in this work there are described numerous 

 well-known European species of Wealden plants. It has 

 since been shown i that the Potomac formation— so named 

 by McGee in 1885 — includes rocks ranging in age from 

 Jurassic to well up in the Cretaceous system ; some of the 

 lower plant-bearing strata are undoubtedly of the same 

 geological age as the Wealden of Europe, and these have 

 furnished many interesting additions to our list of Wealden 

 species. Good evidence has recently been published of the 

 existence of a Wealden vegetation in Japan, 5 and from 

 Africa and New Zealand Wealden species have also been 

 recorded. 6 



We will first pass in review some of the best-defined 

 types of Wealden vegetation, and afterwards summarise the 

 chief features of botanical interest, neglecting such plants 

 as cannot be referred with certainty to a definite systematic 

 position. 



Alg/E. — The majority of the so-called algae from Wealden 

 rocks are of no botanical importance, and at best merely afford 



1 Dupont. 2 Dawson. 3 Fontaine. 



4 Ward (3). 5 Yokoyama, Nathorst (1). 



6 For reference to the existence of Wealden species in these countries, 

 vide Seward (1) and (2). 



