American Scientific Association. 297 



have these facts on the theories of the original distribution of 

 species ? Three different views have been advanced to explain the 

 distribution of the same plants on the globe. The first supposes 

 them to have originated in many different localities where they 

 now are found. This is the view entertained by Prof. Agassiz, 

 and on this theory these peculiar plants must have originated in 

 two distinct and widely separated districts. The second theory 

 refers the origin of each species, to one place, but allows some of 

 them to have been reproduced in other localities as exceptions to 

 the general law. The third refers each species to one place only 

 as its starting point, though not from one pair, necessarily, un- 

 less it be in the case of the higher plants. This was the theory 

 adopted by the speaker, although the facts already given as to the 

 plants found in Japan, at first seemed opposed to such an idea. 

 In explanation of those facts, he said the similarity of climate 

 between Japan and New England would not be sufficient. The 

 plants of western Europe are not like those of Oregon and Cali- 

 fornia, though the climate is. The idea that the seeds have been 

 carried naturally from one country to the other is not satisfactory. 

 He supposed the flora of this country to be older than the fauna ; 

 and that it dates back probably to the post-tertiary period. The 

 evidence of this last he based principally on the alleged fact 

 that fossilized specimens of our present flora have been found, 

 and referred to about the time of the drift period ; and he then 

 explained at some length his views as to the effect produced 

 on the vegetation by the changes in temperature during the 

 glacial period. Whatever dispute there might be as to this last 

 matter, the fact would not be denied that our present flora ap- 

 peared soon after that period. In the diluvial epoch the tempera- 

 ture in this latitude must have been much warmer than it now is ; 

 the temperate flora of the present day, then also in existence, 

 must have extended much further north, perhaps nearly up to the 

 Artie circle, and probably spread across from one continent to * 

 the other. Want of time prevented him from giving his views as 

 to why he adopted the third theory of the origin and distribution 

 of plants rather than the others ; he simply wished to-day to give 

 his views in explanation of facts seemingly opposed to it. 



DEVONIAN AND CARBONIFEROUS FLORA OF BRITISH AMERICA. 



Prof. Dawson of Montreal gave a summary of results which 

 he had obtained from the study of the land plants preserved in 



