ON THE CI1AIUCTEIUSTIC3 OF THE NORTH AMERICAN FLOJU. 561 



i-eckon sarracenia (of which the only extra- North American representative 

 is tropical- American), the melastomacea?, represented by rhexia ; passiflora 

 (our species being herbaceous), a few representatives of loasacese and 

 turaeracete, also of hydrophyllaceae ; our two genera of burmanniaceas ; 

 three genera of bsemodoracese ; tillandsia in bromeliacea? ; two genera of 

 pontederiacere ; two of commelynacea? ; the outlying mayaca and xyris, 

 and three genera of eriocaulonacese. I do not forget that one of our 

 species of eriocaulon occurs on the west coast of Ireland and in Skye, 

 wonderfully out of place, though on tbis side of the Atlantic it reaches 

 Newfoundland. It may be a survival in the Old World; but it is more 

 probably of chance introduction. 



The other set of extra-European types, characteristic of the Atlantic 

 North American flora, is very notable. According to a view which I have 

 much and for a long while insisted on, it may be said to represent a 

 certain portion of the once rather uniform flora of the arctic and less 

 boreal zone, from the late tertiary down to the incoming of the glacial 

 period, and which, brought down to our lower latitudes by the gradual 

 refrigeration, has been preserved here in eastern North America and in 

 the corresponding parts of Asia, but was lost to Europe. I need not re- 

 capitulate the evidence upon which this now generally accepted doctrine 

 was founded ; and to enumerate the plants which testify in its favour 

 would amount to an enumeration of the greater part of the genera or 

 subordinate groups of plants which distinguish our Atlantic flora from 

 that of Europe. The evidence, in brief, is that the plants in question, or 

 their moderately differentiated representatives, still co-exist in the flora of 

 eastern North America and that of the Chino- Japanese region, the climates 

 and conditions of which are very similar ; and that the fossilised repre- 

 sentatives of many of them have been brought to light in the late tertiary 

 deposits of the arctic zone wherever explored. In mentioning some of 

 the plants of this category I include the magnolias, although there are no 

 neai-ly identical species, but there is a seemingly identical liriodendron in 

 China, and the schizandras and illiciums are divided between the two 

 floras; and I put into the list menispermum, of which the only other 

 species is eastern Siberian, and is hardly distinguishable from ours. When 

 you call to mind the series of wholly extra-European types which are 

 identically or approximately represented in the eastern North American 

 and in the eastern Asiatic temperate floras, such as trautvetteria and 

 hydrastis in ranunoulaceoe ; caulopbyllum, diphylleia, jeffersonia and 

 podophyllum in berberidea? ; brasenia and nelumbium in nymphasaceas ; 

 stylophorum in papaveracea? ; stuartia and gordonia in ternstromiaceas ; 

 the equivalent species of xanthosylum, the equivalent and identical species 

 of vitis, and of the poisonous species of rhus (one, if not both, of which 

 you may meet with in every botanical excursion, and which it will be safer 

 not to handle) ; the horse-chestnuts, here called buckeyes ; the negundo, 

 a peculiar off-shoot of the maple tribe ; when you consider that almost 

 every one of the peculiar leguminous trees mentioned as characteristic of 

 our flora is represented by a species in China or Manchuria or Japan, and 

 so of some herbaceous legnminosas ; when you remember that the peculiar 

 small order of which calycanthus is the principal type has its other repre- 

 sentative in the same region ; that the species of philadelphus, or 

 hydrangea, of itea, astilbe, hamamelis, diervilla, triosteum, mitchella, 

 which carpets the ground under evergreen woods, chiogenes creeping 

 over the shaded bogs ; epigasa, choicest woodland flower of early spring ; 



1884. 



