Climate of Middle Illinois. 7 



little founded species. But when we acknowledge the latter as " good " 

 species, then it ceases to be a monotype. Pentachaeta was, when Nuttall 

 proposed the genus, a monotype until A. Grray described a second species, 

 and with that as a variety, another monotype: Aphantochasta. So both 

 of them cease to be monotypes. 



Of eight other genera of the order Composita3, which Grisebach men- 

 tions as monotypes (in Vegetation of the Earth), only two : Whitneya and 

 Crocidium retain yet their monotypism: Actinolepris merged in Eriophyl- 

 lum, Oxyura in Layia, Coinogyne in laumea, Tuckermannia in Leptosyne. 

 Corethrogyne is now represented by three Hulsea by six species, and besides 

 two varieties. In the meantime not less than ten California monotypes 

 are proposed, the greater part, probably, waiting for the company of new 

 foundlings. 



These few examples, out of many, will show the value of monotypes 

 the more when we add the above mentioned Phryma, which is not only a 

 monotype genus, but after Schauer, even a monotype order, and does 

 exist in two so remote countries. 



In undisputed monotypes what else can we recognize but the isolated 

 remnants of an extinct plurality of forms, isolated by a row of geological 

 and climatological changes? Analogous examples are offered in Zoology, 

 when we compare the small number of recent ganoids with their abund- 

 ance in early geological periods. 



Comparatively few species of plants are distributed all over the surface 

 of our globe, of which a large proportion again proved to have spread by 

 migration, even in historical time. The great majority of species is 

 restricted to certain areas within certain limits that are defined by 

 climatical influences as heat, light, humidity, or by physical or chemical 

 qualities of the soil, or by geographical obstacles as are oceans, deserts or 

 high mountain ranges, which a species may be unable to pass over. 



The assemblage of species which, under the above mentioned influ- 

 ences, grow in a part of our globe, giving to the same its characteristic 

 physiognomy, we call the flora of that country and the area to which it, 

 as a whole, is restricted, we call a botanical province with subordinate 

 regions and districts. It is evident that political boundaries must be 

 excluded; the flora of a state may be quite different in its parts, f. i., in 

 Virginia the flora is different in the Atlantic slope, in the Alleghanies and 

 in the Western slope, and belongs, accordingly, to three different botanical 

 districts, as will be shown. 



To arrange the vegetable world geographically into natural provinces 

 and districts, the best guide will be the character of the landscape and the 

 statistic proportion of the species, genera and orders. Climate and nature 

 of soil will serve to elucidate the facts. 



Species, genera and orders, may be limited by lines, and so may be 

 determined the area of each, but it will not do for the complex of them. 

 For these lines will, in many ways, cross each other, and so the character 



