280 DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 
variety, subspecies, form, or lusus, by one or more very able and experienced botanists, 
some of them by many. Furthermore, it is curious to observe how much the botanists of 
each country do to a considerable extent agree amongst themselves as to the specific identity 
or difference of the same forms — the Scandinavian agreeing with Pries, the German with 
Koch, and the American with Hooker's 'Mora Boreali- Americana '; also to observe, 
that in all these cases the authors I quote are independent observers, and not copyers or 
followers. I think this fact indicates that the same plant presents a different aspect (pro- 
bably obliterated in drying) in each country. This observation is consonant with what we 
know of the tendency of all species to run into local varieties in isolated areas, which va- 
rieties are often appreciable to the eye or to the touch, but are not expressable by words. 
Of the 762 species enumerated, I have compared arctic or boreal specimens of all but a 
few which I have indicated in the appended notes, and in most cases I have compared 
specimens from all the southern areas indicated ; but I do not pretend to have made such 
a critical study of all the grouped species, or of all those belonging to difficult genera (as 
Draba, Poa, &c), as to enable me to say that I have given all their distribution, or satis- 
fied myself of all their affinities and differences. There are, on the contrary, fully 60 
genera out of the 323 arctic ones enumerated, each of which requires careful monograph- 
ing, and months of study before the limits, systematic and geographical, of its common 
European species can be ascertained. In two of the largest and most difficult of these I 
have been indebted to others ; namely, to Dr. Boott, who has revised my list of Carices, 
and to Dr. Andersson of Stockholm, who has drawn up that of the Salices : each has ex- 
tensively modified the conclusions of his predecessors in arctic botany ; quite as much or 
more so than I have done in any genus, and I have every confidence in their judgment. 
Colonel Munro has twice revised the list of grasses with a like result. In these impor- 
tant genera, therefore, the groups express the opinions of these acute botanists as to the 
limits of the species. 
With regard to the probable completeness of our knowledge of the flowering plants of 
the arctic zone, I think it is pretty certain that there are few or no new species to be 
discovered. The collectors in the numerous voyages undertaken since 1847 in search of 
the Franklin expedition have not added one species to the flora of the Arctic American 
islands, and but one to that of Arctic Greenland. The Lapponian region is, of course, as 
well known as any on the globe ; but further east, and especially in Arctic Siberia, much 
remains to be done ; not perhaps in the discovery of new plants, but in ascertaining the 
southern limits of various Siberian ones that probably cross the arctic circle. Of Arctic 
Continental America the same may be said. 
The method which I adopted in finally arranging the materials for geographical purposes 
was the following. I took Wahlenberg's ' Flora Lapponica,' Fries' ' Summa Vegeta- 
bilium Scandinavian' Ledebour's < Flora Eossica,' Hooker's « Flora Boreali- Americana,' 
and Lange's ' Plants of East Greenland,' which together embrace in outline almost every- 
thing we know of arctic botany, geographical, systematic and descriptive. I put together 
from these all the matter they contained, and arranged it both botanicaUy and geogra- 
phically into a « Systema,' which I studied with an Admiralty north circumpolar chart ; 
and by this means arrived at a general idea of the position and extent of the centres of 
