explorations still seems to rest over the Alaskan Flora and to prevent it from becoming known to the botanical world.
        After the close of the gold rush period some years after the beginning of the present century, a new period of botanical exploration in Alaska and Yukon sets in. During this last period several important botanical collections were made practically every year, and the material has given a better and better, and now a fairly complete picture of the total flora. The interior, which up to the very last remains still not very well known, must yield up more and more of its botanical secrets. Geologists, teachers, agronomists, foresters, officials, tourists and professional botanists are contributing on an increasing scale to botanical exploration. Among professional botanists, A. S. HITCHCOCK visited Alaska and Yukon in 1909 in order to study the grasses; in 1913-19 R. GRIGGS investigated the change in the vegetation caused by the great eruption of the Katmai volcano; A. EASTWOOD obtained large collections of trees and shrubs in Yukon in 1914; J. P. ANDERSON collected during the years 1914-40 a large botanical material from most parts of Alaska; during 1916-35 W. S. COOPER carried on ecological studies in Glacier Bay, especially of the flora arising on the virgin soil formed at the regression of the Muir glacier; M. O. MALTE collected in Yukon; the brothers PORSILD obtained valuable collections in the interior of Alaska and on Seward Penins. in 1926; Miss Y. MEXIA worked at Mt. McKinley park in 1928; Prof. SETCHELL visited Yukon and the interior of Alaska in 1932 in order to collect especially Salix specimens; In 1932 the present author, assisted by Mr. J. W. EYERDAM, investigated the Aleutian Islands, hitherto not very thoroughly explored botanically, and Dr. A. NELSON obtained large collections in Mt. McKinley Park in 1939. In 1937 the present author published a study of the Arctic and Boreal phytogeography under the title »Outline of the history of Arctic and Boreal Biota during the Quaternary Period».    I n   t h i s   w o r k  a l l  p l a n t s  a t  t h a t  t i m e  k n o w n  t o  h i m  t o  o c c u r  i n  A l a s k a   a n d  Y u k o n are enumerated in groups, the approximate geographical area of which are given in maps.
        It may be said that in 1940 the body of botanical material accessible in the museums and in the 200 or so scientific papers dealing with the flora and vegetation of our area is so comprehensive that the picture it gives is, on the whole, a correct one. Subsequent additions will hardly change its main features. For the present no single work makes this knowlegde available to science. It must be gathered from the very scattered and often not easily accessible literature and from