616 Evans: REPORT ON THE HEPATICAE OF ALASKA 
The occurrence of Atlantic species and of Hawaiian species in 
Alaska is of much interest, although it is impossible to point out 
at the present time what its significance may be. Such a species 
as Pleurozia purpurea, which is evidently a stable species of great 
age, may originally have been much more abundant and more 
evenly distributed than at the present time. Then, through the 
encroachment of other species at various portions of its range, it 
may have become restricted to the isolated regions where it is now 
found. This might explain the occurrence of the species in both 
western Europe and Alaska and its absence from the intervening 
regions. There is little evidence, however, that the volcanic 
Hawaiian Islands were ever connected with either North America 
or with the mainland of Asia, so that it is difficult to account for 
any close connection between the plants of the Islands and those of 
Alaska or the Himalyas. 
The most remarkable species in the present collection came 
from southeastern Alaska, and it is probable that many other 
Hepaticae remain to be discovered in this interesting region. 
Such a species as Scapania planifolia (Hook.) Dumort., for ex- 
ample, which often grows in company with Pleurozia purpurea in 
western Europe ought surely to be expected, especially since it 
occurs also in the Himalyas and in the Hawaiian Islands. And, 
in view of the presence of the very rare Bazzania Pearsoni in 
Alaska, other Atlantic species of circumscribed range may come 
to light. In any case southeastern Alaska is recommended to 
collectors as an unusually favorable region for careful study. 
SHEFFIELD SCIENTIFIC SCHOOL, 
YALE UNIVERSITY 
Explanation of plate 21 
Plagiochila alaskana Evans. 1. Part of a stem with perianth, antical view, 23. 
2. Part of a stem with perianth, lateral view, X23. 3. Leaf spread out, X23. 4- 
Bract spread out, X23. 5. Cells from the middle of a leaf, X300. 6. Marginal 
tooth of a leaf, 300. The figures were all drawn from the type wipe 
Plagiochila Fryei Evans. 7, Leaves spread out, X23. eal. hom the 
middle of a leaf, X300. The figures were all drawn from the aati specimen. 
