1915] SMILEY—LAKE TAHOE REGION 277 
In the Tahoe region this Transition flora covers approximately 
25 per cent of the total area, which is equivalent to saying that by 
far the larger part of that flora lies below the region considered in 
the present report, and we are here dealing with that fraction of 
the total which has been called Upper Transition, a flora showing 
more relationship to the life zones above than to those below. It 
is this fact of alliance with strictly alpine and subalpine floras that 
requires us to consider it here. 
The Upper Transition forest, as of all the higher zones, is ex- 
clusively a coniferous forest; what few arboreal or arborescent 
angiosperms are present are only found close to streams or lake 
shores and hence are to be regarded as members of the stream bank - 
association. This Transition coniferous forest is formed by Abies 
concolor, Pinus Jeffreyi, Pinus ponderosa, Libocedrus decurrens, 
and Pinus Lambertiana, in frequency in approximately the order 
named. The forest growth is dense in but a few favored localities, 
as on the floor of the ancient Fallen Leaf Glacier at the south end 
of Fallen Leaf Lake. Generally the trees are scattering and indi- 
vidual trees relatively small compared to the average size of the 
Same species on the western slope of the Sierras. The white fir 
alone maintains its average form. The sugar pine is scarce, since 
in the district the moderately moist rich flats frequented by this 
tree commonly lie above its range. The yellow pine is a common 
tree about Tahoe and northward to Truckee, but is dwarfed in 
size, and appears excessively parasitized by Arceuthobium occiden- 
tale. At the south end of the lake the nearly allied species Pinus 
Jeffreyi makes with Abies concolor two-thirds of the forest cover. 
Sa rule, the woods away from the streams are free from under- 
brush, the surface vegetation consisting of low perennials mainly, 
such as Corallorhiza Bigelovii, Pyrola asarifolia incarnata, Ptero- 
Spora Andromeda, Pedicularis semibarbata, Antennaria argentea, 
Antennaria Geyeri, and in sunny glades Balsamorhiza sagittata, 
Erigeron divergens, and Madia exigua. 
Next to the forest in importance in the general aspect of the 
Transition flora comes the stream bank association, which advances 
up all the water courses, cutting the coniferous forest into isolated 
fragments. In this stream bank vegetation Populus trichocarpa, 
Populus tremuloides (there is a charming aspen grove on the low 
