1921] JOHNSON—VIRGIN SOIL 311 
sional at edges of valley), Ageratum conyzoides L. and A. houstoni- 
anum Mill. (rare), Mikania scandens L. (Wild.) (infrequent), 
Eupatorium triste DC. (few), Baccharis scoparia sp. (a dozen or so), 
Pluchea adorata L. (Cass.) (not infrequent), and Bidens incisa Ker. 
(frequent). All of these plants, with the possible exceptions of the 
Pilea and Bidens, were far less abundant than any of the four 
species mentioned in the preceding paragraph. Most of these 
fifteen plants are also smaller species, which likewise makes them 
less conspicuous in the vegetation of the valley. The Duranta, 
Solanum, and Baccharis are now as large as the species of Vernonia, 
but not asnumerous. The climbing forms Philibertella, Maurandia, 
and Mikania of course are rather long, having already reached and 
spread over the tops of the largest plants near them. Many indi- 
viduals of these fifteen species, as for example those growing in 
unusually dry situations, were dwarfed, and thus showed by their 
stunted form that they were not finding optimum conditions in 
the sterile soil and dry exposed situations afforded by the gravelly 
floor of the valley. 
It is to be noted that, contrary to the accepted rule for invaders 
of new soil areas, as stated by WARMING,‘ the plants now established 
in the Cascade Valley are not mostly annuals or biennials. Instead 
they are chiefly perennials, and in fact shrubby or half-shrubby 
ones. Although this is true, it is to be noted also that not one 
arborescent form has yet been found, unless some of the young 
plants of Piper seen should prove to belong to one of the more tree- 
like species of this usually shrublike genus. 
In this area of virgin soil there are present right through the year 
all of the climatic factors, such as moisture, heat, and light, that 
are needed for the production of a rich vegetation. This is evident 
from the dense forest that has developed in the adjoining valleys and 
even on the hills immediately overhanging the Cascade Valley 
itself. It was for these reasons that the writer was rather surprised, 
on revisiting this valley in 1919, at the slowness with which it is 
being recovered with vegetation. He was surprised not only at the 
relatively small number of new individuals, but especially at the 
very small number of species that had established themselves in the 
4 Oecology of plants. p. 356. 1900. 
