I20 BOTANICAL GAZETTE [AUGUST 
isolation has not been the primary factor in evolving these forms. 
That would hardly be argued by anyone. Isolation is no more a 
causal factor in variation or mutation than is artificial segregation, 
but like artificial segregation, as practiced by all breeders and experi- 
mental evolutionists, it.is of prime importance in preserving new 
variations or mutations. We saw at the outset that our method 
of investigation was not such as to divulge the real underlying 
factors that have brought about the different forms of Eriodictyon. 
It must be supplemented with experimental studies, but whether 
it is possible to conduct these experiments successfully remains 
a future problem. For the present it has been our aim to ascertain, 
first of all, what forms exist in the group selected, and so far as 
possible where and under what conditions they grow. With data 
of this nature available, the experimental work can be undertaken 
by anyone with a clearer conception of the problem, and with more 
likelihood of interpreting rightly the results of his experiments. 
ERIODICTYON Benth. Bot. Voy. Sulphur 35. 1844. 
Low shrubs with thin shreddy bark and persistent, alternate, 
toothed or rarely entire leaves, tapering at the base to a more or 
less evident petiole, or sessile in one species, of firm coriaceous 
texture. Flowers in a terminal, usually naked, panicle of scorpioid 
cymes. Sepals linear, not enlarged above. Corolla funnelform 
to nearly campanulate, pale or dark violet or white. Filaments 
more or less adnate to the corolla and included, usually hirsute 
and of irregular length. Ovary 2-celled by the meeting of the 
dilated placentae in the axis. Capsule first loculicidal then septi- 
cidal, thus 4-valved, each valve with a short beak and closed on 
one side by the adherent dissepiment or half-partition. Seeds 
brown or black, finely reticulate with ridges running lengthwise, and 
connecting them many cross-bars. 
A genus of eight species restricted to southwestern United States 
and adjacent Mexico, where they extend from southern Oregon 
and southern Nevada and Utah through Arizona and California 
to northern Lower California, but they belong essentially to the 
California element, and six of the species occur within and are 
practically confined to that state. 
