GRANT—A MONOGRAPH OF THE GENUS MIMULUS 117 
some ancient and nearly related ancestors which are not now 
known, and in the course of evolution Eumimulus developed its 
complex floral structure and herbaceous condition. Simiolus, 
with its specialized zygomorphie calyx and its closely adherent 
placentae, has been derived possibly from some of the North 
American Eumimuli or from some member in the section Para- 
danthus. An extreme polymorphic condition is usually regarded 
as a recent development and signifies that evolutionary changes 
are continuing. As suggested elsewhere, the wide geographic 
distribution of Simiolus may be due to the minute seed being 
carried in mud on the feet of migratory birds.  Erythranthe is 
probably an offshoot of Tropanthus, as has already been asserted. 
Diplacus is the other shrubby section, and its zygomorphic 
calyx, irregular corolla, divided placentae, homogeneous species, 
and fairly wide distribution suggest a group that is somewhat 
ancient within this family. From it there is a gradual progression 
to herbaceous groups, most of which are annuals and confined to 
California. Within each group specialized forms may occur, 
each of these complex species being more or less isolated and usu- 
ally growing іп a much restricted area. Pseudoenoe with its pe- 
culiar corolla is presumably a recent offshoot of noe. Through 
M. latifolius and M. Congdonii there is a progressive transition 
from the long slender corolla-tube of (пое to the short funnel- 
form, campanulate, or bilabiate corolla of Eunanus. The species 
in Hunanus are closely related, many of them being of difficult 
discrimination and separated only by minor characters. Great 
variation and closely connected species indicate that the group 
is still in a process of evolution, and Eunanus therefore is probably 
of recent origin, though its corolla, in some cases, is quite primi- 
tive. Mimulastrum is descended from Eunanus, differing from 
it mainly in its characteristic corolla. Paradanthus, as stated 
earlier, is a collection of groups not necessarily related to one 
another and in all probability most of them have been derived 
from members of the other sections. 
GEOGRAPHICAL DISTRIBUTION 
The genus Mimulus offers very interesting problems in dis- 
tribution. Of the 114 species admitted in this monograph, 74 
