1924] 
GRANT—A MONOGRAPH OF THE GENUS MIMULUS 109 
and hairy anthers being the chief characters used in differenti- 
atingit. Erythranthe was reduced to synonymy under Eumtimulus 
by Gray but later it was raised by Greene to sectional rank. Тһе 
вресіев in the section are closely affiliated and form a natural 
group. M. Nelson is somewhat aberrant with its unequal 
ealyx-teeth and short style. 
Simiolus was designated as a section by Greene, who expressed 
later the opinion that it should be raised to generic rank. In 
this section, he included not only the plants with personate 
corollas and inflated calyces but those with nearly regular corollas 
and prismatic calyces. As interpreted in this paper, Szmiolus 
is restricted to a closely connected polymorphic group of North 
and South American plants. In these the mature calyx is dis- 
tinctive in that it is much inflated and the lower teeth generally 
turn up and fold over the lateral teeth, nearly closing the orifice. 
The yellow corolla is personate with two prominent hairy ridges 
down the lower lip partly elosing the throat; the stamens are 
included and the placentae firmly united along their entire length. 
The vegetative characters show more diversity than the floral 
ones and are of value chiefly in separating the species. This 
section might have been derived from Eumimulus, the calyx 
diverging in the direction of zygomorphy or it might have been 
developed from some member of the section Paradanthus. Тһе 
primitive structure of the yellow-flowered M. moschatus of the 
latter section suggests a possible relationship between that 
species and the section Simiolus. It is possible that the poly- 
morphic condition may be a relatively late development. Sim- 
iolus is a very plastic group, the members responding quickly 
to environmental changes. Consequently there has been much 
confusion in the delimitation of the species and the synonymy 
has become rather burdensome. The early horticulturists found 
several of these species very satisfactory to experiment with, as a 
result of which many interesting garden varieties were pr oduced. 
In studying the species in the sections, there was found a large 
number which did not seem to belong to any of the well-estab- 
lished groups. These mostly comprised small closely allied asso- 
ciations which, however, were not sufficiently distinct to warrant 
ing placed in sections by themselves. They all have a more or 
