238 
IOWA ACADEMY OF SCIENCE Vor.. XXVIII, 1921 
Base. — The leaf base is also somewhat variable, though it 
is usually acute or sub-acute. It varies, however, to obtuse and 
rounded, but is never cordate. 
Apex. — The apex is most frequently somewhat acute, or sub- 
acute, but varies from short-acuminate to obtuse or rounded. 
Margin. — The margin is usually somewhat irregularly toothed, 
usually being serrate nearer the base and dentate or crenate to- 
wards the tip. It varies, however, from serrulate or crenulate to 
serrate, dentate, crenate, serrate-dentate, or crenate-dentate. 
Size. — The blade of the leaf reaches a maximum length of 9.2 
cm., but is usually 4 or 5 cm. long. The width reaches 4.9 cm., 
but more commonly it is about 2 cm. The petiole is usually about 
1 cm. long, but varies from .2 cm. to more than 2.0 cm. 
Habitat. — The habitat of the variety has been described as 
follows : sand-hills ; sandy soil ; stony hillsides ; gravelly 
slopes ; dry hills ; loess ridges ; hillsides and in dry soil ; dry 
prairie ridges ; dry prairie ; prairie ; prairie and forest 
border ; open thickets ; wooded bluffs 
In Iowa the variety is found most commonly on dry prairie 
knolls or ridges, but also occurs in prairie openings on partly 
wooded hillsides. 
The writer has collected this form in all parts of the state 
excepting the southeast quarter, but it is much more common in 
the western part of the state. Eastward in the state it is extremely 
local. 
Both the type and variety usually flower in Iowa in the third or 
fourth week of May, though a few plants have been found in 
flower as late as the . middle, and in one case even the end, of 
August. In any locality where both C. americanus and C. ovatus 
or the variety occur, the former will flower from three to four 
weeks later. Because of this circumstance, if for no other reason, 
the two species probably seldom, if ever, hybridize. 
While there may be some doubt as to the validity of this form 
as a species or variety, it is- ordinarily quite distinct, and the pe- 
culiarity of distribution makes it desirable to retain the name for 
ecological records. It is certain that the vast majority of Iowa 
plants belong to the variety rather than the type. 
The writer had the privilege of examining the extensive set of 
Ceanothus in the collections of the Missouri Botanical Garden, 
St. Louis, and he found that all the eastern and southeastern 
forms of this species belong to the type, while the western and 
southwestern forms belong to the variety puhescens. 
