MICHIGAN ACADEMY OP SCIENCE. 
205 
KEY TO THE SPECIES AND VARIETIES OF SOLIDAGO IN 
MICHIGAN. 
BY CHAS. II. OTIS. 
The following key is based upon a. study of several hundred speci- 
men sheets, principally from the University of Michigan and Michigan 
Agricultural College herbariums, supplemented by field work with grow- 
ing specimens. The key is a result of some work along certain sys- 
tematic lines directly under the supervision of Prof. H. A. Gleason. 
Those who have had occasion to use the keys for identification of 
Solidago found in the manuals in common use must have been annoyed 
by the “unusableness” of such keys. The genus Solidago is not an 
easy one at best, there being so many gradations between one species 
or variety and another. While it is realized that the present key, in 
common with any other kev, no matter how carefullv it has been 
worked out, will not serve to identify absolutely any and every indi- 
vidual which may be found in the state, it is thought that it will quickly 
and easily distinguish the vast majority of specimens in the field. No 
explanation of the manner of using the key seems necessary, except to 
state that it is dichotomous throughout and that there are only three 
large types recognized. The first is characterized by clusters of flower 
heads in the axils of ordinary foliage leaves, the second by rounded or 
flat-topped inflorescences and the third by cylindrical or pyramidal in- 
florescences. These three types can be easily recognized with a little 
practice, when the minor divisions of the key can be handled with little 
difficulty. The habitat notes in parenthesis have been added solely to 
aid in the determinations and are not strictly a part of the key. The 
scientific names follow the usage of Gray’s Xcir Manual of Botany , 
seventh edition. 
a. Heads chiefly in clusters or short racemes in the axils of ordinary 
foliage leaves, or the upper compacted into a leafy thvrse termi- 
nating the stem. (Compare with the thyrsoid type in bb under 
a a) . 
b. Stem and both sides of the leaves essentially glabrous, 
c. Basal leaves abruptly narrowed to winged petioles, 
d. Involucre 2-5 mm. long, its bracts broadly ovate, obtuse; 
rays 3-4; achenes very pubescent, (moist woods) 
lati folia. 
dd. Involucre 8-12 mm. long, its bracts linear, acute; rays 8-10; 
achenes glabrous, (shore of Lake Superior) 
/S', macropliylla. 
cc. Basal leaves not abruptly narrowed to winged petioles. 
d. Lower leaves lanceolate, acuminate, thin, sharply serrate; 
achenes pubescent. 
e. Stem usually simple; heads few, in very small clusters, 
(rich woods) 8. caesia. r. axillaris. 
