Blake — A Revision of the Genus Viguiera 25 
terms compressed and obcompressed used for achenes. For these 
conditions the word graduated seems preferable to imbricated, 
since the latter term is commonly used in botany to refer to later- 
ally overlapping organs of the same length. Some degree of lateral 
overlapping is of course so common in Compositae that not its 
presence but its absence requires comment. 
The terms employed in describing the texture, shape, and 
pubescence of the phyllaries are those in common use for leaves 
and require no special notice here. It may be well to note, however, 
that the term ribbed is here used to denote the presence of thick- 
ened, indurated, and usually pale costae in the lower portion of the 
phyllary, while vittate is used to denote the presence of thin linear 
glands. ; 
As the result of long-continued attempts at a natural classifica- 
tion of the species of Viguiera, I have been compelled to depend on 
involucral characters for the distinctions of nearly all the major 
subdivisions. Unfortunately it is very nearly impossible to con- 
vey in words a clear conception of differences in form and texture 
very noticeable when specimens are compared, and it has aceord- 
ingly seemed best to give, in addition to the key to sections based 
largely on involucral characters, an artificial key to all the species 
based chiefly on more easily recognized but less fundamental 
differences in leaf-form, pubescence, and so forth. The underlying 
principle of involucral variation in the genus — that of greater or 
less differentiation in the phyllary between a more or less indurated 
and ribbed base and an herbaceous or submembranaceous or sub- 
chartaceous apex — will become evident in the following descrip- 
tions of the chief groups. 
The subgenus Amphilepis (t. 2. f. 1-2) is characterized by its 
several-seriate involucre with the outer phyllaries herbaceous at 
least at apex (in two species dry and scarcely subherbaceous), and 
the inner especially in fruit with ampliated, somewhat elongated, 
and membranaceous or membranaceous-chartaceous rounded tip. 
The common V. excelsa well illustrates this type of involucre, 
which is peculiar to this subgenus. 
In the section Hypargyrea of Calanticaria the phyllaries of the 
slightly graduated involucre are firmly herbaceous with little evi- 
dent differentiation of base and apex, except for the slight ribbing 
below. The section Chloracra (t. 2. f. 3-10), aside from some ap- 
