24 Contributions from the Gray Herbarium 
Involucre. Although the importance of involucral characters for 
systematic purposes has long been recognized, very little attention 
is usually paid to them in descriptions of new species, while the 
minuteness and relativity of the differential characters involved 
often render their intelligible description a difficult matter for even 
the most painstaking. The variations in the phyllaries ! fall into 
six chief categories: (1) in absolute number; (2) in arrangement 
horizontally (i. e., in one, two, or more series, without reference to 
eight); (3) in arrangement vertically (i. e., in series of equal or 
unequal lengths); (4) in shape; (5) in texture; and (6) in character 
and amount of pubescence and glandularity. The first of these, the 
absolute number of the phyllaries, is in Compositae at large a char- 
acter of relatively slight importance, except in some groups with 
but a single main row of phyllaries, where it is often of much signifi- 
cance for the distinction of species. In general, however, because 
of the usual difficulty of obtaining precise information on this 
point from the mounted specimen this matter is passed over 
lightly in work on Compositae, and rightly so. It is otherwise with 
regard to the arrangement of the phyllaries, when as is usually the 
case they are in more than one row. In most cases the phyllaries 
are successively longer centripetally, giving what has been called 
an “ imbricate ”’ or “ seriate ”’ arrangement, the former term per- 
haps having been reserved for those cases in which the inequality 
was very pronounced. For the sake of definiteness, it seems ad- 
visable to use the expression “ n-seriate ” to describe an involucre 
whose phyllaries are in n rows, without prejudice to their height; 
to be qualified, in the normal case of centripetal increase in length, 
by the word graduated (Latin gradatus), the rarer case of centrifugal a 
increase in height being. called obgraduated, in conformity with the — 
! This term is here eo ee for the involucral leaves, ape S 
use. e often used “scale” or “ br ese 
the best of those now at 
to perm 
ea and the term “ phyllary ” atin hyllarium, from puddapwv, @ 
r oe 
8c. 
; ualifying 
use without some q inttle : | 


