44 VARIATION IN ASTER 
out the body of the tube I do not find, though relied on by 
Cassini as a marked character for his A. /wssiez, nor do I find 
i equal disk-lobes, such as he described, and I surmise that these 
two points in his description relate to an accidental, not a regular, 
condition. 
Disk-flower form is very characteristic throughout a species ; 
bell-shaped usually, narrowly so in A. Claytoni, moderately in A. 
divaricatus, broadly in A. carmesinus and A. rupicola ; in all these 
the stalk of the disk-flowers is abrupt. They are funnel-form or 
gradually narrowed into the stalks in A. nobilis, A. Jussiet and 
close congeners. Disk-lobes are erect in the latter examples, but 
are widely spreading in most other species. 
Achene variations are few among the Biotian species; usually 
there is no pubescence; in certain species, as A. Clayton, scanty 
pubescence often occurs, but almost as often does not, or is gone 
at maturity ; in A. furcatus pubescence over the achenes forms a 
marked character. 
Receptacle characters I do not find very discriminating, for the 
reason that through so large a number of species their receptacle 
remains the same, foveolate (areolate with a little firm, thin, 
greenish-white raised border around each areola), and fimbrillate 
(having this border cut into five or more lobes). "When I was first 
delighted with the beauty presented by this character, in examin- 
ing A. divaricatus curtifolius specimens at Washington, D. C., in 
1889, I supposed it diagnostic of that particular form. Later I 
found it extending widely, if not continuously. Nees made much 
of this character. Asa Gray remarked, on the other hand, that he 
could make nothing of it, I think because working with herba- 
rium material instead of living plants ; and he may also have con- 
cluded that little difference is shown in different species. There is 
this difference, however, that seems to show occasionally, that some 
forms lack the fimbriae, some have but very shallow raised borders, 
and some have an additional central tubercle in each areola, bear- 
ing the base of the achene. 
Annular thickening on the summit of the achene. Such a 
thickening forms a whitish ring uniting the summits of the verti- 
cal striae in many species, notably the Curvescentes. In some it is 
much stronger than others, and in some it is decurrent between 
