88 MISSOURI BOTANICAL GARDEN. 
stigmas. Opposite each lobe is a group of staminate 
flowers, indefinite in number and subtended by minute 
bracts which partake more or less of the characters of the 
lobes. The pendulous seeds are smooth or variously 
sculptured. The embryo is pendent and the cotyledons are 
ovate and often cordate. The measurements of seeds are 
exclusive of the caruncle. The caruncle, which is usually 
present, occupies an oblique ovate or triangular space about 
the funiculus. The raphe forms a line from this to the 
chalaza at the lower end where there is often a circular 
depression. 
The small size of the flowers and the complicated struc- 
ture of the inflorescence make the study of the genus 
somewhat difficult; and the great variability of the leaf 
and involucral characters has led some authors into error. 
The method of branching and the phyllotaxy offer much 
aid in classification, as also does the shape of the glands 
and lobes within certain limits. The seeds give the best 
specific characters, being very constant in shape and mark- 
ings and usually in size, except in the perennial species of 
the subsection Hsulae, where the seeds of several species 
differ but little. 
A list of the specimens seen is given at the end of each 
description. Other important localities mentioned by other 
authors are given at the end of this. 
I have intended to cite all the synonyms of species de- 
scribed, the most important American publications, and some 
of the better illustrations of such as have been figured. For 
the most part, the Madison rules for citation have been fol- 
lowed. The illustrations are cited after the other works, 
and preceded by a dash. Some of the more important 
general works are indicated at the end of the revision; for 
other literature the reader is referred to these, especially ~ 
to the first three, where more complete bibliographies are 
given. 
In the diagram of relationships, Table A, the length of 
4 
