330 MR. F. N. WILLIAMS : REVISION 
are only mentioned by name in their place and are not described 
in the enumeration. In a few instances, however, where the 
original description is false, altogether misleading, or erroneous, 
and has been so copied into floras without correction, the species 
is described anew. By this exclusion of the description of 
species which have been long known, and which are therefore to 
be found in one or more general floras, the bulk of a systematic 
paper on a large genus is reduced. The species described are 
those of the last 50 years. After the citation or description, as 
the case may be, a few differential characters are given the more 
readily to distinguish the species from others in the same group, 
more particularly in subsidiary groups which include several 
species. Then are sometimes added a few critical or explanatory 
notes on the species and its varieties, where they may seem to be 
required. The geographical limits of the species are given, but 
not the full geographical distribution of each species, which 
would without advantage add considerably to the matter under 
the heading of each species; though for the less common ones 
the habitat is given in the usual way. The last item under each 
species is the iconography and synonymy. The iconography, 
verified by comparison with authentic specimens, is as full as 
possible, every plate with which I am acquainted being cited, 
excepting only those which are obviously bad or misleading. In 
every case the date of publication is added to the reference cited 
for the species: not, however, that priority of date in the 
currency of names is of so much importance as compared with 
the convenience of retaining long-established names, but for 
ready reference. The synonymy of Alsine, in so far as it does 
not concern Arenaria in its restricted sense, is not dealt with. 
A few words of explanation as to the subdivision into sub- 
genera may be necessary. Two-thirds of the number of the 
species, viz. 111, belong to the typical subgenus Huarenaria, 
which includes species in which disk-glands are not evident or 
are quite inconspicuous, and the capsule splits by six teeth or 
valves. In the subgenus Eremogoneastrum the disk is lobed, and 
the ten glands alternate with the stamens; all the species 47e 
narrow-leaved, with the basal leaves usually long and grass-like. 
In the subgenus Pentadenaria (so called in allusion to the a 
glands) the disk is expanded into five prominent glands, eac 
bearing a stamen, so that the ten stamens are distinctly du^ 
in two series. The species of the subgenus Dicranilla are à 
