PORTULACES, AND THEIR ALLIES. 69 
the most puzzling to define among the whole range of Caryo- 
phyllee. Originally characterized by 5 sepals, 5 entire petals, 10 
or rarely 5 stamens, and 3 styles, it was subsequently found that 
these numbers were liable to variation, that in some species the 
petals were excessively reduced or disappeared altogether, in others 
the styles were frequently reduced to 2, and that characters de- 
rived from number could no longer exclude the Linnean genera Cher- 
leria, Minuartia, Mehringia, &c., whilst on the other hand the cap- 
sule appeared to afford means of dividing the whole group in a more 
definite manner. Accordingly the greater number of species have 
been distributed iuto three principal genera, Arenaria, Mahringia, 
and Alsine ; and at least ten others have been proposed, chiefly for 
individual species in which some striking peculiarity has been ob- 
served. But a further consideration of the results has convinced 
us that the three large groups are far too unnatural to be con- 
sidered as more than artificial sections; and that the prominent 
characters of the monotypic genera differ but in degree from those 
exemplified in other species. Spergularia alone forms an excep- 
tion, and is generally admitted ; for although the presence of sti- 
pules is its only positive character, its affinity is evidently much 
more with Spergula than with Arenaria. 
Arenaria itself is limited by Fenzl and others to those species 
in which the capsular valves are more or less deeply divided so as 
to become double the number of the styles, and the seeds are 
without any strophiola ; Mehringia has a similar capsule, but the 
seeds are smooth and shining, with the funicle expanded into a 
strophiola; and Alsine has the capsular valves entire, of the same 
number as the styles. These characters are tolerably definite, and 
not liable to much variation in the same species, and therefore excel- 
lent for sectional distinction. But when it is considered that A. 
Ledebouriana, A. Roylei, and their allies are in Arenaria, whilst 
A, laricifolia, A. pinifolia, &c., are in Alsine,—that A. pubescens, A. 
hispida, and A. diffusa, Ell. (A. nemorosa, H. B. et K.), go toge- 
gether in Arenaria, whilst A. trinervis, A. bavarica, and A. lateri- 
Jlora are in Meehringia,—that A. polygonoides is in Mehringia and 
A. procumbens in Alsine (or in Rhodalsine of Gay),—that A. mo- 
desta, A. conimbricensis, &c., are retained in Arenaria, whilst all 
their nearest allies belong to Alsine, and that the alpine ezspitose 
species are also distributed between the two, these sections can 
scarcely be considered as better genera than the old Linnean one. 
The characters upon which the smaller, mostly monoty pic ge- 
nera Cherleria, Siebera, Minuartia, Dolophragma, Triplateia, Gouf- 
