species. All authors agree that the family is to be grouped in the 
series Choripetalae, plants which have the corolla, when present, 
made up of separate petals, but in the Crassulaceae we have many 
types in which the petals are more or less united, in some nearly 
up to their tips, into a gamopetalous corolla, thus showing numer- 
ous exceptions to the general scheme of plant classification. The 
genus Gormania Britton, made up of several West American 
species with the habit of some Sedams, which Mr, Praeger 
-includes in Sedum, is an interesting natural group with partly 
united petals, the type species, G. Watsoni Britton having, on 
this account, been originally described as a species of Cotyledon, 
a genus with definitely gamopetalous corolla. 
Mr. Praeger includes the Linnaean genus BJwdiola in Sedum, 
following many other authors. But Rhodiola differs from Sedum 
by having staminate flowers on one plant and pistillate on 
another, and the typical species composing it have rather well- 
marked habital features, forming a very natural group ; he has 
sought to break the genus down by associating with these a 
number of other true Sedums of somewhat similar habit, among 
them our Rocky Mountain Sedum rhodanthum, the type of the 
genus Clementsia Rose, its characteristic spike-like flower cluster 
marking it off sharply from true Sedums, agreeing in this char- 
acter with Sedum Semenovii of Turkestan. 
The well-defined Mexican genus Cremnophila Rose, is taken 
into Sedum by Mr. Praeger, but it does not properly belong there 
as Dr. Rose has conclusively pointed out, although he first 
described this very interesting plant as Sedum nutans. We have 
had it under observation at the New York Botanical Garden since 
1905, where it has flowered every year, and the illustration of it 
published in 'Addisonia' plate 25, shows that it is quite different 
from any true Sedum. 
Sedastrum Rose, another Mexican genus merged by Mr. 
Praeger in Sedum, is another natural group of species. 
The very careful and painstaking indentification of species 
which marks Mr. Praeger 's long-continued studies of these plants 
is a noteworthy contribution to botanical and horticultural 
science; he has cleared up many points which were obscure and 
his critical descriptions of the species are admirable ; his illustra- 
tions of the plants studied are most helpful and he will have the 
gratitude of all students of the family. It is, naturally, pleasing 
to us to have been of some service in his mvestigation by sending 
him cuttings from many plants in our collections at New York 
and at Washington, which he has made use of in his descriptions 
and illustrations. 
Mr. Praeger has fallen into error, however, in his identifica- 
tion of Sedum oaxacanum Rose, a Mexican species which he rede- 
scribes as S. polyrrhizum Praeger. 
N. L. Britton. 
104 
