(187 ) 
Senecio lugens Richards. Above Fort Selkirk (Tarleton) ; 
Dawson (Williams). 
Senecio saliens Rydb. Bennett City (Williams). 
Senecio discoideus (Hook.) Britton. Dawson (Williams) ; 
Fort Selkirk (Tarleton). One of the specimens with rays. 
Saussurea nuda Ledeb. Walker Gulch (Williams); be- 
low Stewart River (Tarleton, 168; 168b). 
These specimens are the same as one of S. alpina remoti- 
flora Hook., received by Dr. Torrey from Dr. Hooker, and 
preserved in the Columbia University Herbarium. This 
variety of Hooker is referred by Ledebour in Flora Rossica 
to his S. muda. It differs, however, in its much narrower 
leaves, and may be a distinct species. 
The Oaks of the Continental Divide north of [lexico. 
> By P. A. RYDBERG. 
All thas of Colorado have lately been referred to ie 4 
two species, Quercus undulata and 2. Gambeliz. Mr. a K: 
Vreeland and t,spent a portion of last summer in thegouthern 
part of that Staté yand i in studying the oaks in the field we 
came to the conclusion that those of the regions visited must 
belong to five or six species. The differenées were manifest 
even early in the sprifg when the Jeéaves unfolded. In 
the Cuchara valley aroun ‘La Veta sefub- oaks are very com- 
mon. They usually grow in Marg ge“Clumps often 20-30 m. in 
diameter. The roots of several of the species grow hori- 
zontally, close below the surface ‘of the ground and send up 
numerous shoots. These, aks also fr uit very early, often be- 
core they are a meter high ; therefore, when a young oak has 
started in a place, there soon grows uf, around it a whole 
colony of still y ounger ones. As the youngést on the periphery 
of the clump have more light and air, theyigrow faster and 
soon overtake those in the center, and sack, ae the small 
trees of the colony quite often have the same héight (1-5 m.) 
as if they were trimmed with a gardener’s clipper. In rocky 
er 
