(i87) 



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. alfina remoti- 

 Jlora 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. nuda. It differs, however, in its much narrower 

 leaves, and may be a distinct species. 



The Oaks of the Continental Divide north of Mexico. 



By P. A. Rydberg. 



All the oaks of Colorado have lately been referred to only 

 two species, ^iiercus undulata and J^. Gambelii. Mr. F. K. 

 Vreeland and I spent a portion of last summer in the southern 

 part of that State, and 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 differences were manifest 

 even early in the spring when the leaves unfolded. In 

 the Cuchara valley around La Veta scrub-oaks are very com- 

 mon. They usually grow in large 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 oaks also fruit very early, often be- 

 fore they are a meter high ; therefore, when a young oak has 

 started in a place, there soon grows up around it a whole 

 colony of still younger ones. As the youngest on the periphery 

 of the clump have more light and air, they grow faster and 

 soon overtake those in the center, and consequently the small 

 trees of the colony quite often have the same height (1-5 m.) 

 as if they were trimmed with a gardener's clipper. In rocky 



