372 TRANS. ST. LOUIS ACAD. SCIENCE. 



north of the great bend of the Colorado River, where Messrs. 

 Johnson and Parry have repeatedly examined numerous plants, 

 no fruit has ever been found. 



Page 54. T. Whipplei has now become quite familiar through 

 living specimens and beautiful photographs. From the latter we 

 learn that the scape is imbricately covered with conspicuous, 

 broad, at last patulous or drooping bracts, and that the panicle is 

 densely flowered, narrow, spike-like, almost lanceolate. 



About the Oaks of the United States. 

 By Dr. George Engelmann. 



We have quite a large number of oaks in the United States, 

 which for more than a hundred years have attracted the attention 

 of botanists, and we thought we knew them prettv well, i.e. we 

 thought we could distinguish, limit, and group the species. That 

 may have been so, to a great extent, in the old States ; but when 

 the Rocky Mountains came to be explored, and the regions west 

 of them, new forms were discovered, and often on single speci- 

 mens, and not rarely on imperfect ones, species were founded and 

 incompletely described, so that now a straight, clear path through 

 such intricacies is difficult to find. 



A striking example of the deceptive polymorphism of these 

 western oaks is furnished by the common Rocky Mountain scrub- 

 oak. This interesting species grows on the foot-hills of the east- 

 ern slope of the mountains of Colorado, sparingly near Denver, 

 scarcely north of that city, but abundantly southward, about the 

 Pike's Peak region, and thence extends through New Mexico 

 eastward into Texas and westward through Utah and Arizona 

 into Southern California. The centre of distribution perhaps, at 

 all events the classical locality of this species, are the mountains 

 above Canon City in Southern Colorado. 



In the valley and on the mountain slopes about this place the oak 

 thickets abound, 6-S ft. high, single trees occasionally 401-6 inches 

 thick and rising up to 12 or 15 feet, rarely higher. The leaves 

 are 3-4 inches long, broadly obovate, deeply lobed, sometimes 

 pinnatifid, underneath stellate-pubescent; the broad lobes obtuse 



