proceedings: botanical society 501 



lowland tropics. Mangrove formations line the sea coast and extend 

 up the rivers 30 miles or more. In the main the country is covered 

 with forest, but the Venezuelan savannas extend across the southern 

 part of the Colony. 



Prof. Hitchcock collected all kinds of flowering plants, though special 

 attention was given to the grasses. About 1 100 numbers were obtained, 

 including 108 sets of grasses. The trip was made under the auspices 

 of the U. S. Department of Agriculture, the New York Botanical 

 Garden, and the Gray Herbarium. 



144TH MEETING 



The 144th regular meeting of the Botanical Society of Washington 

 was held at the Cosmos Club, 8 p.m.. May 4, 1920. Thirty-two mem- 

 bers and four guests were present. 



Under "Brief Notes and Reviews of Literature," Dr. C. D. Marsh 

 discussed the peculiar appearance of defoliated aspens which he had 

 observed in the Wasatch Mountains. The trees had put out their 

 foliage on certain branches, only producing dense clusters of very 

 large leaves, which gave a "witches-broom" effect. 



An illustrated paper on The phytogeography of the Coeur d'Alene basin 

 of northern Idaho was read by Dr. H. B. Humphrey. He explained 

 that in pre-miocene times that fork of the Columbia River draining the 

 western slopes of the Bitter Root Mountains flowed northward through 

 the Purcell trench. Eruptions of lava which crept up the valley ob- 

 structed the flow of the river, but through long-time erosion the stream 

 reopened its channel and was probably active until the recent ice age. 

 The retreating glaciers of the ice age left a dam of pleistocene gravel 

 in the valley at the head of the present Coeur d'Alene Lake. The 

 average elevation of this gravel dam is 2,155 ^^et above sea level. 

 This deposit of gravel caused the Coeur d'Alene basin to fill and form 

 a lake of great extent. 



Ancient markings indicate that the surface elevation of this lake was 

 approximately 2,135 f^^t above sea level, or approximately 20 feet 

 lower than the crest of the gravel dam. This lake subsequently found 

 an outlet through the present Spokane River. 



Excessive deposition of silt brought down from the mountains resulted 

 in the development of river banks throughout the length of the east 

 and southeast arms of the lake. The seasonal inundations have grad- 

 ually raised the floor of the basin. Aided by the accumulation of 

 vegetable detritus, tievelopment of meadows followed. The filling-in 

 process has progressed slowly, leaving at the upper reaches of the old 

 lake arms a flood plain of highland meadows and typical mesophytic 

 vegetation, which tapers off into lowland meadows and marshes fol- 

 lowed by common hydrophytes such as Sparganium, Acorus calamus, 

 Equisetum fluviatile, Sagittaria, etc., and finally by such plants as 

 Potamogeton, Utricularia, Nymphaea, etc. 



