108 



soft tender plant, while in the Bahamas what is apparently the 

 same species grows in dry pot-holes and is firmer and stronger. 



The second paper was by Dr. D. T. MacDougal on " Desert 

 and Delta Vegetation of Sonora and Baja California." . The 

 Colorado river has been called the Nile of America. It flows 

 600 miles without tributaries and has a delta i 50 to 200 miles 

 long by 50 to 100 miles broad. In this region is the most pro- 

 nounced desert in the United States and probably in America. 

 The topography of the region ma}' be described as a great basin 

 with the Colorado River flowing along the eastern margin. The 

 Salton basin is 400 feet below sea level and in times of unusual 

 flood is transformed into a great lake by overflow of the Colorado 

 river, the last such flood occurring in 1891 when part of the 

 track of the Southern Pacific Railroad was under water. At one 

 point in this basin there has been an elevation of mud volcanoes 

 from 10 to 50 feet high, where there are hot sulphur springs. 

 The dry season is from August to April or May. At the end 

 of the wet season the Indians dig holes deep enough to get into 

 and plant their corn and melons in these. The surface of the 

 ground becomes very dry but enough moisture is retained to 

 mature the crops. Within a few yards of the river-channels re- 

 lative humidities of 11, 12 or 13 per cent, were observed. The 

 temperature of the summer flood water is 45° to 55° while the 

 air temperatures are the highest to be found in the country, 100° 

 to 125°. At the lower end of the delta is a region of brackish 

 water. 



Distichlis spicata is widely distributed on the mud flats ; the 

 Mexican poplar, an unidentified willow, and the mesquite were 

 the trees observed, while the arrow-weed forms almost impene- 

 trable thickets. Within the widtli of a few yards one passes from 

 river vegetation to true desert. 



Annnobroina Sonorae, described by Torrcy, has a stem 2 to 4 

 feet long, all buried except the head. It is parasitic on Atriplex 

 roots. A puff ball with the same form and similar appearance 

 was found, but it was too brittle to stand carrying. 



The east coast of Baja California, near the head of the Gulf, is 

 suppo.sed to be the driest spot in America. One half inch of rain 



