1914] Loughridge : Humus and Nitrogen in California Soil Columns 233 



and gives to the soil an adequate amount, especially in the upper 

 few feet. 



The Chino soil was found on previous examination to hold 

 quite high amounts of alkali salts, among which was nitrates of 

 soda and magnesia (Rept. Calif. Expt. Sta., 1894-5, p. 75). 



Mesa Lands. — The mesa lands that border the valley are 

 largely of a reddish loam type, interspersed on the north side 

 by deposits of sand and gravel from the hillsides. 



The red mesa extends eastward up the San Gorgonio Pass to 

 its summit at Banning, where it forms quite a high plateau above 

 Timoteo Caiion. 



A column of the sandy mesa of the north side was taken in 

 the western part of Highlands to a depth of twelve feet, in which 

 the sandy soil continued to the bottom. 



A column representing the red clay mesa was taken near 

 Redlands by Mr. F. E. Johnson. The upper five feet was of a 

 reddish sandy loam nature, below which it changes to a sandy 

 clay and finally to a gritty material. 



* Range of most annual plant roots. 



