PLATE 4 
A. —Creosote bush association. A pure stand of Covillea glutinosa (Engelm.) 
Rydb. The wide spaces between the plants are well covered with an ephemeral 
growth of Plantago erecta Morris. This condition is found only following a 
period of rainy weather, and the annual vegetation entirely disappears during 
the long drought periods. (See PL 3, B.) Chandler, Ariz., March 15, 1915. 
B. —A plant of CoviUea glutinosa (Engelm.) Rydb. showing the loose open 
branching of the top and the spreading habit of the root system which is well 
adapted to utilize the soil moisture of the wide spaces between the plants. Indio, 
Calif., March 7, 1915. 
