fl> o s t e I 3 ia 



individual species as Andropogon halii 

 and Sitanion brevifolium. Probably the 

 most striking plants of midsummer are 

 Cleome and Euphorbia marginata. Of the 

 plants of less conspicuous appearance 

 Solajitim rostratum and other species of 

 Solatium, Salvia lanceolata, Ckenopodium 

 ambrosioides and the everywhere abun- 

 dant sage bush (Artemisia spp.), make 

 up a considerable portion of the ruderal 

 flora. The zonal distribution of road- 

 side plants is well illustrated in many 

 places, especially where there is an 

 irrigating ditch at the side of the road. 

 This serves to keep some considerable 

 space moist while the other parts of 

 the road are very dry. The distance 

 through which the water of the ditch 

 seeps varies with the character of the 

 soil but there can almost always be 

 recognized an intermediate zone between 

 the wet and dry places. Plants which 



