Pomona College Journal of Economic Botany 451 



thus enabling us to live up to our reputation of sparing no expense in the 

 beautification of our city. The care that many of our trees receive after this 

 manner of planting comes as a luxury to be enjoyed only on rare and mem- 

 orable occasions. However, there are so many opposing forces that combine 

 in their efforts to undermine the health of the street tree that it seems only fair 

 for us to apply our wisdom and knowledge to the best advantage of our 

 foliaged friends. For instance, most streets, especially where they have been 

 either excavated or filled, contain very poor soil, often clay or adobe, that 

 contains little plant food, besides being hard for the roots to penetrate; the 

 roots are generally deprived of sufficient moisture because of this hard soil 



^ Plate 195. Cocos palms. This palm makes a graceful and attractive plant for the short 

 or curving drive, but would seem monotonous if planted continuously on 

 a long avenue. 



and because the pavement keeps away much of the natural rainfall ; the soil 

 around the roots becoming packed, does not permit their proper aeration ; salt 

 water is often carelessly poured near the roots of trees in our city streets; 

 illuminating gas may seep through the soil, injuring the roots if not destroy- 

 ing the life of the plant ; injurious gases in the air, damage from overhead 

 wires or the gnawing of horses may all conspire to injure the tree. These 

 things work against the healthy, thrifty existence of these children of the 

 forest transplanted into an unnatural city environment, undermine their 

 health, threaten their very lives, so that we should bend our efforts to prevent 

 and overcome such detrimental influences. 



