276 THE PLANT WORLD. 



constant throughout the entire experiment. The weight of 

 evidence, both from this experiment and from a number of 

 observ^ations on the behavior of the native desert plants, is 

 decidedly in favor of the conclusion that the evaporating 

 power of the air is an important factor in controlling desert 

 vegetation, aside from its indirect influence through the con- 

 ditions of soil moisture. 



Desert Laboratory, Tucson, Ariz. 



WILD FLOWERS OF THE "TIP-TOP BOTTOM." 



By Felix J. Koch. 



There is one excursion out from San Diego, (Calif.), 

 down to the tip-top bottom of the country, where the United 

 States, Mexico and the Pacific meet, that is made by compar- 

 atively few persons. This is owing, first, to the expense of 

 hiring one's own vehicle; to the time, in that it takes an en- 

 tire day, and, finally, to the fact that a permit must first be 

 secured from the Mexican alcalde at Tia-Juana, for only 

 the smuggler or the border jumper Is supposed to have real 

 occasion for going here. As a matter of fact, however, this 

 corner of the southwest affords an exhibition of the flora 

 of that section that Is unexcelled. 



Leaving San Diego early on a February morning, 

 blooming almond trees and trumpet vines grace the several 

 gardens. Then, where one passes out of that city Into Na- 

 tional City, a suburb to all intents and purposes, tall euca- 

 lyptus, or "blue gums," flank the way, these with their deep 

 green, wlllow-lIke leaves occasionally interspersed with leaves 

 of actual blue, or else a grape-like bunch of seeds. Here, 

 too, every home has its garden, and now and then there Is an 

 olive grov^e. Yellow daisies and prickly pears grow at the 

 road-side and here and there a pepper tree, laden with scarlet 

 berries, throws Its shade. 



