PROBLEMS OF THIi DKSKRT. 37 



cactus and certain animals, with the water supply as the 

 indirect crucial factor. 



In addition to questions toward which the desert offers 

 the main and nearly sole opportunity for solution, there are 

 problems which require a consideration of the entire range 

 of climatal conditions for their complete understanding. An 

 illustration of this is to be found in the functional action of 

 stomata. 



Scores of contributions have been written from studies 

 upon stomata made in humid, tropical and temperate cli- 

 mates upon the finely automatic action of these organs in 

 regulatory response to transpiration conditions. The re- 

 searches at the Desert Laboratory, especially those by Lloyd, 

 show that stomata open, widen and close in response to 

 other stimuli than those arising from the humidity or aridity 

 of the air and the turgidity or flaccidity of the leaf, making 

 necessary and possible a new version of the physiology of 

 foliar organs. A similar case is presented by the relations of 

 the plant to soil-moisture. 



It needs but a moment's consideration to show that our 



pschycological attitude toward such matters is faulty. The 

 features of plant life of the moist, temperate and tropical 



climates are subconsciously assumed to be normal, typical or 



average, while forms native to other regions are regarded as 



adaptational and abnormal. 



In a broader view however, clothing of stems in wax, 

 hairs or spines are no more adaptations than bark, leaf-ex- 

 cision and scores of other devices. Without doubt had these 

 structures been first described by the botanists of a desert- 

 dwelling people much would have been made of them as 

 adaptive non-typical formations. The activities of the stu- 

 dent of desert forms will indubitably contribute to a rear- 

 rangement of perspective upon many phases of morphology 

 and physiology. 



The attack of problems under untried conditions implies 

 efficient weapons, new methods of attack and so far as the 



