374 Spalding: Absorption of atmospheric moisture 



Experiments of the same general character were conducted on 

 Prosopis, Parkinsonian Franseria, Atriphx, Encdia, and a number 

 of other perennials which represent the characteristic vegetation of 

 the region. To give these in detail would serve no useful pur- 

 pose, and the results may be briefly stated as follows : The mes- 

 quite (Prosopis) absorbs water vapor through its leaves, but at a 

 slow rate. Parkin so nia micro pliylla showed no capacity for 

 absorption of water vapor except as the specimens employed re- 

 tained their minute scale-leaves, and then only to a very limited 

 extent. Franscria deltoidea, Abutilon incannin and Encelia farinosa 

 all failed to show any gain whatever in a nearly saturated atmos- 

 phere until the experiments had been in progress from two to four 

 days. Later some absorption took place, but up to the time when 

 the leaves were plainly passing into a pathological condition the 

 amount absorbed was wholly inadequate to compensate for what had 

 previously been lost or even to restore turgescence. 



From the hygroscopic action exhibited by the fronds of Notlw- 

 laena sp., which in dry weather are rolled up, but are unfolded 

 after rain, it was thought that they would probably exhibit some 

 manifest capacity for absorption of atmospheric vapor, and this 

 anticipation was realized, although, as the records show, it would 

 take at least 14 days for the fronds under observation to absorb 

 from a saturated atmosphere what they had lost in twenty hours, 

 and keeping the curled-up fronds for days in a very moist atmos- 

 phere was not sufficient to induce their unfolding. Immersing in 

 water was soon followed by their expansion, and partial unfolding 

 was also induced by placing the subterranean parts in water. It 

 appears, then, that with the coming of rain the fronds of Notho- 

 laena absorb water directly and that this is also accomplished, 

 though with less prompt and complete unfolding, by the subter- 

 ranean parts. As the plant continues to absorb water from the * 

 soil the fronds remain expanded until the water supply diminishes 

 to a point where they begin to curl up. At this point a high per- 

 centage of atmospheric moisture would retard the process, thus 

 keeping them unfolded longer than if the relative humidity were 

 less, and maintaining them in an advantageous position for pho- 

 tosynthesis. 



A review of the data gathered establishes the fact that of the 



