126 PHYSIOGNOMY OF PLANTS. 



tion of fluids, is dependent on the pressure of the atmos- 

 phere. Therefore it is that alpine plants are more aromatic, 

 and are hairy and covered with numerous pores. (See my 

 work tiber die gereizte Muskel-und Nervenfaser, Bd. ii. 

 S. 142-145.) For according to Zoonomic experience, organs 

 become more abundant and more perfect in proportion to 

 the facility with which the conditions necessary for the 

 exercise of their functions are fulfilled, as I have elsewhere 

 shown. ,In alpine plants the disturbance of their skin- 

 respiration occasioned by increased atmospheric pressure 

 makes it very difficult for such plants to flourish in the low 

 grounds. 



The question whether the mean pressure of the aerial 

 ocean which surrounds our globe has always been the same 

 is quite undecided : we do not even know accurately 

 whether the mean height of the barometer has continued 

 the same at the same place for a century past. According 

 to Polenfs and Toaldo's observations, the pressure would 

 have seemed to vary. The correctness of these observations 

 has long been doubted, but the recent researches of Carlini 

 render it almost probable that the mean height of the baro- 

 meter is diminishing in Milan. Perhaps the phenomenon is 

 a very local one, and dependent on variations in descending 

 atmospheric currents. 



(is) p . 20." Palms." 



It is remarkable that of this majestic form of plants, 

 (some of which rise to more than twice the height of 

 the Royal Palace at Berlin, and to which the Indian 



