56 STUDIES IN THE VEGETATION OF THE STATE 



The lact that after being revived the plants could not 

 reduce the physiological water to as low a limit as before 

 indicates that the absorptive system of the plant had 

 suffered serious injury before they were revived. It must 

 be that the root-nairs and even the finer roots had been killed. 

 If this be the case in nature, a temporary shower could not 

 furnish the plant with sufficient water to grow new root- 

 hairs, and the plant would continue to die in spite of the 

 slight addition to the soil moisture. 



' ' From the results it might bo inferred also that in times of 

 drought a shower might be of absolute harm. In some local- 

 ities in the West many farmers believe that in times of 

 drought a small shower not sufficient to "wet down the soil" 

 is an injury to the crop. But this can hardly be true since 

 the shower checks the rapid loss of water from the plant by 

 evaporation and enables it to live longer and may be the 

 cause of prolonging its life until heavier rains fall. 



8. TJie Limit of Physiological Water ; Variations in Different 

 Oenera and Species. 



The notes from experimentation indicate in a general way 

 variations in the limit of physiological water corresponding 

 to the natural habitat of the plant. The limit for meso- 

 phytes for loamy soils falls generally between 5 to 11 per 

 cent. 



Mesophytes with xerophytic tendencies may drop below 

 this general average in their limit while, those bordering 

 on hydrophytes in their habitat may have a limit even 

 higher than this. By arranging the limits in a descending 

 series commencing with amphibious plants, or those that 

 root in mud, and passing through the mesophytes to 

 xerophytes, the amount of non -available soil water in loam 

 decreases from 20 per cent for some amphibious plants to an 

 air dry soil as a limit for intense xerophytes. 



Fleshy plants have lower limits than woody ones. Nas- 

 turtium and Coleus, although not true succulents, retain 

 water so tenaciously in their stems that the soil becomes 

 almost air dry before they die. 



