TRANSPIRATION OF WHITE PINE SEEDLINGS 5 



No shade 2 . 18 



Half shade 2.70 



Full shade 6.89 



These figures show that there was a difference in the material 

 taken from the soil by the three plants. 



Returning to the figures given for transpiration, it is seen 

 that the plants which transpired the most water, the plants in 

 no-shade beds, contained the smallest per cent of ash and that 

 the plants which transpired only one-twentieth as much water 

 contained the largest percentage of ash. Again taking the total 

 amount of ash absorbed, it is seen that there is no very evident 

 relationship between the amount of water absorbed and the 

 amount of ash taken up, twenty times the water is accompanied 

 by only five times the ash; eight times the water by three times 

 the ash. The plants then are able not only to select the minerals 

 which they take from the soil but also to control the degree of 

 concentration of the solution which enters the root hairs. 



Pfeffer in describing the experiment of Schlosing, who found 

 that tobacco plants grown under bell jars did not grow as well 

 as others, says — "Though a variety of other factors enter into 

 play here, such experiments suffice to show that transpiration 

 favors the absorption of the constituents of the ash." This 

 statement should be closely questioned — when applied to our 

 pine seedlings. Oven has shown that even a clear glass cover 

 greatly increases the nitrogen content and from the fact that the 

 plants in full-shade and half-shade beds already have a surplus 

 of ash over the no-shade or normal plants, it seems highly prob- 

 able that some of the other factors may be more important in 

 determining the amount of ash absorbed. The lack of growth of 

 seedlings in full-shade cannot be due to lack of water or the 

 .amount of ash. Lubiminko remarks that pea pods grown in 

 the dark seem to have a higher percentage of ash. He asso- 

 ciates the percentage of ash with light rather than transpiration. 

 According to the work of Pagnoul and Oven, the nitrogen con- 

 tent of sugar beets and potatoes increase as much as ten times 

 when plants are grown in the shade. Oven associates this with 



