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whitish filz, hair is thick walled so only a slight lumen 

 is seen, inclined to coil spirally, stomata raised, under sur- 

 face wets very slowly, its action in regard to absorbing 

 water very similar to that of Vitis. A slight quantity 

 is taken up but not enough to render it probable that 

 the filz plays an important part. 



In Spiraea ulmaria we find the same construction 

 with one exception. The walls of the hairs are thin but 

 not pressed together ; they are very small in diameter and 

 some appear to contain water or cell sap throughout 

 their entire length. The greater number, however, contain 

 air bubbles, or watery vapor. This air is seldom or never 

 of the same density as that of the outside atmosphere, 

 which is easily seen by adding water to the preparation 

 while under the microscope and watching the result. 

 The bubbles contract as the water enters the cell till 

 the air reaches the same density as that outside. Some- 

 times they disappear entirely, showing that instead of thin 

 air they consist of watery vapor. In these instances it is 

 not impossible that the hairs absorb water by the means 

 of atmospheric pressure as they do in the preparation. 

 It is extremely difficult to prove this by experiment, 

 but theoretically there can be no decided objections 

 against this supposition. However, it is not probable 

 that the amount of water thus obtained by the plant is 

 very considerable. 



Whatever the cause may be, the leaf actually does 

 take up water a little more readily than any of the three 

 others described. In none of these, however, is this action 

 decided enough to lead to the conclusion that this is an 

 important function of the filz. It may contribute slightly 

 to this result, simply by retaining and drawing the water 



