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classes were valid, the same experiments tried with leaves 

 of the third class would show an opposite result. This 

 is true in part, but the woody texture which is a marked 

 characteristic of nearly all the leaves of this class, pre- 

 vents the use of these simple methods, at least so far as 

 to render the results less satisfactory. 



The hair forming the filz of Populus alba L., Spiraea 

 ulmaria L., Rubus Idaeus L. and one variety of Vitis vini- 

 fera L. consists of a single epidermal cell prolonged to 

 a sufficient extent to form a thin filz, in all except Po- 

 pulus, where it is very thick. Here the epidermis cell 

 which forms the hair is smaller than the others, the hairs 

 very long, empty, walls thin and pressed together, matted 

 and twisted together into a filz several times thicker than 

 the leaf, stomata slightly raised. The leaf dipped in water 

 shows a silver color on the hair which soon disappears, 

 the surface soon becoming thoroughly wet. When sepa- 

 rated from the stem it grows brittle by losing water in- 

 stead of becoming limp as in case of the herbaceous 

 leaves. A leaf which was dry and brittle placed with the 

 under surface on the water for two hours, became fresh 

 and soft, but the upper surface was discolored being 

 nearly black. Others were picked from the stem and 

 while yet fresh were placed with their under surface in 

 contact with water. The next day they were still fresh, 

 the upper surface green and glossy. In similar ways efforts 

 were repeatedly made to compare the behavior of this 

 leaf in contact with water, with that of the leaves al- 

 ready described, but with no more satisfactory results 

 than the last mentioned. Unquestionably some moisture 

 was taken up by the surface resting on the water, for 

 the loss from evaporation from the upper surface and 



