- 16 — 



water remains in the hair meshes and how much has 

 actually entered the leaf tissue at the time of weighing. 

 The method used proves beyond a question that some 

 of the water applied must have entered the tissues, as 

 by no other means could the leaf have resumed its 

 turgescence. 



The question remains to be answered, what part 

 was played by the hairs in this process. To answer 

 this another example may be given, namely, Salvia ar- 

 gentea L. The lower or root leaves of this plant are 

 large and thickly coated on both sides with long, soft, 

 white hairs which remain during the entire season. Above 

 on the stem the leaves are gradually smaller and less 

 filzig, the surface of the extreme upper ones being barely 

 covered. The anatomy of the filz differs but little in 

 principle from that of Helichrysum petiolatum. The living 

 cells, however, are much larger, averaging 35 mik. 

 in diameter, in length the shorter ones are 100 mik., the 

 longer from 400 to 500 mik. There are usually more 

 of these in number than in the Helichrysum hair. The 

 end cell is always thin-walled, remaining small from the 

 first, as may be seen in some instances where the con- 

 tents are not lost, about 15 mik. in diameter, and so 

 long as to make it impossible to extricate any from the 

 filz to measure them, flat, pressed together, sometimes 

 divided in two by a partition wall, makes rather a loose 

 filz; stomata, raised somewhat not so much as in many 

 other instances. 



It is not difficult to calculate approximately the 

 amount of surface thus gained over the ordinary epider- 

 mal surface. In addition to this, the leaf blade, which 

 is about 10 by 12 centimeters in size, is so constructed 



