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Pub. Puget Sound Biol. Sta. Vol. 2, No. 47 



PLATE 36 



A drying' rack used in the work rooms at the University of Washington. A 

 working drawing is' shown in plate 43, Fig 1. 



difficult steps in the preparation of the moss for dressings and one that 

 has required a great deal of careful thought and experimentation. This 

 is particularly true along the Pacific Coast during the wet season when 

 the atmosphere approaches saturation for months at a time. 



Experiments have shown that artificially dried sphagnum is harsher 

 and far more brittle than moss that is dried in the open air under or- 

 dinary conditions. This is due to excessive drying in which not only the 

 water contained in the reservoir cells is removed but also that in the 

 green cells and the walls of the plant. It is the removal of this excessive 

 amount of moisture, depriving the plant of its elasticity, that makes it 

 brittle and harsh. In ordinary air-dried moss a portion of this moisture is 

 retained by the plant for a longer time, and if removed at all it is so 

 gradually that the walls are left flexible. Dr. Porter suggests that "it 

 is probable that the controlling factor is the relative humidity of the cir- 

 culating air rather than the rate at which the sphagnum is dried. For 

 example, I see no difference between moss dried in summer by placing it 



