Jan., 1920] Resistance of Leaves to Transpiration 71 



loss. The ratios which are used in this series (series II) are the 



transpiration of mullein^ r xi j • j. • j ^i 



—. ; z „ . , for the same conditions and the 



transpiration of mullein- 

 transpiration of mullein^ - ^, J... /r^ • i J 



^. — -. ^ ,, . , for the same conditions. (Designated 



transpiration ot mullein"^ 



• 1 111 V-1 , V-1 , 



m the tables and curves as ^r^ and y^)- 



Series Il-b. The results of this sub-series, experiments 

 8, 9 and 10, are given on pages 79-80 and 68. In this 

 series mullein has the normal thick coat of hairs on its leaf 

 surfaces, mullein- has the hairs removed from the upper surfaces 

 of all the leaves, and mullein^ has the hairs removed from the 

 lower surfaces of all the leaves. The conditions under which 

 the experiments of this series are run are similar to those of 

 series Il-a, or in still air in the greenhouse. The results show 

 the daily march of transpiration, and the environmental 

 factors. The table of totals and ratios (Table V, page 85,) 

 shows that the removal of the hairs has not changed the ratios 



for the daily rates. TT2+h = 0.98, and ^3_^t^ = 0.82 in series Il-a, 



while in series Il-b these are 0.99 and 0.83. 



Series II-c. This sub-series of experiments was per- 

 formed under the same conditions as series Il-b, except that an 

 electric fan was used to produce wind at hour intervals. Experi- 

 ments 11, 12 and 13, on pages 81-82 and 70, are the 

 results of this sub-series. The wind produces considerable 

 increases in the evaporation rates, but there is no marked 

 differences in the transpiration rates of the three plants. In 

 Table VI, which gives the totals and ratios for this sub-series, 

 the totals for still air and wind intervals are shown, in addition 

 to the other totals. The total ratios for this sub-series are 



5J2=h = 0-91 and j^priH^O.iS 



Series Il-d. The same plants that were used in the first 

 three sub-series of this series were placed in the darkroom and a 

 record of the water loss obtained for three days. These results 

 are given as experiments 14, 15 and 16, on pages 82-83 and a 

 set of curves made for these experiments on page 72. 

 Table VII gives the totals and ratios for this sub-series: 



j^p^ = 0.56 and j^p=H = 0-65. 



