436 BOTANICAL GAZETTE. . [JUNE 
6. All coverings became more efficient in the wind (column 7 
in all series). 
7. The efficiency of hairy coverings, in thicknesses at all approach- 
ing those actually found on leaves, was very slight in still air (series I, 
II, and III, column 3, line 2, etc.). 
8. Such coverings became very efficient in wind (same series, 
columns 6 and 7). 
g. Their efficiency increased in wind much more rapidly than 
did that of wax (same series, column 8). 
10. Even the layer of cotton 2°™ thick did not eal the layer of wax 
as a protective device. In still air the difference between the two 
was marked, but in wind became less evident. 
11. The thinner coverings showed a greater increase in efficiency 
over wax than did the thicker (cf. column 8 in series I, II, II, IV, 
and V). 
12. Such thin coverings as strigose hairs and mosquito netting 
produced scarcely any effect in still air, but showed a marked effi- 
ciency in the wind, the increase being 4—20 times, which was 2.9-12 8 
times that of wax respectively (series IV and V, columns 7 and 8). 
Both of these materials may retard in wind as much as 5.6 to 17-4 
per cent (series IV and V, column 6). 
13. The effect of sunshine was marked. In still air the thin 
and thick hairy covering became 1.5~-1.6 times more efficient when 
compared with wax. In the wind in sunshine the increase in effi- 
ciency was not the sum of the increase due to wind in shade and to 
sunlight in still air, as one might at first expect, but represented an 
increase in efficiency over still air in shade that was even somewhat 
less than the increase in wind shade over still air shade (series H, 
column 3, series IIA, column 6, and series II, column 7). 
14. If hairy coverings on leaves behave in the same way aS out 
artificial hairy coverings, we may say that they produce compara- 
tively little effect in retarding transpiration in still air, but have @ 
marked protective action in wind. Thin strigose coverings pe 
no appreciable effect in still air, but become important factors } 
wind. A waxy (i.e., cutinized) covering is more efficient, and has 4 
more constant retarding effect at all times. In sunshine hairy 
coverings are increasingly protective, their increase in efficiency being 
