SUB-IRRIGATION FOR LETTUCE. 73 
houses where the moisture in the air, in addition to the 
normal quantity, comes almost wholly from plant tran- 
Spiration. 
‘‘In the following table, the results with a number of 
varieties are given. This was not intended as a variety 
experiment, as those in the list are not comparable in the 
manner presented, since some are varieties which form 
heads while others do not. All that it is intended to 
show is the relative development of each variety by the 
two methods of watering. In this experiment each lot is 
carried through the entire season of growth by the method 
indicated. That is, the sub-irrigated plants were treated 
in that manner from the time the seed was sown until 
the crop was harvested. The surface-watered plants, on 
the other hand, were surface-watered during their entire 
season of growth. This is referred to particularly be- 
cause it is not the plan which has been followed in the 
greater number of our experiments. It will be seen that 
the average gain in favor of the sub-irrigated plots was 
about roo per cent.— 
THE RESULTS OF SURFACE- AND SUB-IRRIGATION WITH 
TEN VARIETIES OF LETTUCE. 
Surface-watered. Sub-irrigated. 
Variety. 
Number of | Weight, | Numberof | Weight, 
plants. ounces. plants. ounces. 
Chicago Forcing ... 5 II 5 22 
Denver Market... 5 8 5 12 
Tilton’s White Star. 5 II 5 32 
Henderson’s N.Y. . . 10 22 $e) 40 
ET ANSON 56. sie) ca: Io 18 Io 48 
Grand Rapids .... 25 | 80 | 25 208 
Teebere ise ss 15 32 15 47 
Bice BOstONes . 2 as 15 21 15 51 
iarge Boston ...: .. 10 14 10 31 
Rawson’s Hot-House . 15 23 | 15 4I 
‘In the next table, the separate results of 15 ex- 
