78 The Great World's Farm 



moisture coming from the leaf-pores, as it escapes faster 

 than the air can evaporate it. This is the case with many- 

 grasses, especially the maize, which may be seen studded 

 with actual drops of water. 



A grass-plant gives up its own weight of water in the 

 course of twenty-four hours, in hot, dry weather; and a 

 square foot of turf will yield more than one and one-fifth 

 pints of water in this time. But a square foot of long 

 pasture-grass gives off nearly four and two-fifth pints, or 

 as much as one hundred and six tons of water to the acre! 



The larger the surface, the larger, of course, the amount 

 of water which passes off from it; and therefore the extent 

 of surface exposed is a matter of great importance, though 

 it is also one which we are very likely to overlook, at 

 least in many cases. Of course we can all see that a 

 tropical plantain, with its broad, large leaves, has a con- 

 siderable surface exposed to sun and air; and so with 

 other conspicuously large-leaved plants. But when, 

 instead of a few large leaves, a plant has many small 

 ones, it is not so easy to realize what the whole surface 

 may amount to. 



A sunflower, for instance, has leaves of a good size, 

 and yet it is rather surprising to find that in a plant only 

 three feet and a half high, the whole leaf-surface may 

 amount to more than thirty-two square feet! One speci- 

 men of this size was found to give up from a pint to a pint 

 and a half of water during a day of twelve hours. The 

 sunflower is quite outdone by the cabbage, however, one 

 specimen of which gave off nearly two pints and a half in 

 twenty-four hours, and that from leaves which, had they 

 been spread out, would have covered only nineteen square 

 feet. We have seen how well the cabbage is protected by 



