Green Leaves at Work 113 
its habitat. The slender blades and delicate 
fringes are adapted, like fishes’ gills, to bring the 
greatest possible area of surface into contact with 
the water, and thus, also, with the air, which is 
diffused through it. 
And the waves and currents, which might tear 
a broad leaf to ribbons, glide harmlessly through 
these blades and fringes, just as the ocean gales, 
which rip the Canna leaves in our summer cottage- 
gardens into ‘‘smithereens,” sough harmlessly 
through the slender needles of the coast pines. 
The thick, fat foliage of the house-leek, the 
aloe, and the century-plant does double duty. 
These leaves not only prepare nourishment for the 
plant, but also serve as storehouses to hold it. 
Their whole interior is white as that of a potato, 
and, like that useful vegetable, they are heavily 
loaded with starch, while their green surfaces fulfil 
the ordinary use of foliage—transpiration and di- 
gestion. 
As an Irishman might put the case, there are 
leaves which are not leaves at all—but are some- 
thing else. 
At the end of a climbing spray of the pea or 
vetch the topmost leaf—or a part of it—becomes 
(Fig. 23) a tendril by means of which the vine clings 
