122 The Great World's Farm 



however, and why plants cannot help themselves to it — 

 when they can, and do, take up carbon dioxide from the 

 same source — one cannot say; but such is the fact. Both 

 are gases; and as nearly four-fifths of the air consists of 

 nitrogen, there is certainly no lack of it. However, the 

 plant takes the one up by its leaves, as will be seen in the 

 following chapter, and does not take the other, much as 

 it wants it. 



All animal and vegetable matter, then, contains nitro- 

 gen; and as all plants, whether lichens and mosses, or 

 oaks and palms, must have some amount of it, they most 

 of them get it from this source — the decayed organic 

 matter in the soil. 



But there are others which get it equally well from 

 living matter. The mistletoe and other similar plants get 

 this, as well as other food, from the living trees or plants 

 upon which they grow. And other plants, again, some- 

 times turn the tables on the animal world, and actually 

 devour living insects. 



The plant called Venus's fly-trap is one of these insect- 

 eaters, and a very curious plant it is. Its leaves end in 

 two lobes, on each of which are three delicate hairs, so 

 placed as to form a triangle, and in such a position that it 

 is almost impossible for any insect alighting upon the leaf 

 to help touching them. As long as the leaf only is 

 touched, no harm is done, but if but the tip of one of 

 these magic hairs be touched, the leaf closes instantly 

 upon the victim, and does not reopen until it has sucked 

 it dry. The trap will close equally upon a dead, dry fly, 

 or any other substance placed upon it, but it reopens 

 almost immediately, when the plant, by some mysterious 

 instinct, discovers that the morsel is indigestible. 



