THE LEAVES 59 



earth.* Indeed, as we have seen, there are plants, 

 like the forest orchids of Queensland, that do not 

 touch the earth at all, but get all their food from air 

 and moisture. Look also at the elk-horn fern which 

 you see so often growing on the walls of houses. 



3. The solid food got by the root, though not great 

 in amount, is important ; and the plant cannot live 

 without it. All plants need the same air-food, but 

 they differ greatly in the kind of root-food they need. 

 Soils, too, differ greatly in the kind of root-food they 

 can give, and this is why we find some kinds of weeds 

 or trees plentiful in clay land, and other kinds in light 

 soil : one kind in rich, deep soil, and another kind in 

 poor soil. Fix firmly in your mind, however, the fact 

 that the plant is built up mostly from food got from 

 air and water. 



4. The wonder of it all. Think of the largest gum 

 tree you know. How wonderful that it should be 

 built up out of something that you cannot see : the 

 invisible made visible! What wonder-workers the 

 little leaves are that glance in the sun and flutter in 

 the breeze ! How hard they must work to build up 

 those mighty towers of branch and leaf ! 



5. How the plant turns dead stuflFs into living 

 foods. And did you ever think how strange it is that 

 the leaf is able to feed on dead things that you could 

 not live on. All the food you eat was once alive ; but 

 the plants can eat carbon and lime and other things 



* Behind Professor Nobbe's Forest School in Saxony there are trees that 

 have been grown in huge glass jars of water. Into this water once a month 

 are placed measured amounts of nitrogen, and the other root-food, Though 

 the roots have never been in touch with earth, the trees have thriven for 

 over a quarter of a century. Experiments of a similar kind are said to 

 have shown that out of every 100 lb. of wheat harvested, only 1 lb. is from, 

 the soil. The rest is from air and water. 



