The Growth of Seeds 33 



into all the crevices in the earth, and so thin skinned 

 that the water can easily pass into them. They stick to 

 particles of soil and draw from them all the moisture 

 that is wanted. These hairs only live a few days, then 

 they die down and others spring up nearer the tip to 

 take their place. This process always goes on, even in 

 an old tree, for the tree must have water, and it is only 

 through the root hairs that it can obtain it. 



After your bean has been growing for about another 

 week its skin will begin to split. Then the stalk joining 

 root and shoot grows longer and finally pulls the shoot 

 out. This shoot has exactly opposite properties to the 

 root. It grows towards the light and directly away 

 from the earth, so that, in whatever position you place 

 it, it grows straight up, just as the root grows straight 

 down. This property is very important to heavy trees, 

 for if it did not exist they might grow crooked, and 

 then their boughs and leaves would weigh them down 

 and they would fall by their own weight, just as a 

 crooked pillar would. 



When the shoot has come out, the split outer skin 

 gradually comes off and the two cotyledons separate. 

 In the bean and acorn they remain underground and, 

 having fed the young plant as long as it needed it, rot 

 away. In many trees, however, they come to the top of 

 the ground with the shoot, and, becoming green, appear 

 as the first two leaves. This is what happens in the 

 sycamore and in all other young plants whose first two 

 leaves are quite a different shape from any of the later 

 ones. Two is not the only number of cotyledons a 

 seedling can have. It may have five to ten, like the 

 pines, or it may have only one. Plants are called 

 poly-cotyledons, di-cotyledons, or mono-cotyledons 



G. 3 



