74 FIRST STEPS IN GENERAL KNOWLEDGE. 



seeds, but they are differently formed. The seed 

 of an endogen, when it first begins to grow, sends 

 downwards a slender root called the radical, and 

 upwards a single seed-leaf or lobe, which is the 

 beginning of the young plant. But the exogens 

 do more than this, for they send up two seed-leaves 

 instead of one, as you may have often noticed in 

 lupines and other plants, where the two thick fleshy 

 seed-leaves push through the soil, nourishing and 

 protecting the young plant, and having a very 

 different appearance from the leaves which come 

 afterwards. Sometimes these seed-leaves remain 

 underground, as in the Windsor bean, and gradu- 

 ally die away when their purpose is answered. 

 Even before the seed has begun to sprout, these 

 differences are visible with the microscope ; but it 

 is not often necessary to examine the seed in this 

 way, because there is such a very plain and sim- 

 ple means of knowing endogens from exogens 

 without it." 



" You mean the straight-veined leaves and the 

 net- veined," said Henry. " Yes, that is a very nice 

 way of knowing them apart, and so little trouble : 

 I am getting quite a habit of holding up leaves to 

 the light to see which division they belong to. 



