FOEMS OF LEAVES 3 



No one who has ever looked at seedlings can fail to have 

 been struck by the contrast which the cotyledons afford, not 

 only to the final leaves, but even to those by which they are 

 immediately followed. 



Let us then take certain plants (especially, as far as 

 possible, the commonest and most familiar), and see what 

 light can be thrown on the varied forms which their seedlings 

 present. Look, for instance, at the familiar Mustard and 

 Cress ; the first (fig. 3) has kidney-shaped cotyledons, one of 



PIG. 3. Seedling of Mustard 

 (Brassica nigra), x 8. 



FIG. 4. Seedling of Cress 

 (Lepidium sativum), x 3. 



them rather larger than the other : while the Cress (Lepidium 

 sativum) (fig. 4), on the other hand, has the cotyledons divided 

 into three lobes. The Pink (Dianthus) (fig. 22) has broad 

 cotyledons, the Chickweed (Cerastium) (fig. 23) narrow ones ; 

 those of the Beech (fig. 13) are fan-shaped in outline ; those 

 of the Sycamore (fig. 9) shaped almost like a knife-blade ; those 

 of Eschscholtzia (fig. 40) divided like a hay-fork ; those of 

 the Bean or Acorn thick and fleshy. 



Mustard and Cress were the delight and wonder of our 

 childhood ; but at that time it never occurred, to me at least, 



