THE VEGETABLE KINGDOM. 



361 



velope, or calyx, is formed by the first whorl of metamor- 

 phosed leaves, and as the transformation of these is much 

 less radical than in the other parts, the different parts of 

 this organ, or the sepals, in many cases remind us of the 

 leaves by their structure and coloring. The internal en- 

 velope, or corolla, although more brilliant than the other, is 

 nevertheless also formed by a whorl of leaves, the second. 

 Each of these leaves is called a petal. The stamens, which 

 represent the male apparatus of plants, result from the 

 metamorphosis of the third whorl of leaves ; these depart 

 so far from their normal type that analogy alone shows 



168. Stamen of the 

 Potato. 



169. Four-Celled Anther of 

 the Persian Laurel. 



170. Stamen of the 

 Amaryllis. 



what their fundamental structure really is. Finally, the pis- 

 tils, real organs of maternity, are derived from the fourth, 

 or innermost foliaceous ring. 



Simple analogy made the naturalists of antiquity suppose 

 that plants, like animals, present two sexes, but they had 

 only very confused ideas about them. 



It was only in the seventeenth century that Camerarius, 

 a physician of Tubingen, hit upon the real truth, which he 

 expounded in a letter that has become very celebrated. 



