THEORIES OF ORGANIC EVOLUTION 



now completely, now to a greater or less degree. Thus, 

 for example, the single flower is transformed into a 

 double one when, instead of stamens, petals are de- 

 veloped, which are either exactly like the other petals 

 of the corolla in form and color or else still bear visi- 

 ble signs of their origin. 



" When we observe that it is possible for a plant in 

 this way to take a step backward, we shall give so much 

 the more heed to the regular course of nature and learn 

 the laws of transformation according to which she 

 produces one part through another, and displays the 

 most varying forms through the modification of one 

 single organ. 



" Let us first direct our attention to the plant at the 

 moment when it develops out of the seed-kernel. The 

 first organs of its upward growth are known by the name 

 of cotyledons ; they have also been called seed-leaves. 



" They often appear shapeless, filled with new matter, 

 and are just as thick as they are broad. Their vessels 

 are unrecognizable and are hardly to be distinguished 

 from the mass of the whole; they bear almost no re- 

 semblance to a leaf, and we could easily be misled into 

 regarding them as special organs. Occasionally, how- 

 ever, they appear as real leaves, their vessels are capa- 

 ble of the most minute development, their similarity 

 to the following leaves does not permit us to take them 

 for special organs, but we recognize them instead to be 

 the first leaves of the stalk. 



" The cotyledons are mostly double, and there is an 

 observation to be made here which will appear still 

 more important as we proceed that is, that the leaves 

 of the first node are often paired, even when the follow- 



141 



