TYPICAL FORMS OF PLANT KINGDOM in 



it is formed by the growing together of the petioles of the leaves, 

 and there has been much discussion of this theory. Dicotyle- 

 donous plants are in a different case. Here the stem does not de- 

 velop from the leaf, but seems, on the contrary, to have produced 

 it. Hence the conclusion that the apparent formation of the trunk 

 from concrescent petioles was illusory. Perhaps it would have 

 been more logical to take as the starting-point the obvious 

 indications furnished by Ferns, and then to find out how the 

 initial method of trunk formation was able to give rise to a 

 structure characteristic of the trunk of Gymnosperms and 

 dicotyledonous Angiosperms. This indication provided by the 

 Ferns, Cycads, and Palms carries us further still. We have 

 only to examine the young branch of a Conifer to get on the 

 track of it. Without entering deeply into the problem we may 

 point out that the order of formation of the organs is often 

 altered by tachygenesis, and that where organs of independent 

 origin are fused into one, as more than one example will prove, 

 the new organ resulting from their fusion is formed, in the 

 course of embryogenetic development, before those parts that 

 have remained independent, thus appearing to be formed 

 at their expense. This is notably the case with the primitive 

 kidney or pronephros of Vertebrates. This observation gives 

 its value to Goethe's theory. He believed that every plant 

 is an association of leaves, and every leaf a kind of individual 

 which by its own indefinite repetitions forms the whole plant, 

 and by transforming itself gives rise to all the parts of the flower. 

 What Goethe divined from the study of flowering plants alone 

 has since then been demonstrated by the study of the vascular 

 Cryptogams. There the leaves, all alike at first and equally 

 capable of bearing sporangia, subsequently divide into two 

 types with distinct forms, the sterile leaves and the fertile 

 leaves. In the case of Club-mosses and Horse-tails, these leaves 

 form in groups around the end of the branches or stems and 

 hence presage the formation of the cones on the Conifers, which, 

 in their turn, shadow forth the flower. 



