THE VEGETABLE KINGDOM. 229 



touching the bark, surrounding a central pith and having 

 wide medullary plates between them ; in fact, when the stems 

 of this plant are in a state of decay, the eight fibrovascular 

 wedges may be pulled asunder, like those of a Menisperma- 

 ceous plant. In Testudinaria elephantipes the structure of the 

 stem is of nearly the same kind ; several bundles of fibro- 

 vascular tissue form a circle surrounding a pith, and pierced 

 with broad medullary processes. Lapageria and Philesia have 

 each a zone of wood below their bark, and a central pith 

 in which the common fibrovascular bundles of Endogens are 

 disposed ; a tendency to which is also observable in Smilax. 



8. It seems therefore clear that what I have elsewhere 

 called the Retose group is composed of plants whose mode of 

 growth is essentially different from that of Endogens in general ; 

 and that the species composing it stand in the same relation to 

 the mass of Endogens, as Homogens to the mass of Exogens. 

 For these reasons it appears that Endogens contain three dis- 

 tinct types of organization, namely, Spermogens and Sporogens, 

 or Rhizanths, the former of which consists 1 . of true Endogens 

 with striated inarticulated leaves, and 2. of false Endogens with 

 reticulated disarticulating leaves, or Dictyogens. 



9. From these considerations we learn that of the three 

 primary divisions of the Vegetable Kingdom, recognized by 

 Jussieu, two require to be broken up into three each, and the 

 other into two ; making eight in all ; the mutual relations 

 of which with each other and the Animal Kingdom may be 

 expressed thus : 



Exogens. 



Homogens. Dictyogens. 



Gymnogens. Endogens. 



Cormogens. Sporogens. 



Thallogens. 







(Animal Acrita Kingdom.) 



The following analytical arrangement will bring these dis- 

 tinctions more plainly into view. 



