204 VEGETABLE ORGANOGRAPHY. 



tudinal furrows. That which appegirs most singular in 

 its history is, that from time to time, (at periods which 

 I have not been able to determine, but I believe each 

 year,) three disks are "detached and thrown off from the 

 three round sides of the stem. These oval disks bear 

 upon their sides the remains of roots, which were the 

 most external of each of the bundles of adventitious roots. 

 I have not been able to discover any vessels in this 

 opaque, compact, and almost farinaceous mass of the 

 stem or stock of the Isoetes ; but I am inclined to believe 

 that they exist, since the leaves are furnished with 

 stomata. 



Art. II. — Of the Formation of the Branches 

 IN Endogenous Stems. 



From what we have seen in the preceding Article, it 

 is clear that the structure of Endogens appears less uni- 

 form than that of Exogens : and that which relates to 

 their ramifications, presents, in particular, much diver- 

 sity. The real number of these irregularities also seems 

 increased by this circumstance, that the number of woody 

 Endogens with which we are accurately acquainted is 

 very inconsiderable, and that we have very frequently 

 neglected the intermediate forms which might have been 

 able to give us an explanation. 



If in this as yet imperfect state of the science, we 

 endeavour to give an account of the ramifications of En- 

 dogens, we shall find great difiiculties. It appears to me 

 very likely that in the axil of each leaf there exists, as 

 in Exogens, a vital point, or latent bud ; and that this 

 rudiment can be developed, or not, according to circum- 

 stances. When the leaves are placed upon a knot, or 

 plexus of vessels, which arrests the progress of the sap, 



