THE STEM. 43 



the economy of Endogenous stems, of this variety particular- 

 ly, is lar from being riglitly understood. We liaxe made nia- 

 nv obsorvalions and experiments on tliem, and liave been led 

 to very ditferent conclusions tVom those universally advanced 

 by Botanists; but, l)et"ore we would advance opinions oppo- 

 sed to those of all writers of the highest distinction, we would 

 be sure that no error in observation, has led us to w rong con- 

 clusions ; and we make these remarks to direct attention as 

 far as we are able to the discovery of the true organization of 

 these stems, and the fimclions of the various organs of this 

 interesting class of vegetables. We shall content ourselves 

 at present with describirjg their structure, without atteuipting 

 to untold the peculiarities of their physiological organization. 

 If we take a part of the stem of the yucca and digest it in 

 diluted nitric acid it will be easy to discover the arranjiement 

 of its various parts. 'I'he zone composed of the basis of 

 the leaves will be found to consist o^l fibres proceeding from 

 the leaves and cclhdar tissue. These fibres i)ass down this 

 layer at ditferent distances, and then pass nearlv perpendicu- 

 larly through thf cellular and fibrous layers into the central 

 cylinder. It is usual to describe those diflerent layers as too 

 closely united to be separated, but we believe the only mean 

 bv which thev are united is the fibres liroceedinic throuirh them 

 from the base of the leaves ; for b) careful dissection after di- 

 gestion in diluted nitric acid we have, by merely severing these 

 fibres, obtained the layers perfectly separate, forming as even 

 a surface as those of the bark and stem of Exocens, and these 

 fibres may be traced from w illiin the leaf to the center of the 

 stem forming no more a part of the cellular and fibrous layers, 

 than the medullary processes form a part of the layers of 

 Exogenous sleuis. If we examine more closely the fibrous 

 layer, we sliall lind it to consist of materials arranged in all 

 respects like the liber of the bark. The fibres are interlaced 

 in a lateral direction only, as it may be divided into thin lay- 

 ers, but it cannot be torn in strips. The central rylindcr, as 

 we before reiuarked, consists of a large quantity of cellular 

 substance with the libres probably j)roceeding tVom the under 

 surf'ice of the leaves imbedded in it. These fibres consist of 

 spiral vessels in the c«'nter, and woody fibre siirroiinrling them. 

 They are arranged in no order. The central substance will 

 split in no direction, and in making a longitudinal section, it 

 must be cut or torn, as well as in making a transverse one. 

 From the manner in w Inch the new substance is deposited in 

 Endogens, it is impossible that the stems should increase in- 

 dilferently in diameter, although they are not so absolutely re- 

 stricted in this respect as Botanists generally pretend. Wo 



