368 Mr Witham o?i the Lepidodendron Harcouriii. 



detecting any traces of organization, that I cannot refrain from 

 mentioning the delight which I experienced when I observed a 

 structure so perfect. -ti . 



I am the more gratified, as it affords me an opportunity of 

 corroborating the opinion of so distinguished a fossil botanist as 

 Mr A. Brongniart, although founded solely upon the external 

 markings of the peculiar plants. 



To ascertain the correctness of his views, it became necessary 

 for me to examine into the internal structure of recent Lycopo- 

 diaceous plants, of which, however, I have only obtained speci- 

 mens of a single species. In so far as I have discovered, the 

 structure of this species is analogous, in most respects, to that 

 of the stem presented to me by Mr Phillips. 



The specimens of this plant which I have seen, consists of 

 subcylindrical or slightly compressed dichotomous stems. The 

 surface is covered by a thick envelope of carbonaceous matter, 

 presenting indistinct spiral protuberances, and beneath which 

 are observed numerous small papillae of an elliptical form, 

 higher than broad, and very regularly arranged in spiral series. 

 Fig. 1. Plate IV. represents a portion of one of the stems, with 

 some of the carbonaceous envelope remaining. 



Viewed in relation to its structure, the stem presents a cen- 

 tral axis, which may be seen in the transverse section, and in 

 the longitudinal section. Fig. 2. PI. IV., in the latter of which it 

 is entirely filled by calcareous spar, and a tube of carbona- 

 ceous matter. This axis consists of a central portion, which, in 

 the transverse section, presents rather an irregular cellular tex^ 

 ture, around which is a layer of cellular tissue, of large irregu- 

 lar polygonal cells, and lastly^ a layer with very small meshes. 



From the central column or axis, emanate on all sides cylin- 

 drical bodies, consisting of cellular tissue, with central fasciculi 

 of vessels* They proceed obliquely upwards and outwards, 

 and terminate in the papillary eminences of the surface of the 

 stem. They are seen cut obliquely, in the transverse section of 

 the stem, Fig. 3. PI. IV., where they constitute the white ob- 

 long markings dispersed in the brown parenchymatous sub- 



Stances. 



These processes, from the central axis or pith, are imbedded 

 in celluar tissue, constituting the great mass of the stem. In 



