18 REMARKS ON THE DISTINCTIVE CHARACTERS 



tion of a transverse slice of the stipe of Rhapis flabelliformis, extending 

 from the centre to the circumference. It exhibits a uniform parenchymatous 

 tissue, in which are interspersed bundles of elongated cells, presenting an oval 

 form in their transverse section, and in each of which are seen the apertures 

 of one or more large vessels. There is no pith properly so called, nor does 

 the bark differ materially in structure from the rest of the stem. 



Fig. 2. represents the Gymnospermous Phanerogamic stem, and is taken 

 from a portion of a transverse slice of a twig of P'mus balsamea, extending 

 from side to side. This figure exhibits, in the centre, the pith or medulla, 

 composed of large circular or subhexagonal cells, a ; two annual woody 

 layers or rings, b, b ; a portion of a third woody layer, c ; the bark, d; and 

 the epidermis, e. The dark lines proceeding like radii from the outer mar- 

 gin of the pith to the inner margin of the bark are the medullary rays. 

 The series of small cellules between these rays are formed by the apertures 

 of the elongated cells of the woody tissue ; and the irregular apertures in 

 the bark are those of the vasa propria, or vessels containing the resinous 

 secretions of the plant. 



Fig. 3. represents the Dicotyledonous Phanerogamic stem, being taken 

 from a portion of a transverse slice of a twig of the Common Ash, Fraxi- 

 nus excelsior, extending from side to side. It exhibits, in the centre, the 

 pith, a, composed of large circular or subhexagonal cells ; four annual woody 

 layers, b, b, b, b ; the bark in several layers, c ; and the epidermis, e. In 

 these circumstances it resembles Fig. 2, as well as in the medullary rays, 

 the reticular woody tissue, and the vasa propria ; but a remarkable diffe- 

 rence is presented by the irregular series of large oval apertures, placed in 

 the proximal portion of each woody layer. These are the mouths of the 

 spiral vessels. 



The appearances exhibited by the transverse sections of these three tribes 

 of plants are such, that the most careless observer could scarcely confound 

 them ; but as a botanical description of all the distinctive peculiarities of 

 their structure forms no part of my plan, I proceed to the detail of those 

 which more directly refer to the object in view ; and as the Gymnospermous 

 Phanerogamic plants, or Conifers, are those to which our observation is to 



