The Primary Structure of the Stem of Catamites. 163 



ising process. On the inner, and more especially on the 

 outer, side of these larger and more central elements, which 

 are practically continuous all round the stem, are smaller 

 elements of a different character, n. In transverse section, 

 they have a more circular outline, and there are distinct 

 evidences of thickening deposits having been laid down upon 

 the original walls. On the outer side of the zone under 

 description they form two or three layers, and at some 

 points they are found penetrating in triangular masses 

 between the larger elements of the middle. On the inner 

 side they chiefly fill up the angles between the larger middle 

 elements, so that the entire zone has a tolerably uniform 

 width, with more or less even and uniform margins. 



The outer zone of the cortex, 0, is seldom well preserved, 

 but it appears to have been composed of a thin-walled 

 tissue, in which thicker-walled elements were imbedded. 

 The latter have very thick walls, with clear rounded lumina, 

 and are somewhat irregularly distributed. A curious point 

 is, that they vary much in size. 



At the periphery of the section is the epidermis, but in 

 this, as in most specimens, its structure is for the most part 

 obliterated. At a few isolated points, however, we can 

 make out that it originally consisted of a single layer 

 of cells. 



My efforts to obtain longitudinal sections of this type 

 of stem in its primary condition have not yet been as suc- 

 cessful as could be desired. Numerous fragments have 

 been met with, but no one large and complete enough to 

 give a connected view of the primary tissues in their longi- 

 tudinal aspect. Nevertheless, by putting together the items 

 of information picked up from a large number of these 

 fragments, we may obtain a fairly reliable idea of the 

 longitudinal structure, at least in its main outlines. The 

 following description is based upon knowledge obtained in 

 this way. 



