162 



Mr Seward, Motes on the Binney Collection 



tracheids are shown at pos on the outer edge of the leaf-trace It ; 

 the curved and broader elements traversing the parenchymatous 

 tissue to the right of the protoxylem strands belong to the inner- 

 most part of the secondary xylem of the stem, and beyond these 

 we have the more regular reticulately pitted elements and medul- 

 lary-ray tissue (mr) of the secondary wood (& 2 ). The further 

 consideration of the peripheral tissues of the primary vascular 

 axis forms part of the description of the leaf-traces. 



At the periphery of the primary xylem of the stele — shown in 

 the transverse section, fig. 7, PI. VI. — there are rather more than 30 

 groups of narrow protoxylem elements. 



In longitudinal sections the greater part of the primary 

 xylem presents the appearance shown in text-figures 2, 3, 

 and 4 m, and in PL vil. fig. 9 ; the large and characteristic 

 tracheids are for the most part very short and somewhat 

 horizontally elongated elements with numerous bordered pits in 

 their walls; these are embedded in a mass of parenchyma which 

 on contraction has given rise to fairly broad radial gaps between 

 the firmer and more resistant tracheal groups. These spaces form 

 a conspicuous feature in longitudinal sections of the primary 

 xylem ; they may be seen as light horizontal patches in fig. 1, 

 PL v., and on a larger scale in text-figs. 2 and 3, especially in 

 fig. 2 in the region m, also in fig. 9, PL VII. ; they bear a striking 



x 2 It m 



Figure 2. Longitudinal Section showing the Edge of the Secondary Xylem 

 (x 2 ), a Leaf-trace (It), and the Metaxylem (hi). (Section I. 8, x 16.) 



superficial resemblance to the more regular discoid pith of Cordaites, 

 which it is possible may also be largely if not entirely due to 



