148 Mr Seward, Notes on the Binney Collection 



As in Section 1 the peripheral tissue is traversed by a crack 

 approximately corresponding with the junction of the broad middle 

 and the narrower outer cortex; but in this section a secondary 

 tissue or phelloderm has begun to be formed in the outer cortex 

 (PL iv. fig. 6 pi.); the phelloderm consists of radially disposed rows 

 of rather thicker walled cells, about six deep, and here and there 

 the outer cortex is traversed by radially elongated spaces which 

 were originally occupied by leaf-traces and their accompanying 

 thin- walled parenchyma. Another feature of interest in this part 

 of the stem is the presence of groups of dividing and partially 

 disorganised cells (fig. 6, PI. iv. sc) occurring at fairly regular 

 intervals immediately internal to the phelloderm ; these groups 

 undoubtedly mark the position of incipient canals or secretory 

 passages. Similar strands are represented by Bertrand 1 in Lepi- 

 dodendron Harcourtii, and excellent examples of the same struc- 

 tures occur in Lepidophloios Wunschianus from Arran and in the 

 large Dalmeny stem already alluded to. 



The longitudinal section, which is mounted on slide no. 2 

 with the transverse section, was cut from the same stem. A few 

 cells only of the pith are preserved ; these are arranged in regular 

 vertical series and their cavities are bridged across by transverse or 

 oblique walls of recent origin. The tracheids at the edge of the 

 corona are often characterised by a looser form of scalariform 

 thickening or by more or less spiral bands ; beyond these there 

 are about 12 rows of very short parenchymatous cells constituting 

 the meristematic zone, the outermost of which are in some cases 

 radially elongated and traversed by newly formed cross-walls (cf. 

 Text-fig. 2, m). These dividing meristematic cells pass outwards 

 with the leaf- traces on their inner side, as shown in fig. 9, PI. iv., 

 where the outermost cells on the left of the drawing represent a 

 strand of meristematic tissue accompanying a leaf-trace. The 

 direct continuity of the strand of disorganised secretory tissue s 

 (fig. 9, PL IV., and fig. 5, PL in.), which forms part of each leaf-trace, 

 with the secretory zone of the stem (PL III. fig. 3, s, s; PL IV. fig. 

 12) is clearly demonstrated in Section 2. The leaf-traces in this 

 section are seen to pass steeply upwards for a short distance after 

 they become free from the corona, and then bend almost at right 

 angles through the middle cortex, finally bending slightly upwards 

 in the outer cortical region ; their course differs from that of the 

 leaf-traces in Sections 1 and 4 (cut from the same stem) where 

 they follow a much steeper and obliquely vertical course. The 

 photograph reproduced in PL III. fig. 5 represents an outgoing 

 leaf-trace as seen in the transverse segment of Section 2 ; it is 

 shown in oblique longitudinal view ; at x we have the group of 



1 Bertrand (91), PI. iv. fig. 25. 



