726 MR W. T. GORDON ON 



In PI. TV. fig. 44 the pinna-traces are cut very obliquely, but it is obvious that they 

 would be almost circular in outline had they been cut transversely. In fig. 45 of the 

 same plate, the section above fig. 44 is shown. The pinna-trace on the right-hand side 

 is cut almost longitudinally as it is passing into the pinna. The trace on the left-hand 

 side has already passed out. These traces really pass out on the same level, but this 

 section is not perfectly transverse. 



The smaller pair of bundles, derived by division of the same bar as gave rise to the 

 pinna-traces, are also seen in figs. 44 and 45. In fig. 44 they have each bifurcated 

 (apli, tr.). One branch of each bifurcation passes rapidly through the cortex of the 

 petiole to the outside, while the other branches continue for some distance further in 

 the petiole and then they also bend suddenly outwards. The presence of large aphlebise 

 in this position supports or buttresses the departing pinnae, which are each almost as 

 large as the petiole they sprang from. 



Each primary pinna-trace passes into a separate pinna ; neither is atrophied ; then 

 each gives off traces, alternately on either side, to supply the secondary pinnse. In 

 PI. IV. fig. 48 one of the pinna-traces is seen. At the lower left-hand corner is one of 

 the secondary pinna-traces (pi), on the right-hand side of the primary pinna-trace 

 another secondary trace (p 2 ) is seen, while a third (p 3 ) has just become detached on the 

 left-hand side. 



The tissues of the' petiole, external to the xylem, are occasionally well preserved. 

 This is especially true of the specimens found isolated in the tuffs at Pettycur House. 

 In the specimen figured in PL IV. fig. 46 there is a layer, two to three cells deep, on the 

 inner side of the arms, which consists of very delicate tissue of small elements. Probably 

 it is due to the xylem of the arms offering some protection to this tissue against decay 

 that it is preserved at all. In the island of parenchyma enclosed by the arms of the 

 petiole-trace we also find the inner cortex to some extent preserved. Outside the layer 

 of delicate tissue referred to, there is a zone of decayed tissue probably representing the 

 phloem and other stelar tissues. Outside this, patches of cellular tissue are occasionally 

 preserved ; these patches consist of delicate parenchyma and are the remains of the inner 

 cortex. One patch is shown in PI. IV. fig. 46, i.e. This inner cortex probably extended 

 all round the petiole stele, filling in the clear space usually seen between the petiole-trace 

 and the outer cortex. The outer cortex forms a stout zone surrounding the more internal 

 tissues, and may be divided into two parts, an inner and an outer. The inner consists 

 of typical thick-walled parenchyma, and the outer consists of sclerotic cells. The 

 sclerotic outer cortex is figured in PI. IV. fig. 50, and the inner portion of it can be 

 distinctly seen in PI. IV. fig. 46, and also fig. 43. 



Histology of the Root. 

 The examination of the root has proved less satisfactory. It is small in diameter 

 compared with the stem (PI. I. fig. 4, rt. tr.), but very large for a root. Usually great 

 numbers of these roots are seen detached and scattered all through the block, but one 



