10 Miss Robertson, Notes on the Anatomy of 



the central tissues. In the loose parenchymatous secondary xylem 

 a number of structures occur, which at first sight appear in 

 transverse section like concentric bundles ; closer examination 

 however shews that these are merely small islands of secondary 

 xylem excised by the formation of an anomalous periderm. Such 

 islands were seen in the remains of two roots of very different 

 sizes. 



In the stem anomalous periderm is also met with, especially in 

 the lower part. On cut surfaces small oval, circular, or quite 

 irregular areas, generally with a lighter coloured border, and a 

 dark or mucilaginous interior, are seen in the cortex, in and 

 between the vascular zones, and in the pith ; those in the pith 

 seemed to be confined to the peripheral part. (Fig. 6.) They are 

 mostly 2 or 3 mms. across, but some are 0*5 to 1 cm., and one at 

 the bottom of the pith is about 2 cms. long by 4 mms. wide, as seen 

 on one of the cut surfaces formed by dividing the trunk in half 

 longitudinally. When examined microscopically the pale border 

 is found to be a band of cork consisting of very narrow thin- 

 walled cells. A variable amount of phelloderm is cut off to the 

 exterior. Scattered in the phelloderm and the parenchyma im- 

 mediately outside it are a large number of cells, containing what 

 appears to be an orange gum. Inside the periderm the walls and 

 contents of the cells have commonly degenerated into a gummy 

 substance, and the centre of the patch is sometimes occupied 

 by a mass of starch grains. All the tissue inside the peridermal 

 sheath is generally more or less in a state of disintegration and 

 tends to fall out when sections are cut. 



The only explanation yet given of these curious peridermal 

 formations is that expressed by Scott 1 when he says, "It is in the 

 excision of effete tissues that we must seek the significance of 

 these anomalous developments." 



(viii) The Leaves. 



Close to the apex of the stem a very young leaf was found, 

 whose length, including the petiole, was less than 1 cm. The size 

 of the rudimentary pinnae could clearly be seen to diminish from 

 above downwards, so that their development is basipetal, as already 

 described by Bower 2 for the case of Macrozamia Miquelii. In 

 another leaf, 3 cms. long, the pinnae which at this stage shew the 

 double forking characteristic of the mature leaf, were lying fiat 

 against one another, and there was no sign of circinnate verna- 

 tion. The bases of the leaves are covered with hairs of the type 



1 " Medullosa anglica," Phil. Trans. Boy. Soc. Vol. 191, B, 1899, p. 97. 



2 " The Comparative Morphology of the Leaf in the Vascular Cryptogams and 

 Gymnosperms," Phil. Trans. Boy. Soc. 1884, p. 592. 



