34 MR ROBERT KTDSTON ON 



It may not be without service to review as shortly as possible the evidence on which 

 these two opinions as to the affinities of Sigillaria have been founded. Other views 

 which referred Sigillwria to the Cactacecs and Euphorbaceoe need not be discussed, as 

 they arc utterly untenable. 



The small specimen of Sigillaria, whose internal organisation was described by 

 Brongnjart in 1839, under the name of Sigillaria elegans* consisted of a small part of a 

 young stem about 2 cm. Ions; and 4 cm. in diameter. 



The most of the delicate tissue lying between the central vascular bundle and the 

 bark had disappeared, but the denser cortical portion and the vascular system were 

 excellently preserved. The specimen therefore presented an outer cylinder of bark and 

 an inner cylinder of vascular tissue, between which originally lay a delicate cellular 

 tissue, of which only a few fragments were preserved. 



The outer cortical cylinder, constituting the bark, and on whose outer surface were 

 the rhomboidal leaf-cushions, was composed of very fine and very dense fibro-cellular 

 tissue. The more important portion of the stem — the vascular system — formed a 

 perfectly regular hollow cylinder, 13 to 14 mm. in diameter, but the cylinder itself is 

 only about 1 mm. in thickness, and composed of a definite number of bundles, always 

 perfectly equal and similar, and placed beside each other without almost any appreciable 

 interval, but distinctly individualised by their round interior margins, which gave a 

 " festoon " appearance to the inner boundary limit of the vascular system. Each of these 

 bundles is formed of two distinct zones — the inner and primary bundles forming the 

 '" festoon " structure, the outer and much larger portion the exogenously developed zone. 



In transverse section the primary bundles have the form of a segment of a circle 

 whose convexity points towards the centre of the stem, and are composed of vessels 

 irregularly placed without any order, whose walls are transversely or obliquely barred 

 or even reticulated. The larger vessels occupy the inner portion of the bundle, while 

 the smaller elements are placed externally. 



The exogenous zone is composed of vessels disposed in radiating series, sometimes 

 si | m rated by a narrow interval, which was occupied by the medullary rays, though these 

 were generally destroyed in the specimen. The vessels on the inner portion of the 



Egenous zone are smaller than those on its outer surface ; the smallest vessels of the 

 secondary zone being in contact with the smaller vessels of the primary bundles, and 

 these vessels of smaller size form by their contact, but without any confusion, a line of 

 demarcation between the primary and the exogenously developed bundles. 



Outside of the exogenous zone, and situated close to it, are small isolated lenticular or 

 circular bundles composed of uniform tissue, but smaller and disposed without any order. 

 These are the foliar bundles. 







* This specimen was namerl .S'. dajans by Buongniart in error. The fossil is his Sig. Menardi, Hist. d. vfyit.foss., 

 pi. clviii. fig. <> (? not fig. 5), which again is only a young condition of Sigillaria Brardii, Bgt, the type of the 

 Ulathraria section of Sigillaria. See Zeiller, Ann. d. Scienc. Nat., 6°. ser., "Bot.," vol. xix. p. 259, 1884 ; Welsh, 

 Hitz-Berichi 'I. Gesell. natur. Freunde. Berlin, No. 5, 188G, p. 7<>. 



