218 A. C. Seward — Telodendron and Voltzia. 



2. — Tylobexduon, Weiss, and Voltzia ueterophylla, Bkongn. 



IN 1869 Prof. Weiss instituted a new genus Telodendron, which 

 he defined as follows: 1 — " Plantae arboreae, amplis interval lis 

 ramosae. Rami teretes, longi crassique, obtuse terminati, pulvinis 

 rhonibeis plus minusve elongatis et acuminatis spiraliter dispositis 

 aequalibus vel repetito-abbreviatis tecti. Pulvinorum pars superior 

 sulco acuto ab altissima pulvini parte oriente in crura bina parallela 

 contigua longissinia divisa. Corpus ligneus vasa porosa poris 1-, 

 2-, 3-seriatis confertis et radios medullares notatos exhibens ; annuli 

 lignosi inconspicui." 



The general characteristics' of the genus are considered to be those 

 of a Conifer; 2 the only point in which a difference exists being the 

 presence of a slit in each of the elongated areola? : this slit Weiss 

 regards as an indication of the former existence of a resin-canal, like 

 those which occur in the leaves and stems of our recent Conifers. 

 It is suggested as possible 3 that the present surface of the fossil, 

 which is covered with rhombic areola?, may represent the internal 

 cast of a stem. 



Dr. Potonie, of Berlin, contributed a paper to the " Jahrbuch der 

 Konigl. preuss. Geologischen Landesanstalt for 1887, p. oil, 4 in 

 which he gave the results of a detailed examination of several speci- 

 mens and sections of Tylodendron ; he arrived at the conclusion that 

 Tylodendron is not the wood, but the pith of a Conifer, probably 

 that of an Araucaria. Artisia is referred to as a similar case of 

 a pith-cast, whose true nature was first brought to light by an 

 examination of sections showing internal structure. Pith-casts of 

 Stigmaria occur which bear a close resemblance to Tylodendron. 

 Potonie cites figures given by Williamson 5 as instances of such 

 casts : fig. 65 of Williamson's monograph shows, for example, not 

 only similar rhombic areola?, but also the slits extending along half 

 the length of each areola as Tylodendron. Weiss has figured his 

 specimens of Tylodendron in an inverted position, he regarded the 

 pointed end of the specimen in Tab. xix. and xx. as representing the 

 tapering off of the stem towards the upper end : as a matter of fact, 

 according to Dr. Potonie, the slit extends from the loiver end of each 

 rhombic areola, and marks the position of the foliar bundles, as that 

 in Stigmaria shows the position of the rootlet bundles. 



Dr. Potonie has examined a large number of recent conifei*ous 

 stems, and finds that a cast of the medullary cavity of Araucaria 

 brasiliana closely resembles small specimens of Tylodendron. 6 I 



1 " Fossilen Flora der jungsten Steinkohlenforination und des Pothliegenden ira 

 Saar-Khein-gebiete," p. 182. 



2 Parkinson figures a fragment of what appears to be Tylodendron ; no locality is 

 mentioned, see " Organic Remains of a Former World," vol. i. pi. iii. fig. 4. 



3 Fossilen Flora der jungsten Steinkohlen, etc., p. 183. 



4 " Ueber die fossile Planzen-Gattung Tylodendron.'''' Three plates accompany 

 this paper, illustrating the external appearance and microscopic structure of Tylo- 

 dendron. 



5 "A Monograph on the Morphology and Histology of Stigmaria Ficoides. 

 (Palseontographical Society, 1887), pi. xiii. figs. 64 and 65. 



6 Potonie, loc. cit. Taf. xiii. a. 



