40i 
Scott— On Peduncle of Cycadaceae. 
stem had a typically mesarch structure. This was notably 
the case in Lyginodendron Oldhamium , where the very perfect 
preservation enabled us to examine the anatomy in great 
detail, and to prove that the bundles of the stem are precisely 
similar in organization to those of Cycadean leaves 1 . The 
same was the case in Poroxylon , as shown by the investi- 
gations of MM. Bertrand and Renault 2 . 
Heterangium agrees with Lyginodendron so far as the leaf- 
trace-bundles are concerned 3 ; and the Calamopitys Saturni of 
Unger, according to the recent investigations of Count Solms- 
Laubach, conforms to the same rule 4 . 
The frequency of mesarch structure in the stems of Palaeo- 
zoic plants showing unmistakable affinities with Cycada- 
ceae, renders it highly probable that this character formerly 
extended to the stem, as well as the leaf, of the Cycadaceae 
themselves. This consideration suggested a renewed investi- 
gation of the anatomy of recent Cycads, in order to ascertain 
whether some vestiges of mesarch structure might not still 
survive in the bundles of the stem. The inquiry thus under- 
taken at once led to the observation that in the peduncle 
of both the male and female cone of S t anger ia paradoxa , 
T. Moore, centripetal xylem is present, so that the structure 
of the vascular bundles in these axial organs is of the mesarch 
type 5 6 . This discovery has since been extended to the peduncles 
of certain other Cycads, namely Bowenia spectahilis , Hook., 
Zamia Loddigesii , Miq., and Ceratozamia mexicana G , Brongn. 
1 Williamson and Scott, Further observations in the organization of the Fossil 
Plants of the Coal Measures, Part III, Lyginodendron and Heterangium : Phil. 
Trans., Vol. 186, B, 1895, p. 713, Plates XXI and XXII. 
2 Recherches sur les Poroxylons : Archives Bot. du Nord de la France, 3me 
Annee, 1886, p. 382. 
3 Williamson and Scott, loc. cit. p. 749. 
4 Solms-Laubach, Pflanzenreste des Unterculm von Saalfeld : Abhandl. d. K. 
Preuss. Geol. Landesanstalt ; neue Folge, Heft 23, p. 65, Plate IV, 1896. The 
Calamopitys of Unger, which evidently belonged to the Lyginodendreae, must not 
be confused with the Calamarian stem described by Williamson under the same 
name : Mem. Lit. and Phil. Soc. of Manchester, ser. 3, Vol. iv, 1869. 
5 See Williamson and Scott, loc. cit. p. 768. 
6 In these three cases the centripetal xylem was first detected by my assistant, 
