1858.] BIN1«^EY STIGMARIA. 77 



points of considerable interest, and whicli up to the present time 

 have not been well determined. 



First, as to the origin of the medullary ray, and the nature of the 

 vascular bundles in the pith — Dr. Joseph Dalton Hooker, in summing 

 up the state of our knowledge of Siigmaria^, in 1848, describes the 

 woody axis of the root, and figures two characteristic specimens, one 

 showing the large meduUary rays or bundles, and the other the 

 narrow rays. The author then says: ''the medullary rays, even the 

 narrowest, are traversed by bundles of tubes, half the diameter of 

 the largest vessels of the axis (or wood), or even less (pi. 2. figs. 6, 

 7a, and 8). The transverse lines on their surface are generally 

 finer and less crowded. These bundles evidently originate in the 

 cellular axis of the stem, and do not belong to the wedges of vas- 

 cular tissue (or wood) between which they run, as they appear to 

 have done in M. Brongniart'sf specimen of the plant, both from his 

 figure and description. I cannot, however, but conclude the latter 

 to be erroneous, because M. Goeppert, whose specimens appear to 

 have been in this respect more perfect than any hitherto illustrated, 

 represents the bundle of vessels which proceed from the axis, run 

 between the wedges of wood, and communicate with the rootlets 

 (leaves, Goepp.), as originating in isolated bundles irregularly 

 scattered in the medullary axis of the stem. Of the existence of 

 these bundles there are some indications in my own specimens, 

 though for the most part they have been destroyed by the cellular 

 tissue of the plant, which indeed often takes place with the system 

 of vessels from which the leaves, rootlets, or scales of the cones in 

 the fossils are supplied. It is so in the stems of Lepidodendron, in 

 the axis of Lepidostrobi, in the portion of the Sigillarice figured by 

 M. Brongniart, and in other fossils contained in the Museum of the 

 Survey, and is probably owing to their great delicacy, for they are 

 much more membranous in appearance than the similarly-marked 

 vessels of the wood. 



The most important circumstance thus developed is the existence 

 -of a double system of vessels in Stigmaria, first shown by Goeppert, 

 and the consequent approach, in this respect, to DiploxylonX, Corda. 

 In Diploxylon, however, the inner system forms a continuous cylinder, 

 concentric with and in juxtaposition to the wedges of wood forming 

 the outer ; whilst in Stigmaria the same inner system is broken up 

 into scattered bundles, apparently unsymmetrically arranged in the 

 medullary axis or pith of the plant. 



1. Now, as to the medullary rays oi Stigmaria coming direct from 

 the axis of the stem, and not originating in the vascular cylinder, 

 as supposed by M. Brongniart, a specimen in my cabinet (PL lY. 

 fig. 18) shows this most decisively, and fully confirms Dr. Hooker's 

 views as hereinbefore quoted. In this specimen the woody cylinder 



* " On some pecuKarities in the structure of Stigmaria," by Dr. Hooker, 

 F.R.S., and Botanist to the Geological Survey of the United Kingdom ; Memoirs 

 vof the Geological Survey, vol. ii. Part 2. p. 434. 



t Archives du Museum d'Hist. Nat. vol. i. p. 405, t. 29. t^d. 



X Corda, Flora der Vorwelt, p. 34, pi. xi. 



