ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 937 
The Bracts. 
In transverse sections passing through the base of the disc, or coherent whorl of 
bracts, we find the out-going bundles again, just where they leave the cortex, and 
pass out obliquely into the verticil (see Plate 85, fig. 55, which is from the same 
section as the more general figure in WiLL1aMson, Part XVIII. Plate 27, fig. 9). 
At this point each bundle undergoes a division into three. One branch, the most 
external of the trio, continues its course through the disc; the two others are given 
off on the inner side, towards the axis, and supply two sporangiophores (compare 
figs. 55 and 56, on Plate 85). The external branch in each case runs straight out 
through the disc into one of the free bracts, each of which always contains a slender 
vascular bundle, a fact which has been previously overlooked. 
The bundle-system of the appendages then, is clear; each bract receives a single 
bundle from the axis ; immediately on entering the verticil the bundle gives off two 
branches in an upward and inward direction, These branches constitute the bundles 
of the two sporangiophores corresponding to the bract in question. The determination 
of this fact supplies the answer to a question raised by M. ZerLueR in his memoir 
above cited,* as to the relation between bracts and sporangiophores. The anatomy, 
as well as the external morphology, indicates plainly that the sporangiophores are 
appendages of the bracts, and not independent outgrowths of the axis. 
As regards the structure of the bracts, a few words will suffice. In the coherent 
portion of the whorl the parenchyma is, on the whole, very uniform, except that we 
find a palisade-like layer near the insertion of the whorl and towards the lower 
surface (Plate 85, fig. 54). The xylem of each vascular bundle is surrounded by an 
empty space, which no doubt marks the position of the phloém and thin-walled tissue. 
It is not possible to determine whether the bundle was collateral or concentric. 
The free bracts have a well preserved epidermis, in which smaller cells are seen 
here and there, but no definite stomata can be detected. Usually only the middle 
part of the mesophyll is preserved ; towards the edges of the bract the space within 
the epidermis is empty. Through the middle of the persistent central tissue runs 
the slender vascular bundle, which can only be well seen in the most favourable 
sections. In other respects, a previous figure gives a sufficient idea of the structure.t 
The Sporangiophores and Sporangia. 
The insertion of the sporangiophores, as determined by the point at which their 
vascular bundles are given off from those of the bracts, appears to be constant, while 
the amount of adhesion, beyond this point, between the sporangiophores and the 
coherent disc, is very variable, as has already been explained. 
* Loo. cit. p. 21. 
+ WiiiaMson, loc. cit., Part XVIII, Plate 27, fig. 12. 
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