or THE EOSSIL PLANTS OE THE COAL-MEASUKES. 
61 
in the radial direction. At its outer extremity the two sides of each sporangiophore 
diverge in very regular curves, the peripheral intervening space (v f ) being occupied by 
a mass of parenchyma which, especially at v', v", and v"', is seen to constitute disks of con- 
siderable thickness. The same appearances recur in whatever direction the section is 
made ; hence my specimens confirm Mr. Carruthers’s statement, that these sporangio- 
phores correspond very closely with those of the living Equiseta , and do not sustain Mr. 
Binney’s opinion, that the sporangia are enclosed in “ six heart-shaped bags.” These 
sporangiophores undoubtedly contain barred vessels, since, like Mr. Carruthees, I have 
found them in the pedunculated portion of the organ ; and they are still more copiously 
developed where its two surface-layers diverge in regular curves to embrace the 
peripheral extremities of the sporangia attached to its opposite sides. That the 
sporangia adhere by those outer extremities to the proximate concavities formed by 
the inner surface of the terminal disks of the sporangiophores is certain. Hence, 
when a section is accurately made in the central plane of a sporangium, detached from 
the sporangiophore, as at fig. 36, u the outer end of the sporangium is always the part 
ruptured. The transverse sections of the leaves of the next inferior foliar disk are 
represented in the above figure at 1 1, and the tips of those of the next but one at t'. 
Plate VI. fig. 37 represents another transverse section of the fruit, made across the 
internode between a foliar Q disk and a verticil of sporangiophores, from the same specimen 
as Plate VI. fig. 36. We here find the vascular axis surrounded by a small double 
cortical ring, 1c. The sporangia are now reduced to twelve, showing that the verticil of 
sporangiophores to which they were attached were but six in number. Hence it 
appears that variations from six to seven sporangiophores may coexist in contiguous ver- 
ticils of the same strobilus. The sporangia (u) are here arranged Avith great regularity ; 
and seven of the twelve exhibit that rupture of their outer ends to Avhich I have just 
referred. The thin margins of the sporangiophores are seen at v, and a circle of the 
sections of the leaf-tips at t. 
The central vascular axis of this specimen exhibits an important feature, which 
has not been recorded in any of the specimens described either by Mr. Binney or 
by Mr. Carruthees; and as the section fig. 37 shows the peculiar structure very 
clearly, I have further enlarged it in Plate VI. fig. 38. The centre of this section is 
composed of a cluster of barred vessels grouped in the usual way ; its periphery 
consists of a ring ( d ) of similar vessels, but arranged in radiating laminae, and which evi- 
dently represent an exogenous growth superadded to the central bundle. I have never 
met with this condition in any other specimen, but the presence of this circumferential 
growth is important. It will be noticed that many of the radiating laminae follow a curvi- 
linear direction, and that the inner extremities of those laminae manifest a decided 
tendency to bend inwards towards the respective central points opposite to cl d. What 
their condition may have been at d' I cannot tell, because some accidental pressure has 
disturbed their natural arrangement here. I shall call attention to this peculiar dis- 
position after examining the root-structures of Aster ophyllites. 
