OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
295 
Lycopodiaceas, having a thickness at their respective bases of about *022 ; but they soon 
subdivide into smaller branches, which generally proceed to different sporangia. Though 
the latter are very much more numerous than the primary bracts, each sporangium rests 
upon its own special branch of a bract. The sporangia (u) exhibit in this section a wedge 
shape. The small peripheral sporangia (id) seen in the figure are merely the tips of 
the next contiguous ones rising up from below, in consequence of their slightly oblique 
and ascending plane not corresponding with the horizontal one of the section. Plate 
XLIV. fig. 24 is a tangential section of another specimen, which exhibits the oblique 
spiral arrangement of the sporangia characterizing the taxis of these fruits. At t we 
have the free extremities of the subdivided bracts. Fig. 25 represents a small portion 
of fig. 24 more highly magnified, and exhibits with remarkable clearness the shape of 
the subdivided bracts, and the way in which the latter are attached to their respective 
sporangia. The perfect sporangium (u) occupying the centre of this figure may be 
accepted as a type of the structure of these organs and of their relations to the bracts. 
Each sporangium is enclosed in a cellular sporangium-wall (v), which, when viewed 
superficially, appears composed of ordinary parenchyma, but when seen in section 
exhibits these cells elongated vertically, the structure closely resembling a corresponding 
section of a piece of honeycomb. Sometimes one cell extends from surface to surface, 
at others two cells of equal diameters are piled linearly upon each other. The average 
thickness of these sporangium-walls is ’0075. The shape of the transverse sections of 
the secondary bracts is shown in the three dark-coloured objects (fig. 25, t), especially in 
that supporting the central sporangium. The upper surface is rounded and prominent, 
fitting into a corresponding depression in the under surface of the sporangium. On each 
side of this the bract spreads out into a thin horizontal expansion, concave superiorly ; at 
its inferior surface a deep thin keel runs along the entire length of the bract and dips down 
between the two contiguous sporangia of the series immediately below, as if designed to 
steady the several segments of the strobilus. From the interior of the raised dorsal surface 
a similar but smaller and thinner vertical lamina rises, the upper part of which ascends 
into the sporangium and is imbedded amongst the spores; its uppermost margin is bifid, 
the two diverging parts being recurved in opposite directions outwards and downwards. 
This ascending portion, obviously the true sporangiophore, is of so delicate a texture, 
especially at its upper part, that it can only be distinguished from the surrounding spores 
by its denser aspect. The delicate lines id in fig. 23, which appear as continuations 
of the large bracts, are longitudinal prolongations of the same sporangiophores, which 
appear to be coextensive with the entire length of the sporangium. The sporan- 
gium-wall is inserted into the bract close to the base and at each side of the sporangio- 
phore. It first arches upwards as it approaches the latter organ, and then, suddenly 
descending, it plunges vertically into the bract, with the parenchyma of which its own 
cells become intermingled. It thus appears that each sporangium is not only sustained 
by its own bract, but is united to that bract throughout its entire length in the firmest 
manner. I have not been able to ascertain the actual forms of the peripheral extremities 
