Benson.—Mazocarpon or the Structural Sigillarioslrobus. 571 
adavial groove, o-n 
tract* 
(Fig. 15), and strands of apparently lignified cells would appear to be present 
in others also, e.g. H. Cn. 519, 4 and 5, but are there cut transversely. 
In immature sporangia, e.g. those in the Manchester slide (see Fig. 15), 
the germinating spores lie in tissue which markedly differs from the pad and 
certainly suggests barren sporogenous tissue. On this abut the tubular 
tapetal cells which grow centroscopically into the sporogenous region 
which they surround. A few of these can be seen in several figures (Fig. 16), 
but they reach an extraordinary development in an abortive sporange 
(Fig. 7) and in the microsporange (Figs. 13 and i$a). In the latter the 
repeated serial divisions of the tapetal cells give a most unusual appearance 
to the sporange. 
The mature sporange shown in Fig. 18 measures slightly over 5 mm. 
in length, and 2-6 mm. in height. 
These are approximately the 
dimensions, as we shall see later, 
of Dr. Kidston’s incrustation 
specimen of the sporange of 
Sigillariostrobus ciliatus} with 
which the new petrifactions 
agree also as respects the size, 
surface, and probably the form, 
of the spores. The sporangia 
occur occasionally in an almost 
intact condition free from the 
cone-axis—such are those of 
Figs, i, 6, 13,17, and 18. The 
abortive specimens, also, which 
are shown in Figs. 5 and 7, 
were lying free from any cone- 
axis. Thus we may regard the 
sporophyll as liable to fall off 
even in an immature condition 
of the gametophyte or 4 spore 5 
(Fig. 15)- Not only did the sporophyte as a whole fall,but the sporange seems 
to have broken up very easily into pieces, each consisting of a ‘ spore ’ and 
a piece of the thick sporange-wall attached to its base (Fig. 9). 
The characteristic formation of a distal lamella, into which the convex 
base of the bract above must have fitted, was probably a contributory 
factor, as will be shown later, to the rupture of the sporange. Distally the 
lamella springs from the base of the sporange, but from a higher level at the 
sides (Text-fig. 1). In the third, or middle, member of a series of five 
1 See Kidston, loc. cit., Plate II, Figs. 3 and 3 a (or consult Scott’s Studies in Fossil Botany, 
Fig. 96 b, p. 234). 
Text-fig. 
gram from a 
Mazocarpon. 
r. Explanation in the text. A dia- 
model of the megasporange of 
