62 
PEOEESSOE W. C. WILLIAMSON ON THE OEGANIZATION 
Mr. Carruthers has described the wall of the sporangium as “ composed of irregularly- 
elongated cells, with projections of a secondary deposit extending at right angles into 
the interior of the cells.” This is strictly correct ; but there is something beyond this 
to be noted. The longer axes of these cells are radial in relation to that of the fruit- 
axis, and parallel with the longer sides of the sporangium. When we see only the outer 
surface of the sporangium-wall, we observe that the latter appears as represented in 
Plate VI. fig. 39, and by Mr. Caeruthers in his fig. 5 ; but its inner surface frequently 
exhibits the aspect seen in Plate VII. fig. 42. When a transverse section, like Plate 
VII. fig. 40 (again represented by Mr. Caeruthers in his fig. 45), is made across the 
shorter diameters of these cells, we see that each cell has very thick walls on its inner 
and two lateral surfaces ; whilst the outer wall, forming part of the outer surface of the 
entire sporangium, is very thin. But if the section is made through the long axes of 
these cells, so that their lateral walls are brought into view, we then obtain the appear- 
ance indicated by Plate VII. fig. 41, where the parallel bars are much more numerous 
and more perfectly parallel in their arrangement than in Plate VII. fig. 42. The bars 
in fig. 40 are obviously different from those of fig. 41. The former represent the cell- 
walls of a corresponding number of distinct cells ; the latter represent the transverse bars 
thickening the walls of one individual cell. It is obvious that we have here a modifi- 
cation either of the spiral or of the annular cell ; but instead of the lignine, forming the 
thickened bars of Plate VII. figs. 41 & 42, being continued entirely round the transverse 
circumference of the elongated cell, some unknown influence has prevented their depo- 
sition on the outer surface of every cell — a curious example of the effect of unknown 
forces in regulating the distribution of these secondary deposits in fibro-vascular 
structures. 
Mr. Carruthers has represented in his fig. 1 a cluster of spherical spores, from the 
outer wall of each of which there project delicate thread-like appendages. He describes 
these as follows : — “ The spores are simple globular bodies, frequently exhibiting an outer 
and an inner wall. Sometimes, however, they appear to be composed of a single wall, 
and then the outer wall is represented by lines more or less separated from the spores. 
These I believe to be elaters, similar in structure to those of Equisetum” As to the 
first of these statements respecting the outer and inner walls, my observations agree with 
those of my indefatigable friend, but from his elater hypothesis I am compelled to dissent. 
The following appears to me to be the probable explanation of these appearances. 
Plate VII. fig. 43 represents a number of these spores selected from two strobili in 
different stages of development. The larger ones exhibit a series of examples in which 
we have an inner cell enclosed within an outer one. Of these, Plate VII. fig. 43, ware 
the forms which approach nearest to the condition in which Mr. Carruthers recognizes 
elaters. In these specimens the point of contact between the inner and outer cells repre- 
sents, according to his view, that at which the elaters of an Equisetiform spore are 
united to the actual spore ; but the other examples figured show that this contact is 
accidental and not essential. In most of them the spore lies free in the centre of the 
