9L6 PROFESSOR W. CG. WILLIAMSON AND DR. D. H. SCOTT ON THE 
Carboniferous epoch. The arrangement and structure of the peltate sporangio- 
phores, so closely resembling those of Hgussetum, are typical of Culamariee, and 
indeed constitute the most essential characters on which that family has been 
founded. 
The question remains, however, to which, if any, of the known Calamarian stems, 
did the Calamostachys fructifications belong? At present the question must remain 
open, for the only way of answering it with certainty, would be to find stem and 
strobilus in connection, and this has not yet been done in the case of the species 
in question. 
So far as the anatomical evidence is concerned, there is no reason why astrobilus of 
the Calamostachys type should not have been borne on the stem of a Calamite, such 
as we have described in the first part of this paper. The differences in structure are 
no greater than we should be prepared to find between the axis of a fructification and 
a vegetative stem, and no greater than we actually do find between branches of 
different order in one and the same species of Equisetum. In some points, indeed, 
such as the presence of an intercellular space at the protoxylem of each bundle, and 
the structure of the nodal wood, the agreement is even surprisingly close. 
We have, however, to take account of the fact that a fructification of a different 
type has been proved, in previous memoirs, to have been that of a Calamites. The 
first specimen of this fructification was described in 1869.* Long subsequently other 
and more complete specimens were discovered, and a full account of the whole structure 
was laid before the Royal Society in 1887.1 We have re-examined the specimens for 
the purposes of the present paper, but, except in one point, have nothing to add to 
the previous descriptions. 
A summary, however, of the facts relating to this fructification must be given here, 
for the sake of comparison with the structure of Calamostachys. 
The strobilus of the “ Calamitean ” fructification was pedunculate, and consisted of 
an axis bearing numerous whorls of bracts, which were coherent for some distance 
from their insertion, the coherent part forming the “disk” of previous descriptions. 
The bracts after leaving the axis at a right angle, or with a slightly downward 
curvature, turned sharply upwards, their superior portions becoming approximately 
parallel to the axis. 
The sporangiophores were borne at the base of the coherent bracts, on their upper 
surface, and were thus very nearly axillary. They numbered sixteen, eighteen, or 
twenty in a whorl ; their direction was obliquely upward. The number of the bracts 
seems to have been double that of the sporangiophores. 
Each sporangiophore bore four sporangia, though it is not quite certain that this 
number was absolutely constant. They surround the pedicel of the sporangiophore. as 
* Wirtiamson, ‘Mem, Lit. and Phil. Soc. of Manchester,’ Series 3, vol. 4. 
t+ Wtrramson, “True Fructification of Calamites” (“ Organization,” Part XIV.); ‘Phil. Trans.,’ 
vol. 179, B. 
