358 NATURAL SCIENCE. May, 
to are very explicit, and leave no doubt that the former alternative is- 
the true one. 
In the next place, it became clear that the axis differed in a 
much more important point from the published descriptions of it,. 
and that in a direction which had not been previously suspected. In 
fact, the specimens proved to demonstration that the cellular pith is. 
surrounded by a ring of primary vascular bundles, which, in essen- 
tials, are of the true Calamitean type. The number of these is. 
usually three, though there may be four or more, but, whatever be 
the number, each is characterised by the presence, at the apex of the 
xylem, of a carinal canal homologous with the canals found in the 
same position in the stems of Calamites and Equisetum, and which 
represent the tracheal initial strands of the primary vascular bundles.. 
In the transverse sections, we find individual elements clinging to: 
the sides of the canals, and projecting into their cavities, reminding 
us at once and forcibly of the appearances met with in Eguisetum. So: 
close is the resemblance, that one might from the transverse sections 
alone infer that these projecting elements are annular or spiral 
vessels, but for demonstrative proof recourse must be had to the 
longitudinal ones. Fortunately, some of these have been made in 
such favourable directions, and the tissues are so well preserved, that 
they leave nothing to bedesired. They show us the carinal canals cut 
throughout their whole length, with the annular vessels still attached 
to the peripheral walls. 
Hence it is obvious that the stele or central cylinder of the axis. 
of Calamostachys Binneyana has a structure which is identical in essen- 
tials with that found in the stem of Calamites, and there is no such. 
antagonism between the anatomy of the two as has hitherto been 
believed. Not only so, but when, as sometimes occurs, the forma- 
tion of secondary xylem begins, it does so first at the carinal canals, 
as in Calamites, and subsequently in the intervening areas. In this. 
way is brought about the triangular form of the pith, and the 
triquetrous arrangement of the vascular laminz which surround it, 
and which Williamson compared with the secondary xylem of the 
plant he named Astevophyliites. 
The conclusion, then, is, that the correspondence between the 
anatomy of the stem of Calamites and the axis of Calamostachys 
Binneyana is so close and definite as to leave no doubt whatever 
that the one is the fruit-spike of the other. Williamson’s objections 
to this determination have all been based upon the supposed 
absence of such a correspondence, and now that it is shown to 
exist they naturally fall to the ground. The internal anatomy of the 
spike, then, points to the same affinities as the external characters, and 
together they supply all the evidence that is needed to establish the 
conclusion we have stated. To which ofthe forms of Calamites the spike 
is to be more particularly referred cannot at present be definitely 
stated, but there are some reasons for thinking that it must be sought 
