918 PROFESSOR W. C0. WILLIAMSON AND DR. D. H. SCOTT ON THE 
latter specimen the relative position of the bracts and sporangiophores is all but 
identical with that in the English fossil. The chief differences are that the bracts in 
Paleostachya gracilis are less extensively coherent, and that the insertion of the 
sporangiophores is more exactly axillary, and less adherent to the bracts themselves. 
In both plants the number of the bracts is double that of the sporangiophores. 
The anatomy of the stem in Paleostachya gracilis, as shown in M. Renavtt’s 
figures, has quite a Calamitean character. The medulla is fistular, and the vascular 
bundles ave accompanied by their usual canals. The number of the bundles here also, 
is equal to that of the sporangiophores. 
In M. Renavutr’s plant the peltate scales are perfectly preserved ; their structure 
and the mode of attachment of the sporangia are manifestly the same as in 
Calamostachys. 
The character of the genus Palwostachya, as defined by WEISS, is as follows : 
‘‘Sporangiophores arising from the axil of the bract, or its immediate neighbourhood, 
ascending obliquely.”* 
As this definition applies both to the Calamitean fructification of WILLIAMson, and 
to the Volkmanma gracilis of RENAULT, we may speak of this type as the Paleostachya 
form of fructification. As however the English specimens are so obviously strobili of 
Calamites, we do not propose to give them a distinct generic name, but to distinguish 
them as Calamites pedunculatus, which is thus the equivalent of the “true fructification 
of Calamites,” described in previous memoirs. 
We have now to discuss this question: Are the differences between the 
Calamostachys and the Paleostachya types of strobilus so great that they cannot have 
belonged to closely allied plants ? 
The essential differences are two : (1) in the position of the sporangiophores, which 
are approximately axillary in the Paleostachya type, but are inserted midway between 
the whorls of bracts in Calamostachys ; (2) in the anatomy of the axis, which is 
completely Calamitean in the Paleostachya strobilus, while Calamostachys differs in 
the small number of vascular bundles, and in its relatively small persistent pith. 
A form described by M. Renautr under the name of Bruckmannia Grand’ Euryi 
(the Calamostachys Grand’Euryi of Waiss’s nomenclature) seems to bridge over the 
gap in a very satisfactory manner.t In this species the arrangement of the sporan- 
giophores is exactly that of a typical Calamostachys; they form independent whorls, 
inserted midway between the verticils of bracts. Their structure, also, is identical 
with that of the sporangiophores of C. Binneyana. The anatomy of the axis, 
however, is that of a Calamite. The medulla is large and fistular ; the numerous 
bundles surrounding it have well-defined canals. It appears, then, that in this species 
the external morphology of Calamostachys co-existed with an anatomical structure 
identical with that of Calamites or Paleostachya. 
* ‘Steinkohlen-Calamarien,’ vol. 2, 1884, p. 161. 
¢ Rovavrr, ‘Ann. Sci. Nat., Bot.,’ Sér. 6, vol. 3. Plates 3 and 4. 
