Other Calamitean cones, and examples illustrating the connection between Cones and Vegetative Shoots.
It would be out of place in an introduction to Palaeobotany to attempt an exhaustive account of the various cones which were probably borne by Calamitean plants, but there are a few general points to which the attention of the student should be directed. The examples dealt with in the foregoing description illustrate the fact, that plants included under the comprehensive genus Calamites bore cones possessing distinct morphological features. There are, however, other types of strobili which have been found in organic connection with Calamites; and some of these must be taken into account in dealing with Calamarian plants. The genera Volkmannia, Brukmannia, Huttonia, Macrostachya, in addition to Calamostachys and Palaeostachya and others, have been applied by different writers to Calamitean cones. As Solms-Laubach[723] has suggested, it is wiser to discard Volkmannia and Brukmannia, as they have been made to do duty for cones of widely different forms. It is better to adhere to the provisional generic names used by Weiss, as they enable us to conveniently systematise the various Calamarian strobili.
The following classification may be given of the better known cones, some of which we are able to describe in considerable detail, while others are still very imperfectly known. We have good evidence that all these strobili were borne by vegetative shoots of the type of Calamites, Calamocladus or Annularia.
1. Calamostachys[724] (including Paracalamostachys and Stachannularia).
Cones long and narrow, consisting of a central axis bearing alternate whorls of sterile and fertile appendages, the latter having the form of sporangiophores attached at right angles to the axis midway between the sterile verticils, and bearing four sporangia on the inner face of a peltate distal expansion.
Calamostachys Binneyana Schimp., C. Ludwigi Carr., C. Casheana Will., may be referred to as examples of this type of cone; also some of the strobili described by different authors as species of Volkmannia[725], Brukmannia[726], &c.
Although one cannot make out the detailed structure of a Calamite cone in the absence of internal structure, it is often possible to recognise the essential features in specimens preserved in ironstone nodules, such as those from Coalbrook Dale in Shropshire, or by carefully examining the carbonised impressions on shale under a simple microscope.
Weiss applies the term Paracalamostachys[727] to cones of the Calamostachys form, but in which the manner of attachment cannot be made out. Such a cone as that of fig. 93 should probably be referred to this sub-type of Calamostachys in the absence of definite evidence as to the position of the sporangia.
Another term Stachannularia, originally used by Weiss as a genus[728], was afterwards[729] applied to cones of the same general type as Calamostachys, in which the sporangiophores have the form of thorn-like structures bearing on their upper side a lamellar expansion. There is however some doubt as to the correct interpretation of the features associated with cones included in Stachannularia; for an account of such forms reference must be made to the writings of Weiss, Renault[730], Solms-Laubach[731] and others[732].
Calamostachys cones have been found in organic union with branches bearing leaves of the Annularia type, also with Calamocladus foliage, and the branches bearing such cones have been found in actual connection with Calamitean stems. The association of cones and vegetative stems and branches is shown in tabular form on p. 363.