L62 



EDWARD C. JEFFREY ON 



Calamites. 



The Calamites first make their appearance in the Silurian deposits (Stur, Sitzungs- 

 berichte akad. d. wissensch. Wien, bd. 83, p. 40D) but their petrified relies and casts are 

 so rare in these earlier strata, that the upper Devonian and lower Carboniferous beds give 

 us the first definite idea concerning the organization of the more primitive representa- 

 tives of the group. One of the oldest Calamites of which we possess any detailed infor- 

 mation is the genus Archaeocalamites Stur. (Stur. Abh. d. k. k. geol. reicbsanstalt, 

 Wien, bd. 8. Heft 1. Culm-flora d. mahrischen-schlesischen dachschiefers. Heft 2 

 Culm-flora d. ostrauer u, waldenburger schichten.) In this form there is present the 

 jointed stem which is characteristic of the modern Equiseta. The ridges and channels 

 of the stem, however, differed from those of Equisetum in not alternating at the nodes. 

 The leaves which originated in the nodal region and were not united into sheaths, but 

 were quite free from one another and dichotomously divided. The roots also appeared 

 in relation to the nodes and were often forked like the leaves. Branches were frequently 

 present in the nodal region, but they do not seem to have been very numerous. Of 

 the nature of the strobili of this genus, very little is known, as they have been very 

 imperfectly preserved. The vascular frame-work, with which we are fairly well 

 acquainted, as the result of the investigations of Goppert, Renault, and Solms-Laubach, 

 had the same general features as that of Equisetum, differing only in its continuous 

 strands, and its secondary growth in thickness by means of a typical cambium. 



The Calamites proper, differed from Archaeocalamites in their generally undivided 

 leaves, and the continually more pronounced (in more recent strata) alternation of their 

 vascular strands at the nodes. They possessed, like the older type, a cylinder of second- 

 ary wood. Their strobili are cotnparatively well known and vary greatly in structural 

 details, presenting throughout a marked contrast to Equiseta, in the probable division 

 of their sporophylls into dorsal sterile, and ventral generally peltate sporangia-bearing 

 segments (Scott, Cheirostrobus, Phil, trans, roy. soc, 1897, B) . According to William- 

 son and Scott (Phil, trans, roy. soc, 1894, B. p. 864, 868, 890) their branches originated, 

 in contrast to those of Equisetum, above the nodes. From Weiss (Steinkohlen-Cala- 

 marien, Heft 2, p. 34), we learn that the roots of the Calamites were attached either at 

 the nodes or slightly to one side (he does not say, however, which side) . 



Most frequently calamitean remains occur as casts of the medullary cavities. These 

 casts represent accurately the inner configuration of the fibrovascular cylinder and are 

 consequently constricted at points corresponding to the nodal woody rings and channelled 

 along the course of the primitive bundles. As the primary rays between the primitive 

 bundles were bridged over more or less rapidly by the secondary wood, they appear 



