CALAMAKIEAE. 331 



factions, Calamostachys tuberculata, Weiss, is known only in the form of 

 impressions, which however show the organisation since the sterile whorls 

 are but slightly closed. It is a well-known spike already figured by Stern- 

 berg l as Bruckmannia tuberculata, and has been found not unfrequently in 

 the Carboniferous schists of various deposits, at Ilmenau, at Saarbriicken, 

 at Zwickau, and at Schlan in Bohemia. According to Weiss two forms of 

 organisation occur in Calamostachys tuberculata simultaneously on different 

 spikes of the same plant. First there are the ordinary sporangiophores 

 placed in the middle of the member, but each with only two sporangia, one 

 above and the other below. Besides these there are sporangiophores of a 

 different character in the form of stout prickles like those of the rose and 

 bent downwards, which have a single sporangium only in the angle, and are 

 inserted immediately beneath a sterile whorl. This whorl has many mem- 

 bers (twenty to thirty according to Weiss), and consists of upward-curved 

 linear leaves. Schenk 2 has since brought forward some important objections 

 to this account. He shows that the two types of organisation assumed by 

 Weiss are sometimes found even on the same spike, and he concludes from 

 this that they only represent different modes of preservation of organs 

 originally alike. He says 3 : 'What I dispute is, that two forms of sporo- 

 phylls running a different course of development occur normally in the 

 same species, for the history of development in extinct plants is subject to 

 no other laws than those which govern it in living forms.' This, apart from 

 the possibility which exists of a different development of the leaves bearing 

 macrosporangia and microsporangia, is no doubt true. Then to explain 

 the origin of the prickle-like sporangiophores, Schenk supposes that the 

 upper sporangium had its margin forced by the pressure beyond the sporan- 

 giophore, and so the two became combined in a common impression. 

 Another similar explanation, which appears to myself and Stur 4 to be still 

 more satisfactory, and which is quite in keeping with Renault's statements 

 concerning Calamostachys Grand' Euryi, is that the prickle-like sporangio- 

 phore is formed of the stalk of the sporophyll and the radial tissue-plate, 

 which connects the latter with the whorl above and which is here torn 

 away to the base. It is true that this mode of explanation presupposes 

 that there were not two or one but four sporangia present as usual, and 

 that only two of these are seen in the impression. The upper one of the 

 two, if still present, must also be flattened together with the vertical wing 

 of the sporangiophore into a homogeneous plate of coal. In this way the 

 structure of Calamostachys tuberculata may be reconciled with that of C. 

 Grand' Euryi. There remains only the peculiarity of the varying length of 

 the internodes, for the whorls of sporophylls are undoubtedly placed far above 



1 Steinberg, Graf von (1), Heft 1-4, p. 29 ; t. 21, f. 4. 2 Schenk (2), p. 231, &c., and t. 36. 



3 Schenk (2), p. 232. * Stur (5), p. 146. 



