ORGANIZATION OF VOLKMANNIA DAWSONI. 37 



search for its true affinities. It is the fruit either of As- 

 terophyllites or of Sphenophyllum ; and, judging from the 

 general aspect of its bractigerous disks, I am more dis- 

 posed to identify it with the former than with the latter. 

 But the important question now returns to us. What are 

 those verticillate plants which are not Calamitean ? The 

 first obvious fact is, that they possessed jointed stems. In 

 branched specimens of fructification in my cabinet, the ar- 

 ticulations of the central axis are very distinct, and about 

 an inch apart. The stems are flattened by pressure, and 

 exhibit slight indications of longitudinal ridges and fur- 

 rows, the origin of which I am unable to explain. They 

 are less regular and definite than those of Calamites. The 

 central axis of one of my examples of fruits is six inches 

 in length, giving off six verticils of spikes or strobili, each 

 of which is nearly two inches long ; and as I have every 

 reason for supposing that this specimen is only a portion 

 of the original structure, it seems more than probable that 

 the living axis, with its verticillate fructification, may have 

 approached a foot in length. The bractigerous verticils of 

 each strobilus are about the eighth of an inch apart, which 

 is rather more than in our specimen now described ; besides 

 which, the latter is broader than the specimens from the 

 shales, so that its spikes have been more compact than in 

 these examples. 



The verticillate arrangement of the leaves, and the arti- 

 culated character of the stems, forbid our associating these 

 plants either with Ferns or with Lycopodiacese. On the 

 other hand, the internal organization described in this 

 memoir show^ how different they have been from the true 

 Calamites. Yet the two features just referred to obvi- 

 ously indicate closer affinities with the latter genus than 

 with any other of the Carboniferous genera. I have arrived 

 at the conclusion that these plants constituted a distinct 

 family of Asterophyllitacese, whose place is near the Cala- 



