ORGANIZATION OF VOLKMANNIA DAWSONI. 39 



bractigerous disks, whose functions are merely protective. 

 The latter gives off a bractigerous disk from each node, as 

 is also the case with my previously described Calamitean 

 strobilus ; but the relations which the sporangiophores 

 bear to the sporangia are very different in the example 

 nnder consideration from what obtains in either of these 

 other cases. The sporangiophores spring in great num- 

 bers from the entire upper surface of the bractigerous 

 disk, though not from its peripheral bracts, the sporangia 

 themselves being loosely aggregated; in the Calamitean 

 type each sporangiophore ascending from the bractigerous 

 disk sustained three or four sporangia closely clustered 

 around it, the entire mass of the fruit being rendered 

 very compact through the intense mutual pressure of its 

 sporangia. 



Two fruits so different in the details of their structure 

 as Volkmannia Binneyii and the subject of this memoir 

 must, as I have already observed, belong to distinct gen- 

 era ; consequently it is desirable to separate them. This 

 can readily be done by accepting Professor Schimper's ge- 

 neric name, calling the one fruit Calamostachys Binneyana, 

 and retaining the other, for the present, in the provisional 

 genus Volkmannia. But as the specific features of the 

 latter are very distinctive, and as I cannot identify it speci- 

 fically with those forms of which the external aspect alone 

 has been so often described, I propose to distinguish it by 

 the name of Volkmannia Daivsoni, associating with it the 

 name of the eminent geologist w T ho has contributed so 

 much to our knowledge of Canadian palseophytology. 



I may observe in conclusion that, though Calamostachys 

 Binneyana exhibits features which mark strongly the ge- 

 neric differences between it and Volkmannia Dawsoni, the 

 organization of its central axis brings it much nearer to 

 the latter plant than to the Calamites, with which Mr. 

 Carruthers and others have associated it. 



