from the Lanarkshire Coal-field. 475 



nor are the spores provided with elaters, as in Equisetum *. 

 But in the order Lycopodiacea? some members are hetero- 

 sporous and others isosporous. For example, Lycopodium 

 has only one kind of spore (isosporous), while Selaginella has 

 both microspores and macrospores {heterosporous) . It may, 

 perhaps, be found then that, although some of the cones which 

 are supposed to belong to Calamites show a heterosporous 

 condition, this may not be of sufficient importance to exclude 

 them from the Equisetacese, where the spores are isosjjorous. 

 It is also most probable that the genus Calamites, when its 

 fructification is more fully examined, will require to be sepa- 

 rated into many genera ; and in this light the genus Calamites, 

 as Weiss points out, can only be regarded as of a most 

 provisional nature. 



The roots of Calamites are those fossils to which Lindley 

 and Hutton applied the name of Pinnularia. 



From our present standpoint of knowledge Weiss proposes 

 to divide the genus Calamites into the four following 

 groups : — 



Calamites, Suckow (provisional genus). 



Division A. Furrows on stems alternating at the 

 nodes or joints. 



Group I. Calamitina, Weiss. 



Branch-scars occurring periodically, the nodes bearing scars 

 being separated from each other by a certain number of joints 

 which do not bear branches. In most cases there is a distinct 

 increase or decrease in the length of the joints which connect 

 the branch-bearing nodes. 



Group II. Ev -calamites, Weiss. 



Branch-scars occurring on every joint. The joints are of 

 the same length or of irregularly different lengths. 



Group III. Stylocalamites, Weiss. 



Branch-scars occurring without definite order, subordinate ; 

 often long stretches of the stem occur on which the branch- 

 scars are entirely absent. The joints are of equal length or 

 irregularly different. 



* See also Dr. Williamson's papers on the structure of Calamites pub- 

 lished at various dates in the ' Philosophical Transactions.' 



