264 STUDIES IN FOSSIL BOTANY 



times the diameter of the microspores ( 5 00-6 5 o //.). Both 

 kinds of spore have an equatorial ring or collar. The 

 chief differences from Selaginella are in the numerous 

 series of sporophylls, as compared with the tetrastichous 

 vegetative leaves, and the relatively large number of 

 megaspores in the sporangium, while in Selaginella 

 they do not exceed four. M. Halle, in his recent paper 

 on fossil herbaceous Lycopods, 1 describes a Coal- 

 measure species (S. elongatus (Goldenberg)), likewise 

 with dimorphic foliage, in which the sporangia appear 

 to arise in the axils of ordinary leaves, no strobilus 

 being differentiated. Microspores were not observed, 

 but some of the sporangia were found to contain from 

 twenty to thirty spores, about 450 /j, in diameter, so there 

 can be no doubt that the species was heterosporous ; 

 the absence of a specialised strobilus is interesting, as 

 no such case is known among recent Selaginellas. 

 Another species of similar age, investigated by M. 

 Halle, 5. primaevus (Goldenberg), is remarkable for its 

 close agreement with the recent genus. In this case 

 definite terminal strobili are differentiated ; the sporo- 

 phylls as well as the leaves of the smaller branches are 

 uniform and spirally arranged (as in Selaginella spinosa), 

 though it is possible that dimorphism may have 

 occurred in the main stems. The most interesting 

 point is that each megasporangium contained four 

 tetrahedrally arranged megaspores (400-500 fi in 

 diameter), just as in the living Selaginellas. Thus the 

 Selaginella type, if not the actual genus, is shown to 

 date from Palaeozoic times. The species 6". Suissei and 



1 Halle, " Einige krautartige Lycopodiaceen Palaozoischen und Meso- 

 zoischen Alters," Arkiv for Botanik, Stockholm, 1907. 



