322 LYCOPODIALES 



is doubtful what is the evolutionary relation between the distal and the 

 basal insertion of the sporangium upon the sporophyll ; whether the one 

 or the other is the more primitive in the Lycopodiales must be left for the 

 present open, but it is evident that such differences as these are of degree 

 only, in a type which is constant as regards the numerical relation of the 

 sporangia to the sporophylls, and in the coincidence of the median planes 

 of both of those parts. There seems little reason to hold that these 

 peculiarities of Spencerites are archaic relatively to those of the ordinary 

 Lycopodinous type. Comparison does not make it necessary, nor even 

 probable, while stratigraphically the ordinary Lycopod type is quite as 

 early as Spencerites. 



The same relation of sporangium to sporophyll as is seen in the 

 living Lycopbds is maintained in the Lepidodendroid cones, which are 



FIG. 168. 



Lepidpstrobus Brownii. A radial section traversing the axis, a sporophyll, and a 

 sporangium. In the latter numerous spores are seen partially filling it, while sterile 

 processes project upwards into the cavity. (From Sowerby's drawing.) 



known in many cases to bear ligules, and to be heterosporous, thus 

 corresponding more especially to the ligulate series of the Lycopodiales; 

 but this may possibly not be the case for all of them. An examination 

 of the details of the sporangium will naturally be best carried out in the 

 best preserved specimens, though these may not be generally typical of 

 all others. Lepidostrobus Brownii, Schpr., is probably the best preserved 

 of Lepidodendroid cones, and it will therefore be taken first. The large 

 silicified specimen in the British Museum was first described by Robert 

 Brown, with drawings by Sowerby. 1 The original specimen was about two 

 inches in length, and of about the same diameter : it was evidently only 

 the upper half of a strobilus, as the internal structure, which is preserved 

 with singularly little distortion, shows to be the case. It has been cut 

 into transverse, radial and tangential sections, and consequently a very 

 adequate knowledge of the details can be obtained. The central axis 



1 Linn. Trans., vol. xx. See also Misc. Bot. Works of Robert Brown, vol. i., p. 583. 



