306 



LYCOPODIALES 



Scotland, has been compared by Penhallow 

 with Lycopodium Selago as regards the un- 

 differentiated shoot. 1 Without attaching too 

 much importance to the last example, it 

 appears certain that Lycopods, even of large 

 size, existed in very early times, in which 

 there was no clear differentiation of vege- 



the 

 the 



regions 



dates 



in fact, 

 back to 



tative and fertile 

 " Selago " condition 

 Primary Rocks. 



There can be no question of the Lyco- 

 podinous affinity of the fossils thus described 

 briefly in their general morphology : it 

 remains then to indicate where the nearest 

 correspondence is to be found between 

 them and living forms. They are plainly 

 related to the Ligulate Lycopodiales, and, 

 being of a radial type of shoot, and usually, 

 if not always heterosporous, the correspon- 

 dence is nearer to the radial species of 

 Selaginella : this suggests a comparison with 

 6". spiindosa, from which some interesting 

 points will emerge. In the first place, the 

 difference of size is to be discounted : how- 

 ever diverse the gigantic Lepidodendron may 

 seem from the minute S. spiintlosa, the com- 

 parison really relates to the relative position 

 and character of the parts composing the 

 plant-body. The parts which form the shoot 

 axis, foliage-leaf and sporophyll, the ligule, 

 and the sporangium are identical in both 

 as regards their relative positions, though 

 differing greatly in their number and dimen- 

 sions : in the dichotomous branching, and 

 in the relation of the resulting shoots to the 

 upright main axis they are alike : also in 

 the dependence of the whole plant for its 

 water-supply upon the base of the primary 

 axis. In fact, Si'lagi/iella spinulosa is like a 

 Lepidodendron in miniature, as regards the 

 scheme of its construction. The comparison 

 extends also to that curious knot which is 

 found at the base of the main axis in S. spinulosa : here the origin of the 

 roots is strictly localised : they appear endogenously on indeterminate 



' Cauaiian Record of Science, 1892, p. 8. 



Kic.. 154. 



Plenromoia Sternbergi, Axis, with 

 the lower part of the terminal strpbihis. 

 Two-thirds natural si/e. After P.ischof. 

 (From Kngler and Prantl.) 



