The Present Position of Palaeozoic Botany. 175 



ductive apparatus, the Lycopodiales differ widely from the Spheno- 

 phyllales. In these characters as well as in other respects the 

 Lycopods constitute a wonderfully homogeneous group, so neatly 

 rounded off as to give little hold for any hypothetical link with other 

 classes of plants. Sigillariopsis, with its double foliar bundle, departs 

 in some degree from the typical simplicity of structure, but there 

 is not the slightest reason for regarding this peculiarity as an 

 ancestral character. 



In certain respects the Psilotales tend to connect Sphenophyllales 

 with Lycopods. for while anatomy and morphology alike indicate a 

 nearer affinity with the former, some relation to the latter may no 

 doubt be traced in the anatomy and habit. In spite of this, the 

 Lycopodiales remain a very isolated class, and though some connection 

 with the ancient phylum represented by the Sphenophyllales appears 

 probable, the common stock must lie very far back. Whether the 

 simple relation between sporangium and sporophyll which characterizes 

 the Lycopod series is native or acquired, may be left an open question. 

 The analogy of the Psilotales rather suggests the latter alternative, 

 and all comparative morphology teaches how often progress consists 

 in simplification.^) 



The interpretation of the Lycopodiaceous sporangial apparatus 

 as the result of simplification has often been upheld, and has found 

 a supporter recently in Prof. Lignier, whose essay on the affinities 

 of Sphenophyllales and Equisetales (Lignier, 1903) is a wonderfully 

 suggestive contribution to the subject, though I cannot accept all his 

 conclusions. 



Prof. Lignier regards the Tmesipterideae (Psilotales) as the 

 nearest living representatives of his hypothetical "Pro-Lycopod", which 

 is supposed to have been the starting point of the vascular plants 

 when they first diverged from the still earlier "Pro-Hepatic" type. 

 The synangium of Psilotales is interpreted as a terminal spikelet 

 with concrescent sporangia and two fused "phylloids" at the base. 

 Prof. Lignier' s "phylloids" are a primitive form of leaf derived from 

 lamellate hairs (cf. amphigastria of Liverworts). The Lycopods, accord- 

 ing to him, are also phylloid-bearing plants, with a dichotomous 

 habit, but the spikelet of the Tmesipterids is here reduced to a 

 single axillary sporangium. Neither group has any but a very remote 

 connection with the Sphenophyllales, which Prof. Lignier derives 

 from an ancient Fern-stock. The whole Fern-series (leading up to the 



^) The ventral parenchymatous outgrowth which hears the sporangium in 

 Spencerites might conceivably be the last relic of a ventral sporangiophore. The 

 distal insertion of the sporangium, found in this genus, is very rare in Lycopods 

 and unknown among the recent representatives of the class. 



