176 I>. H. Scott. 



higher plantsj is characterised bj' the production of true leaves (quite 

 witliout homology with phj^lloids), derived from the thallus b}' the 

 subordination of certain branches or branch-sj^stems. which acquired 

 dorsiventral organization and limited growth. 



Thus a fundamental distinction is drawn between Tmesipterids 

 and Lycopods on the one hand, and Ferns with all the rest of the 

 Vasculares on the other. We may venture to express Prof. Lignier's 

 arrangement in a tabular form, to compare with the provisional classi- 

 fication given on p. 147. 



f Tmesipterideae 

 Lycopodmeae { ■. ,. , 



•^ ^ i Lycopodiales 



Filicineae ■ 



Filicales 



Sphenophyllales \ 

 Equisetales / 



Articulatae 



( ycadofilices ) o i .. 



r, Spermophyta. 



Gymnospermeae ) "^ 



It would carry us too far to attempt any detailed criticism of 

 Prof. Lignier's views, which are worked out with great ingenuity. 

 I cannot accept the Tmesipterideae as a really primitive group, for 

 they seem to bear too evident marks of reduction from a more complex 

 type such as that of the Sphenophyllales. For reasons given above I 

 am also inclined to attribute some affinity with Sphenophj'llales to 

 the Lycopods, though I admit that this is a much more doubtful 

 point. On the other hand a relation between the Sphenophyllales 

 and primitive Filicineae may be conceded as probable, even though 

 all Prof. Lignier's arguments may not hold good.^) He has done 

 valuable service in calling attention to this probable relation, and 

 though the main divisions Lycopsida and Pteropsida have been adopted 

 here as convenient associations, I am inclined to extend the sj'nthetic 

 view of the Sphenophyllales so far as to admit that they retained 

 some characters, such as the venation of the leaves, common to the 

 Filicinean phylum. 



^) The double leaf-trace, on which Prof. Lignier lays stress, does not exist, so 

 far as I have found, in the most primitive known Ferns — the Botrj'opterideae, though 

 it of course appears in some of the Cycadofilices which may have an affinity to them. 

 See the followins: Section of this Article. 



