1900] CURRENT LITERATURE 353 
aebut divergent lines from an ancient stock represented by the Sphenophyl- 
les, Professor Scott regards the Sphenophyllales as worthy to stand asa gym- 
| Msperm group of primary rank. He would include in it not only Sphenophyl- 
lm and its acknowledged associates, but Cheirostrobus as well, a genus 
which strikingly combines the characters of Equisetales and Lycopodiales. 
_ Of course the Filicales are fully considered, a group of enormous 
Uutiquity, having held its own since the Silurian, and whose habit was so 
 fredominant during the Paleozoic that many plants have been included with 
them whose real affinities are elsewhere. In general, Professor Bower's 
| Souping of Filicales into the Simplices, Gradatae, and Mixtae is shown to 
lave an historical basis. 
One of the most interesting sections of the book is that devoted to a con- 
 Sileration of the Cycadofilices, a provisional Paleozoic group made to contain 
- fms which combine the characters of Filicales and Cycadales, and most of 
; them first described as ferns. The representative genera are Lygino- 
- tendron, Heterangium, and Medullosa, whose habits and anatomical features 
_ % strikingly intermediate, but whose spore-bearing members are unfor- 
: ‘mately unknown, It is evident, however, that in them we have forms 
Ene confirm the conclusion that cycads have been derived from 
Aswas to be expected, the dominant gymnosperm group of the Paleozoic, 
: ee. is set apart as of primary rank, and, associated with the Cyca- 
3 “gg seems to furnish the background for later gymnosperm develop- 
