PRESENT POSITION OF PALEOZOIC BOTANY—SCOTT. 889 
certain Marattiacee; but each sporangium has a multiseriate annulus 
closely resembling that of Zygopteris. 
Other genera which on the characters of stem structure may be 
referred to the Botryopteridee are Anachoropteris, Asterochlena, 
and Tubicaulis. The earliest of these (Asterochlena) dates from the 
Upper Devonian. 
The new genus, Botrychioxylon, has the elements of its outer zone 
radially arranged, constituting, to all appearance, a secondary tissue, 
just as is the case in Botrychium among recent Ferns. Anatomically 
Botrychioxylon shows a relation to Zygopteris, like that of Botry- 
chium to Ophioglossum. On the characters of the sporophylls and 
sporangia the nearest comparison of Botrychioxylon appears to 
lie with the Osmundacez and Ophioglossacex, while the anatomy and 
mode of branching of Zygopteris shows the closest analogies with the 
Hymenophyllacee. The group has been considered as a synthetic 
Fic. 7.—Pteridotheca Williamsoni. Two sporangia, to show the annuli. From a photo- 
graph by Mr. Boodle. X about 70. 
one, not improbably representing the stock from which some at least 
of the families of recent Ferns were derived. Mr. Arber regards the 
Botryopteridee as but one important family of the ancient race of 
Ferns to which he gives the general name of Primofilices, and con- 
siders it more than probable that this race gave rise to the Leptospo- 
rangiate. The relation of the Botryopteridex, or rather of the Pri- 
mofilices in general, to the Pteridosperms is an important question to 
which we shall return below. 
Other types which we may safely assign provisionally to the group 
Primofilices include Stauropteris and certain petrified sporangia 
which possess an annulus or other characters indicating Filicinean 
affinity, and which I have therefore designated Pteridotheca. The 
sporangia of Pteridotheca Williamsoni are borne in sori on the in- 
curved margins of a much-divided leaf, apparently of Sphenopteroid 
form. They are sessile, with a multicellular base, and ellipsoidal or 
nearly spherical in form, though their sides are often flattened by 
