IN PTERIDOPHYTES 217 
assume a cylindrical symmetry. On this hypothesis the dorsiventral was 
the prior state for both the sporophyte and the gametophyte, and the 
radial the derivative. The author himself states that this “ prohepatic” 
type, from which the two generations were evolved, is still wholly hypo- 
thetical. As regards the sporophyte, since the embryology gives no 
countenance to an originally dorsiventral ‘prohepatic” state, while 
instances are common of the impress of dorsiventrality upon parts of it 
originally radial, the theory of Lignier cannot be upheld. It may apply 
for the gametophyte, but that has nothing to do with our present dis- 
cussion. It seems the unavoidable conclusion from the facts that the 
primitive symmetry of the sporophyte was radial. 
