192 Thompson.—Different Types of Angiospermic Vessels. 
Literature cited. 
1 . Bliss, Mary C. : The Vessel in Seed Plants. Bot. Gaz., lxxi. 314-26, 1921. 
2 . Brown, F. B. H. : Scalariform Pitting a Primitive Feature in Angiospermous Secondary Wood 
Science, N. S., xlviii. 16-18, 1918. 
3 . MacDuffie, R. C.: Vessels of the Gnetalean Type in Angiosperms. Bot. Gaz., lxxi. 438-45,192 1 
4 . Solereder, Hans : Systematic Anatomy of the Dicotyledons. Oxford : Clarendon Press, 1908. 
5 . Thompson, W. P. : Independent Evolution of Vessels in Gnetales and Angiosperms. Bot. Gaz. 
lxv. 83-90, 1918. 
