Volume 3, first published in 1917, contains systematic descriptions of fossil seed plants.
28. Cycadales (recent); 29. Pteridospermeae (continued from volume 2); 30. Medulloseae, Steloxyleae; 31. Pteridospermeae (foliage and seeds); 32. Cycadofilices; 33. Cordaitales; 34. Cordaitales (continued); 35. Palaeozoic Gymnospermous seeds; 36. Cycadophyta (fossil); 37. Cycadophyta (fossil) (continued); 38. Cycadophyta; 39. Cycadophyta (fronds); Bibliography; Index.