may give off branches into both the inner border of the sarcotesta and the nuceleus.
In a form called Cycadinocarpus angustodunen sis the archegonia are plainly present, hut em bryonic structures have never been observed in such seeds. They are scarcely separable from those of the quasi-ferns and greatly resemble the seeds of modern cycads. The seeds of the cycadeoids, owing to reduction, present a far less visible similarity.
The Cordaitales derive a unique significance from their age and primitive characters, so manifestly important in our conception of the manner and course of plant evolution. Botan fists have been inclined to believe that the Cor daitalean and Cycadalean groups had a corimon filicalean ancestry, and that from the Cordaitales have been derived the Ginkgoales, the Co!lifer ales and probably the Gnetales. Some would ------ --- ------- go further and place the Cordaitales in a posi tion ancestral to angiosperms as well. Opinion is about equally divided between a Cordaitalean and an Equisetalean derivation of Araucaria. Recent investigation calls these theories of descent more in question. It is now recognized that fossil types are seldom the true antecedents of later forms. Most fossil plants represent terminal climax constituents in the floras of the past; while the extent of homoplasy and parallelism yet remains to be measured. Cer
tainly increasing knowledge of the Cordaiteans will show them to be more varied than as yet conceived, and in any case their discovery must be regarded as one of the great triumphs of palmobotany.
Dawson, 'Fossil Plants of the Devonian and Upper Silurian Formations of Canada' (1871) ; Dawson, 'Acadian Geol Grand 'Eury, (Fiore Carbonifere de la Loire et du Centre de la France,' (in Mem. Inst. de France, Tome XXIV, 1877) ; Lesque reux, 'Second Geological Survey of Penn sylvania) (Report P, 1880) ; Brongniart, 'Recherches sur les graines fossiles silicifiees> i (1881 ; Renault, 'Course de botani9ue fossile' (1881 ; Scott, 'Studies in Fossil Botany) (1903 ; Stopes, "On Leaves of Cordaites) (in New Phytologist, Vol. II, Nos. 4, 5, 1903); Zalessky, 'Dadoxylon Tchihatcheffi G6eppert Sp' (in $Memoires Comite Geologique' New Ser. Liv. 68, Petrograd 1911) ; Elkins and Wieland, 'Cordaitean Wood from the Indiana Black Shale> (in American Journal of Science, Vol. XXXVIII, 1914) ; Scott and Jeffrey, On Fossil Plants, showing structure from the base of the Waverley Shale of Kentucky) (1914) ; Wieland, 'American Fossil Cycads' (Vol. II, 1916).