2o6 



MORPflOLOGY 



them a beaklike projection of the endosperm, a structure that char- 

 acterizes Ginkgo. No seeds have been found containing embryos ; and 



since the same fact is true of 

 the Cycadofilicales, it is evi- 

 dent that all the seed plants 

 of the Paleozoic shared this 

 fjeculiaritv. 



Conclusions. — A summary 

 of the cliaracters of Cordaitales 

 shoe's an interesting comliina- 

 tion. There are primitive 

 characters \\hich indicate con- 

 nection with the Cvcadofilicales 

 and the cycad line, such as the 

 large pith, the structure and 

 mesarch bundles of the leaf, 

 the structure of the ovule, and 

 the swimming s])erms. The 

 ad\'anced characters are the 

 loftv and branching hal)it, the 

 thick cylinder of secondary 

 wood, the form of the leaves, 

 and the compound ovulate 

 strobilus, all of which are char- 

 acters of the Coniferales. It 



Fig. 463. — Section of o^-uLite strobilus of 

 ont of the Cordaitalc-s, showing the large over- 

 lapping bracts, in the axils of two of which there 

 appear short branches bearing terminal ovule-^; 

 that to right also shows a bractlet. — After 

 Rf.n.^ui.t. 



Fig. 464. — Pollen grains of one 

 of the Cordaitales, showing the group 

 of internal cells that proljably belong 

 to the male gametophyte. — After 



REN.il'LT. 



seems evident, therefore, that the Cordaitales represent a second great 

 branch from the CycadohHcales stock, a branch which leads towards 

 the Coniferales: This branch seems to have sejjarated from the 

 Cycadofilicales long before the other branch which ends in the modern 

 Cycadales. 



