] ORIENTATION OF THE PLANT EGG 323 
- eptosporangiate ferns; and the zzverted, characteristic of Lyco- 
- podinee and Spermatophyta. 
4, The origin of the primitive type is in adaptation to the 
- geripheral position of the archegones and to the plane of the sub- 
‘stratum; the origin of the semi-inverted type is in adaptation to 
trived archegonial positions and resistance of prothallial areas, 
interfering with the direct normal growth of the embryo; the 
omgin of the inverted type is in adaptation to repeated arche- 
gonial displacements and nutritive qualities of prothallial areas 
jacent. 
_ §. The phylogenetic sequences derived from such an ecolog- 
- ‘al investigation of embryos do not materially differ from those 
- tttived by a study of pure morphology. 
UNIVERSITY OF MINNESOTA. 
