CALAMITES AND LYCOPODS 389 
OUTLINE OF LIFE HISTORY OF SELAGINELLA 
Sporophyte 
TT TT 
Microsporophyll Megasporophyll 
4- 4" 4' 4- 
Microsporangium Megasporangium 
4, < Reduction > J, 
Microspore Megaspore 
4- 4- 
Male gametophyte Female gametophytc 
4, 4, 
Antheridium Archegonium 
4 4 
Sperm Egg 
Oosperm 
44 
Embryo 
44 
Mature sporophyte 
360. Marks of Progress. With the introduction of 
heterospory we recognize a distinctly new feature of the 
sporophyte generation. Structural differentiations asso- 
ciated with difference in sex have hitherto been confined 
to the gametophytic generation, but now such distinctions 
appear for the first time in the sporophyte. This is a 
long step forward, and marks Selaginella as a more highly 
organized form than the lycopods, horsetails, and ferns. 
Other marks of progress are: 
1. The reduction of the vegetative tissue of the 
gametophytes (to only one cell in the case of the male 
gametophyte). 
2. The entire dependence of the gametophytes upon the 
sporophytes for nutrition. 
3. The retention of the female gametophyte, through- 
out its entire existence, almost entirely within the wall 
of the megaspore. 
