30 Brown: APOGAMY IN PHEGOPTERIS POLYPODIOIDES 
under light conditions which not only proved sufficient for 
the production of normal sporophytes but which failed to 
retard their development in those cultures of the full solutions 
which were renewed frequently. (2) In cases where apogamous 
prothallia from a nutrient solution with one of the essential 
elements omitted were transferred to a fresh full nutrient 
solution, thereby permitting the vitality of the prothallia to 
be renewed, no more apogamous outgrowths or sporophytes 
_ were formed, although the cultures were kept under the same 
light and temperature conditions. In some cases normal sporo- 
phytes developed. The formation of these normal sporophytes 
ceased as soon as the new solution was exhausted and the vitality 
of the prothallia thereby lowered. (3) Some of the prothallia 
which had developed upon a full nutrient solution, when removed 
to the physiological action of an incomplete solution. The 
while others are more tolerant. (4) Apogamous prothallia 
occurred frequently in uncrowded regions of the cultures where 
light conditions were very good, while on the other hand in the 
cultures of the full solutions normal sporophytes developed in 
the most crowded regions where the light condition was the 
poorest. 
The factor of temperature can not be considered as the 
controlling factor in apogamy in Phegopteris polypodioides. 
The prothallia in all cultures, both those which produced 
normal sporophytes when the food supply was sufficient and 
those which produced apogamous ones when the food supply 
was insufficient, were kept under the same temperature condi- 
tions. : 
