BRowN: APOGAMY IN PHEGOPTERIS. POLYPODIOIDES 31 
Poor soil as a factor in causing apogamy would be operative 
either through the absence of the elemeats necessary for develop- 
ment or the presence of those elements in such a form as not to 
be available for the use of the prothallia. In either case it 
would be a lack of sufficient nourishment which would be the 
stimulus to apogamy. The results secured on poor soil would 
compare with those obtained in Phegopteris polypodioides where 
the apogamous outgrowths and sporophytes were due to in- 
sufficient nourishment. The proof for this is the fact that no 
cases of apogamy were observed in cultures of the full nutrient 
solution when it was renewed frequently; or, in other words, 
when a sufficient food supply was available. Also, apogamous 
outgrowths and sporophytes ceased to develop, and in some 
cases normal sporophytes were formed, when the nutrient 
solutions were renewed in the cultures, although other factors 
remained the same. Still further evidence is the fact that 
frequently the apogamous outgrowths showed a reversion from 
a more or less complex structure, several cells in thickness, 
bearing tracheids to a simple prothallus-like body only one cell 
in thickness and branched, indicating a still greater lowering 
of the vitality, which was doubtless due to an insufficient food 
supply. 
Prantl’s (’81) work on the nutrition of ferns, Klebs’s (’93) 
valuable studies on the physiology of reproduction, and the 
work of others have demonstrated that an intimate connection 
exists between nutrition and growth, and between growth and 
reproduction. Since both growth and reproduction are depend- 
ent upon nutrition, it would seem as if nutrition was the 
most important if not the controlling factor in causing apogamy. 
Farmer and Digby (’07), Winkler (’08), Allen (’11), and others 
are of the opinion that the morphological characters of the game- 
tophyte and sporophyte are not determined by the chromosome 
numbers as such. It would seem as if the morphological features 
were determined to a large extent by physiological characteristics, 
and that the difference between the gametophytic and sporo- 
phytic tissue was not a marked one physiologically. Apogamy 
seems to be due in all cases to a lowering of the vitality of the 
prothallia to such an extent that normal sporophytes can not 
be formed. This may be brought about by one or more factors 
working separately or together. Therefore, apogamy may be 
