98 BOTANICAL GAZETTE [JANUARY 
prothallia of the Polypodiaceae and the Cyatheaceae because of 
the differences in the antheridia and in the types of hairs. 
From 2 to 15 cultures were made of all the species studied, the 
cultures running from 5 to 15 months. Various media were used: 
several different mixtures of soil; black peat, with and without 
Knop’s solution; and porous clay crock standing in Knop’s solu- 
tion. Some of the cultures were raised in a laboratory where they 
received no direct sunlight except late in the afternoon; others were 
raised in a greenhouse where they received sunlight except for a 
few hours at midday. 
The few cases of apogamy found occurred in the genera Dick- 
sonia and Cyathea. They were found in cultures on peat raised 
in the greenhouse in the winter of 1915-1916. I am indebted to 
Professor A. VINCENT OsmuN of the Massachusetts Agricultural 
College for data on the weather of that winter and the 5 years pre- 
ceding. While the total number of hours of sunlight for the winter 
of 1915-1916 was a little below the average, the number of days in 
which there was snow on the ground was considerably above the 
average, so that the greenhouse cultures of that winter probably 
received more light than any other set of cultures. Lane (8) 
regards intense light and probably high temperature as important 
factors in the development of apogamous structures. SCHLUM- 
BERGER (10) found that in the case of Woodsia ilvensis the pro- 
duction of the cylindrical process was caused by such unfavorable 
conditions as weak light and dryness. HErtLBRon (4) did not find 
dryness to be a factor and suggests that summer cultures are more 
likely to become apogamous than winter cultures, but his experi- 
ments with different qualities and intensities of light in moist cul- 
tures at a high temperature gave negative results. Mme. WORONIN 
is inclined to regard dryness as the cause of apogamy in the forms 
which she studied, as in these cases it cannot be attributed to intense 
light. This explanation is criticized by Isasuro-Nacat (6), who 
found that in the case of Asplenium Nidus dryness was not a factor 
and that the cause seemed to be either an unfavorable culture con- 
dition or an unknown physiological condition. The cases discussed | 
in the present paper are too few in number to be of much signifi- 
cance. It cannot be a question of dryness, as the cultures were on 
