94 STEIL: SOME NEW CASES OF APOGAMY IN FERNS 
spores were collected from these. Spores from a still larger 
number of species were obtained through the kindness of the fol- 
lowing persons: Dr. A. B. Stout, New York Botanical Garden; 
Dr. R. C. Benedict, Brooklyn Botanic Garden; Dr. G. T. Moore, 
Missouri Botanical Garden; Dr. E. B. Copeland, Los Banos, 
Philippine Islands; Mr. F. C. Greene, Rollo, Missouri; and Rev. 
George Moxley, Los Angeles, California. To these gentlemen the 
writer wishes to express his sincerest thanks, for in no small 
measure they contributed to the investigation. 
The spores were generally sown on the surface of a nutrient 
solution or on sphagnum. The latter was placed in a Stender 
dish and saturated with a nutrient solution. Before sowing the 
spores, the medium was thoroughly sterilized. Other media, such 
as nutrient agar, peat clay and loam, were also used, but none 
of these proved as satisfactory for the cultural work as the sphag- 
num. The Stender dishes were placed under bell-jars in a Wardian 
case in the university greenhouse. The jars were tilted on edge, 
so that the prothallia were provided with a sufficient supply of 
oxygen and carbon dioxid. The temperature of the Wardian case 
varied from 65° F. in winter to about 110° F. in summer. The 
prothallia were protected from too intense illumination by shading. 
The light was very favorable for the growth of fern prothallia 
since, when they were not crowded in the cultures, they became 
heart-shaped. The moisture supply was always sufficient for 
fertilization to occur in the non-apogamous species grown at the 
same time under precisely the same cultural conditions. 
In a large number of species in which fertilization is known to 
occur, including Pteris aquilina L., P. serrulata L., Osmunda re- 
galis L., O. Claytoniana L., O. cinnamomea L., and Adiantum 
pedatum L., sex organs were produced under the conditions just 
described, and embryos were formed only as a result of the union 
of the gametes. 
The prothallia of Nephrodium molle Desv. and Asplenium 
nidus L., in which Yamanouchi (1908) and Nagai (1914) respec- 
tively induced apogamy, were grown under the same conditions, 
_ but while embryos were produced in large numbers, none were 
formed apogamously. 
The spores of some of the apogamous species were sown on soil 
