98  E?tTER: POLYEMBRYONY IN POLYPODIACEOUS FERNS 
Professor Henry F. A. Meier of Syracuse University, Syracuse, 
New York.* Spores of Onoclea sensibilis were collected by the 
writer in the vicinity of Indiana University, while those of 
Dryopteris mollis and Pteris longifolia were secured from plants 
grown in the departmental greenhouse. 
The same methods were used for all the species, excepting 
the prothallia of Pteris longifolia, which were transplanted with- 
out being examined under the microscope. 
The spores were sown on rich soil from the woods. The soil 
was sterilized at approximately 100° F. in earthen saucers, in a 
steam sterilizer, for a period of two to six hours, permitted to 
cool, and surfaced with a rather thick sowing of spores. The 
cultures were kept on tables under ventilated bell-jars in the 
greenhouse, where ordinary greenhouse conditions existed. 
They were sub-irrigated with distilled water from time to time 
as needed. The first green of the surface appeared in from five 
to eight days. 
Archegonial prothallia were selected for experimental pur- 
poses when they became 3-5 mm. across the lobes. All pro- 
thallia were removed from cultures and cleaned sufficiently in 
distilled water to permit of a good examination. They were 
then transferred to a drop of distilled water on a slide and care- 
fully examined. If archegonia were open and no spermatozoids 
present a few male prothallia were placed near the sinus and the 
whole covered with a cover glass. The sperms were followed to 
the egg-cells under the microscope. The gametophytes were 
then left on the slides with cover glass removed, or placed in a 
ventilated moist chamber for about thirty minutes. On account 
of class room pressure some of them were permitted to remain 
in this condition for three or four hours. Results secured in both 
cases were the same. All archegonial prothallia were then very 
carefully transplanted about an inch apart on moist soil, care 
being taken that the specimens were not too wet for twenty-four 
hours. The soil and air were just moist enough to keep the 
prothallia in good condition. After periods of from five to 
twenty-six days the gametophytes were harvested for study. 
*In all probability the spores used were American in origin and would 
therefore represent M. nodulosa (Michx.) Fernald (Pteretis nodulosa Nieuwl.), 
rather than the true M. Struthiopteris of Europe (see Fernald, Rhodora 17: 
164. 1915). 
