102 STEIL: SOME NEW CASES OF APOGAMY IN FERNS 
In one of the cultures of Pteris sulcata, conical and nearly 
spherical projections were observed in the lobes of the prothallia. 
Some of these prothallia were transferred to another culture, and 
the growth of the projections was followed in both cultures. The 
projections produced either secondary prothallia or apogamous 
embryos. The former were often cylindrical at the point of origin, 
but in other respects they resembled the ordinary prothallia of 
Pieris sulcata. As many as six embryos were observed on the 
lobes of a single prothallium. In most instances these were nor- 
mal, producing both roots and leaves. 
By cultural conditions secondary prothallia have been pro- 
duced from the primary prothallia of many of the apogamous 
species. These prothallia also form embryos apogamously. 
DeBary (1878) reported that such prothallia of Pteris cretica 
albo-lineata seldom produced embryos. However, in my cultures 
of the same species, the secondary prothallia usually produced 
embryos of apogamous origin. Secondary prothallia of Pellaea 
atropurpurea, Aspidium hirtipes, Pteris sulcata, Pteris argyraea, 
and Pteris cretica albo-lineata Alexander frequently produce apoga- 
mous embryos. 
THE INFLUENCE OF WEAK ILLUMINATION ON THE DEVELOPMENT 
OF THE- PROTHALLIA AND OF THE APOGAMOUS EMBRYOS 
- When the prothallia of the apogamous species were placed 
under the influence of weak light, the same results were obtained 
as with the non-apogamous ferns. Filaments were formed from 
the margin and both surfaces of the prothallia (PLATE 5, FIG. 21), 
and these under the normal conditions of illumination in the war- 
dian case became, independent prothallia, which in nearly all 
instances formed also apogamous embryos. When the prothallia 
were maintained in weak light, they remained simple or branched 
filaments, producing neither sex-organs nor embryos (PLATE 5, 
FIG. 18). Under somewhat more favorable conditions of illumi- 
nation, ribbon-like plates were produced, which frequently bore 
numerous antheridia and _ occasionally apogamous embryos. 
When the illumination was slightly less than that in the greenhouse, 
the prothallia became lobed (PLATE 5, FIGS. 14 and 15). In the 
new apical regions which were formed embryos also made their 
appearance (PLATE 5, FIG. 17). 
