1 14 Steil. — Apogamy in Nephr odium hirtipes , Hk. 
embryos now produced antheridia and archegonia, and sporophytes de- 
veloped only as a result of fertilization. The following summer the new 
projections again formed apogamous embryos. Heilbronn attributed the 
occurrence of apogamy to intense illumination, although he failed to obtain 
similar results in some other species placed under the same conditions. 
Some differences were observed between the two types of embryos of 
Cystopteris fragilis , but it was not determined whether the spores produced 
by the apogamously formed sporophytes would produce prothallia of the 
normal Cystopteris form, or those of the apogamous form which Heilbronn 
distinguished as Cystopteris forma polyapogama. Heilbronn also found 
apogamy in Aspidium aculeatum var. cruciato-polydactylum , Jones, and 
A. angular e forma grandidens, Moore. 
In several instances Miss Pace (1913) found on prothallia, probably of 
a species of Osmunda , sporangia similar to those described by Lang (1898). 
The prothallia had been grown for a long period, but were not subjected 
either to dryness or to strong illumination. She considered the prevention 
of fertilization by watering from below to be the cause of the formation 
of the apogamous embryos. 
Nagai (1914) obtained apogamous embryos of Asplenium nidus avis 
when the cultures were lacking in moisture, but he believed that high 
temperature and strong light may also be factors in inducing apogamy. 
Miss Allen (1911) studied the cytology of Aspidium falcatum , in which 
de Bary had discovered apogamy in 1878 . According to her description 
there is a fusion in pairs of the sixteen cells which ordinarily in the Poly- 
podiaceae function as the spore mother-cells. The eight cells produced by 
this fusion function as the spore mother-cells. By the nuclear fusion the 
double chromosome number is established, but the reduction division 
follows the fusion, so that the thirty-two spores which are finally formed 
contain the haploid number of chromosomes. 
In a preliminary note (Steil, 1915 b) I have reported a course in 
Nephr odium hirtipes similar to that described by Miss Allen. P'urther 
studies, as will be indicated in what follows, have led me to modify in 
certain respects the conclusions which I first formed regarding the cyto- 
logical basis of apogamy in this species. 
For the past six years I have grown the prothallia of a number of 
species of ferns for the purpose of determining the occurrence of apogamy 
and of investigating, so far as possible, the cytology of the apogamous 
forms. I have reported apogamy in Pellaea atropurpurea , L. (Steil, 1910), 
and later (Steil, 1915 a) in P. adiantoidis l J. Sm, Aspidium chrysoloba , A. 
tsussimense , and N ephrodium hirtipes , Hk. I have also found it to occur in 
Pellaea atropurpurea var. cristata, Trek, P. hast at a, L., Aspidium falcatum 
Rockford ian u m , A. falcatum Fortunei , A. falcatum caryotidium , Ptems 
sulcata , L., Pteris argyrea , Moore, P ter is Parkeri , and in a number of 
