Steil. — Apogamy in N ephrodium hirtipes , Hk. 1 1 5 
varieties of Ptcris ere tic a (Steil, 1918). Anthcridia are produced on the 
prothallia of all the species in which I have observed the development of 
apogamous embryos. Archegonia are, however, developed in only a few of 
these species. Cytological studies of the apogamous ferns have already 
been begun, and in several species the history of the sporogenous cells 
appears to be similar to that herein described for N ephrodium hirtipes. 
In all the apogamous ferns which have so far been investigated, 
antheridia appear to be developed except in Trichomanes alatum and 
T. Kraussii . In these two species antheridia never develop to maturity. 
In numerous cultures of the prothallia of Pellaea atropurpurea, L., anther- 
idia were found by the writer, but under certain cultural conditions they 
frequently appear in large numbers. I 11 a number of species archegonia are 
never produced, in a few they abort, and in still others they are apparently 
developed to maturity. Whether fertilization occurs in the latter cases, as 
reported by Heim (1896) and Heilbronn (1910) for some of the apogamous 
species, is a question that must be left for further investigation. 
Materials and Methods. 
The reader is referred to my preliminary note on N ephrodium hirtipes 
(1915 b) for a brief description of the cultural conditions under which the 
prothallia were grown. In the many cultures which have been made since 
the discovery of apogamy in this species, no important differences have been 
observed in the development of the prothallia or in that of the apogamously 
produced embryos. 
The spores of N ephrodium hirtipes from which the prothallia were 
grown were collected from plants grown in the university greenhouse. Five 
of these plants were obtained from the first culture of the prothallia made 
December 14 , 1913 . The others were obtained from different sources. 
The rate of growth and the size of the prothallia were affected by the 
strength of the nutrient solution, the temperature, the moisture, and the 
illumination. Too intense illumination was avoided by shading. The 
moisture supply was sufficient to allow fertilization to occur in all of the 
numerous non-apogamous species which have been grown under the same 
conditions as TV ephrodium hirtipes. The temperature of the Wardian case 
in which the prothallia were grown varied from 70 ° F. in winter to about 
1 io° F. in the hottest days of summer. While a o-x per cent. Knop’s 
solution was generally used for the prothallia grown on sphagnum, various 
strengths of this solution were used and the spores were sown also on the 
surface of the liquid medium. Beyerinck’s solution as modified by Moore 
(1903) also proved very satisfactory. By tilting the bell-jar^ which were 
placed over the uncovered Stender dishes with the growing prothallia, an 
abundant supply of oxygen and carbon dioxide was provided. 
