The development of prothallia and antheridia from the sex organs 
of Polypodium irioides 
W. N. STEIL 
(WITH PLATE 4 AND FOUR TEXT FIGURES) 
INTRODUCTION 
The spores of Polypodium irioides Poir., from the culture of 
which were obtained the prothallia with the sex-organs to be 
described, were sown March 21, 1916. When the first prothallia 
had grown to maturity and a number had already produced sporo- 
phytes, the majority were removed for class use. Antheridia and 
archegonia were formed on the prothallia in large numbers. The - 
archegonia, as is usual in most ferns, were produced on the cushion 
back of the apical notch, and the antheridia in the majority of 
cases on the posterior portion among the rhizoids. They were 
also frequently formed along the margins of the prothallia. In 
a few instances antheridia were observed among the archegonia. 
On several occasions prothallia were examined with the micro- 
scope, but no abnormalities were observed in the development 
of the sex-organs. The smaller prothallia, as well as the larger 
ones, produced secondary prothallia in profusion. A modified 
Beyerinck’s solution* was several times applied to the Sphagnum 
on which the prothallia were grown. The illumination and the 
carbon dioxide and oxygen supply were sufficient for normal de- 
velopment of prothallia. The vigorous growth and the large 
size of the prothallia suggest that favorable conditions prevailed 
in the culture at least during its early history. 
The majority of the remaining prothallia were removed in 
October, 1918. Three sporophytes remained in the culture at 
this time and from these sporophytes sporophytic and aposporous 
* Moore, G. T. Methods for growing pure cultures of Algae. Jour. Appl. 
Microscopy 6: 2309-2314. 1903- 
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