STEIL: POLYPODIUM IRIOIDES 273 
broaden out in some instances and form heart-shaped prothallia 
with rhizoids and antheridia. (TExT Fic. 1.) The anthero- 
zoids produced in the antheridia were seldom discharged in 
these instances and undoubtedly, disintegrated. One of the 
ring cells of the antheridium represented by Fic. 2 developed a 
secondary antheridium from which the. antherozoids had already 
escaped. 
In many instances, the sterile cells of an antheridium pro- 
duced secondary antheridia. Sometimes several of these were 
developed from the lid cell. Fic. 3 represents a lid cell (a) from 
which an antheridium (6) was produced. From the lid cell (d) 
of the larger secondary antheridium (c) a normal one (e) was de- 
veloped. Occasionally a ring cell produced one or more antheridia 
(FIGs. 4-6). 
The spermatogenous cells in antheridia whose sterile cells con- 
tained many chloroplasts, in several instances were observed to 
have disintegrated. Such antheridia were sometimes transformed 
into prothallia (Fics. 7-9). The cells of such antheridia usually 
increased in size and often divided into a number of cells (FG. 10). 
The great difference between normal and such abnormal antheridia 
is shown by Fic. 9. Many-celled prothallia produced from this 
kind of antheridium were found in the culture. 
Antheridia were also transformed into prothallia during their 
early course of development. It was obviously difficult to follow 
the development of these prothallia. An early stage in the 
transformation of an antheridium is shown by Fic. 11. The 
ring cells, in this instance, had divided to produce several cells. 
In some cases plastids were present in the central portion of the 
antheridium. These were, however, almost colorless, containing 
little chlorophyl. In this respect the young prothallia of this 
type differed from the ordinary secondary prothallia. The de- 
velopment of these prothallia could be followed only during their 
early stages, since at later stages of development they became 
similar in all respects to secondary prothallia produced in the 
culture. A most convincing instance of the transformation of an 
antheridium is represented by Fic. 12. The antherozoid cells 
can still be distinguished. The sterile cells by a number of di- 
