1910] TWPSS—PROTHALLIA OF ANEIMIA AND LYGODIUM 175 
heart-shaped (figs. 19-22). GOEBEL (11, p. 204) has called atten- 
tion to the fact that for a time the wings of such a prothallium are not 
of the same size. This unequal lobing is commonly the case with 
Lygodium circinatum, as may be seen from fig. 22. The apical cell, 
however, has clearly a terminal position (figs. 20-22), and the inequal- 
ity of lobing seems in this case to come from the faster growth on one 
side than on the other. Occasionally the two wings seem to develop 
equally, and in the end they are of equal size in both cases. As 
BAUKE reports, the apical cell persists for a relatively long time, but 
finally gives place to several initials. 
SEX ORGANS 
Antheridia appear in about three weeks, before the apical cell 
of the prothallium has been succeeded by the group of initials. Any 
cell of the prothallium may grow out into a papilla which is cut off 
to form an antheridium. These usually appear on the lower surface, 
but are found now and then on the upper surface as well. The first 
wall of the antheridium is often flat (fig. 23), as KNy (14) reports, 
but may be so concave as to touch the basal wall (fig. 24). There 
seems to be nothing here, at least in the ordinary forms, that could 
be called peculiar to the gametophyte of this family. Occasionally, 
however, more of a stalk is formed in a manner resembling the anther- 
idia of the Osmundaceae (fig. 25). One such case is reported by 
HEI (12). 
The formation of a dome-shaped wall and the cutting off of a 
cover cell follow, and the central cell divides to form a large number of 
spermatogenous cells; in Lygodium 128 sperms seem to be the 
characteristic number. 
Within six weeks archegonia have appeared. Examination of a 
number of prothallia at this date showed some with antheridia only, 
two with archegonia only, and some with both antheridia and arche- 
gonia. (All these prothallia were heart-shaped; crowded prothallia 
of irregular shape are not included.) Of the first, with antheridia 
only, there were two forms: (a) broadly heart-shaped, with antheridia 
in great numbers over much of the lower surface and crowded near 
the initials; and (0) younger prothallia, with fewer, more scattered 
antheridia, and none very near the notch. Of the second kind, I 
