Igr1] FERGUSON—IMBEDDED SEXUAL CELLS 447 
In this connection the condition represented in fig. 9b is very inter- 
esting. Here we have apparently the first three cells of an arche- 
gonium, in which the central cell has developed directly into what 
is to all appearances a sperm cell. This leads us to inquire at 
what point in the development of a prothallium the sexual nature 
of its cells is determined. Are we not too much accustomed 
in our thinking to combine the idea of sexuality with form and 
position and definite organs? It may be that maleness and 
femaleness have no necessary relation to form or position or 
sexual organs, but that sperms and eggs are developed in rela- 
tion to the sexual act or process, not as a necessary expression 
of sexuality. Should this be found to be true, then many cases of 
so-called vegetative fusion may come to be considered simply 
as instances of early or premature fertilization. To determine 
the point in the development of monoecious prothallia at which 
certain cells become endowed with sexuality, and the character- 
istic which makes them male or female, is one of the interesting 
but difficult problems which await solution. 
WELLESLEY COLLEGE 
WELLESLEY, MASSACHUSETTS 
EXPLANATION OF PLATES XXVI AND XXVII 
Unusual conditions in the development of the antheridia and the arche- 
gonia in Pteris. 
Fic. 1.—A young antheridium in which the first wall laid down is very 
slightly concave. 
Fic. 2.—A young, partially imbedded antheridium; the first wall laid 
down is parallel with the basal wall and not at all concave, while the second 
wall is very greatly arched. 
Fic. 3.—A similar stage to that shown in fig. 2, but the antheridium is 
more oo. imbedded and the outer cell arches but slightly 
Fic. 4.—The three-celled stage either of a normal Ce ations or of an 
imabedde, antheridium 
Fic. 5.—A later hae in the development of a partially imbedded anther- 
idium; the cover cell has been cut out in the usual manner. 
Fic. 6.—A slightly later stage in the development of a normal antheridium. 
Fics, 7 , 8.—Practically the same stage of partially or wholly imbedded 
thera as that shown in fig. 6; their position is entirely that of young 
ar egon 
