428 
CECIL YAMPOLSKY 
In the heterosporous ferns, as in the seed plants, the sex of the gameto- 
phyte is determined before the reduction division. Thus in Salvinia the 
sori are differentiated as to sex in the sporophytic generation. In the 
Marsileaceae the differentiation is not one of sori but of sporangia. This 
is not absolute, because microsporangia have been induced experimentally 
to produce macrospores and macrosporangia, microspores. Shattuck (1910) 
has been able experimentally to arrest the formation of the macrospores 
and microspores in Marsilea quadrifolia. He did this by subjecting young 
sporangia to unf^avorable conditions for growth, such as reduction in light, 
and by means of cold water spray. Occasionally he found that when 
microspores were thus retarded, macrospore-like cells were produced. He 
also found microspores in macrosporangia. 
In both dioecious and monoecious seed plants the sex of the gameto- 
phyte is fixed. However, in so-called perfect flowers the sex organs as 
they develop are transmu table. The sex of the gametophyte generation 
is prevailingly determined before the reduction division; thus as a rule the 
macrosporophyll will bear the macrospore, the microsporophyll the micro- 
spore ; but pistillody of the stamens and staminody of the pistils have been 
repeatedly observed, that is, a macrosporophyll may be transmuted into 
a microsporophyll or vice versa. When reduction occurs the sex of the 
gametophyte has already been fixed. 
While morphologically the gametophyte generations in the flowering 
plants appear to be unalterable, so that a macrogametophyte produces 
only eggs and a microgametophyte only male gametes, it has been urged 
that in dioecious phanerogamic plants none the less the gametes of either 
one of the gametophytes may be of two kinds, male-determining and fe- 
male-determining. The cytological investigations in animals in which 
either the male or the female may produce two kinds of gametes, as evi- 
denced by their nuclear constitution, have been made the basis of views 
favoring the existence of a similar condition in plants. If we briefly ex- 
amine the process whereby a female gametophyte is produced, we shall 
find it difficult to reconcile the assumption that there are two kinds of 
eggs, male and female, without bringing in accessory hypotheses. If we 
assume that the homosporous ferns are the ancestors of the seed plants, 
we note a distinct specialization in the gametophytes of the seed plants 
as contrasted with the ferns. The gametophyte of the homosporous fern 
bears both sperms and eggs. The gametophyte is capable of producing 
both gametes but both are distinct, the sperm a motile gamete,. the egg a 
stationary gamete. In the seed plants the gametophytes may be conceived 
as having developed from a monoecious gametophyte of the fern through 
the suppression of one or the other of the gametophytes, thus a macro- 
gametophyte through the suppression of the microgametes of a gameto- 
phyte and a microgametophyte through the suppression of the macro- 
gametes of a gametophyte. Such a development leaves no room for the 
