532 
basis, not as something which we are striv- 
ing to prove at all hazards, progress in in- 
vestigation is impossible. 
1. The first theory as we have seen was 
that proposed by Hofmeister who regarded 
the synergids and eggs as ‘ embryonal vesi- 
cles’ or ‘germinal vesicles,’ and _ there- 
fore the equivalent of eggs. The supposed 
variable number of antipodals when they 
were present represented the prothallium. 
It is interesting to note that at the present 
time a number of botanists are coming to 
recognize the synergids as potential eggs, 
thus confirming Hofmeister’s interpretation 
of the egg apparatus. 
2. The proposal by Schacht (1857-8) of a 
‘filiform apparatus’ suggested by certain 
folds or strize on the synergids, which were 
supposed to act as a conductor of the pollen 
tube to the egg, led Strasburger (Bef., p. 73, 
1877), Pringsheim and others to recognize 
in this the ventral canal cell. The egg ap- 
paratus thus came to be recognized as the 
archegonium, with the synergids as neck 
cells, while the antipodals represented the 
prothallium. This was the prevailing view 
at that time, and was adopted by Sachs in 
the earlier editions of his text-book. A 
very similar view of the embryo-sac has 
recently been stated by Tretjakow. 
3. The third view of the homology of the 
embryo-sac was the outgrowth of the studies 
of Warming and Vesque, in which the eight 
nuclei of the embryo-sac were interpreted 
as spores, the egg apparatus representing 
one tetrad, and the antipodals a second 
tetrad of spores, each spore homologous 
with the pollen grain. This had its origin 
in the endeavor of Warming to homologize 
the processes of cell division in the ovule 
with those in the anther, both of which 
were looked upon as sporangia. The larger 
cell which gives rise to the so-called axile 
row in the nucellus, and which is either the 
subepidermal cell, or a derivative of it 
when a ‘tapetum’ is present, he called the 
SCIENCE. 
[N.S. Vou. XIII. No. 327. 
primordial mother cell of the embryo-sac, 
and it is so termed by some at the present 
day. This cell Warming recognized as the 
young archesporium, comparable with the 
tetrahedral cell in the young fern sporan- 
gium. This primordial mother cell, as is 
well known, divides into an axile row of 
several cells, 2, 3, 4, etc. This axile row 
Warming considered the mature arche- 
sporium, each cell being homologous witha 
pollen mother cell, and he termed them 
special mother cells. The lower one only 
developed into the embryo-sac, forming two 
tetrads, one at either pole, while the other 
special mother cells disappeared. The egg 
nucleus is then called the privileged spore. 
His conclusions here do not appear quite 
consistent with his hypothesis, since he de- 
rives two tetrads (8 spores) from a single 
special mother cell. ; 
4. Vesque (1879), however, accepting in 
the main Warming’s views, attempts to 
show that the two tetrads are derived from 
two special mother cells. The cells of the 
axile row he regards as the mature cells of 
the archesporium, that is, special mother 
cells, and numbers them 1, 2, 8, 4, 5, etc., 
according to the number present in different 
species, beginning with the uppermost cell 
(the one at the micropylar end). No. 1, 
then, the uppermost cell, divides to form 
a tetrad, the egg apparatus; while No. 2 
forms one or several antipodals, and makes 
up the larger portion of the embryo-sac. 
The wall between 1 and 2 dissolves and dis- 
appears, so that the embryo-sac is supposed 
to form by the fusion of these two cells. 
It is not necessary to dwell further upon 
Vesque’s view, since he gives such an im- 
perfect account of the processes of develop- 
ment which take place here, and since 
subsequent studies show that in a very 
large majority of cases it is the lower cell 
of the axile row which gives rise to the 
embryo-sac. But it is of interest to note 
his attempt to harmonize Warming’s view 
