220 BOTANICAL GAZETTE [SEPTEMBER 
The great variety in form and behavior exhibited by antipodal 
cells, together with haustorial structures of many types, has been 
so well summarized (COULTER and CHAMBERLAIN 3) that further 
comment here is unnecessary, since Physostegia offers nothing 
essentially new. 
At the time of fertilization the general aspect of the embryo 
sac, together with its position in the ovule and its relation to the 
vascular supply, are as shown in fig. 8. The usual configuration 
of the egg apparatus is that figured here, but in other cases it 
exhibits considerable variation from this. In regard to the posi- 
tions of the nuclei and vacuoles, the synergids represented in fig. 
7 show striking similarity to the egg, and it is conceivable that at 
least the larger one might function as such. 
The pollen tube, which has grown down the style into the 
_ sporangial chamber, makes its way around the stalk of the ovule, 
or at times directly over its summit, to the micropyle, through 
which it enters the embryo sac. Clear cases of fusion of the male 
nucleus with that of the egg were not observed, but the presence 
of the pollen tube within the sac, the disorganization of the syner- 
gids, the immediate elongation of the egg with divisions to form an 
embryo, and a triple fusion in the central region of the sac (fig. 9) 
make it reasonably safe to conclude that fertilization of the usual 
type occurs. 
The formation of the endosperm is of considerable interest. 
It is initiated by the division of the endosperm nucleus, which 
occurs in the narrow region of the sac near the haustorial antip- 
odal, as shown in fig. 10. The spindle has a transverse orienta- 
tion and is very broad, owing to the large number of chromosomes 
present. The division is accompanied by a longitudinal wall 
running through the middle of the sac, as shown in fig. 11, which 
represents a sac cut in a plane at right angles to that of fig. ro. 
Here the wall is still in process of formation, spindle fibers being 
evident at its extremities. Extension continues until it comes 
into contact with the sac wall at or near the end of the endosperm 
lobe (fig. 12), while in the micropylar lobe it was not observed 
to do so, and probably ends freely. The nuclei now lying in the 
two resulting parts of the embryo sac divide, forming transverse 
