539 
Erythronium americanum. 
sometimes the antipodal ones are the larger. The differences 
are specially noticeable in the quadrinucleate condition of the 
embryo-sac. The number of chromosomes could not be made 
out, as the nuclei were not seen in the process of division. 
The final condition of the embryo-sac is similar to that which 
has been shown to obtain generally. The embryo-sac, at the 
time of fertilization, is imbedded in a richly protoplasmic 
nucellus. There is a considerable amount of tissue in the 
chalazal region of the nucellus, but at the apex there is only 
a single layer of cells over the embryo-sac. The cells of the 
nucellus are strikingly marked off from those of the integument 
by their richness in protoplasm and by their avidity for 
stains. 
The pollen-tube penetrates the ovule in the usual manner 
and the egg becomes fertilized, the stages in the union of the 
male and female nuclei being made out with special facility 
on account of the large size of the elements. No attempt was 
made to demonstrate the existence of centrosomes and astro- 
spheres 1 . 
Fig. i shows the essential parts of a just fertilized ovule. 
Two nuclei are seen in process of fusion in the egg. The 
synergids have disappeared entirely, as is usually the case in 
Erythronium. The egg-cell subsequently divides into two 
generally, but not invariably, by a division at right angles to 
the axis of the embryo-sac. The first division is followed by 
others which have no fixed order or plane. 
In Fig. 2 a division is represented taking place in the upper 
cell of the two-celled embryogenic mass. The single layer of 
nucellar tissue over the apex of the embryo-sac is seen to 
be densely filled with protoplasm. Strasburger found the 
same peculiarity in Funkia , in which plant it is these ‘ inhalts- 
reiche Zellen ’ which give rise to the multiple embryos. In 
Erythronium , however, as before stated, all the tissue of the 
nucellus is rich in protoplasm. The same is true of Lilium 
canadense and species of Trillium , so the phenomenon is 
probably of general occurrence. 
1 Strasburger, Hist. Beitrage, IV. 
P p 2 
