1918] BUCHHOLZ—PINUS 195 
green the slides must be transferred rapidly through 95 per cent 
alcohol, absolute alcohol, alcohol-xylol, into xylol. The de-staining 
process is not checked until the sections have reached the pure 
xylol solution; thus only a short dip should be given into each 
solution. Although safranin with gentian violet, Delafield’s haema- 
toxylin, and iron alum haematoxylin with light green were all tested, 
they were found much less satisfactory than the iron-alum haema- 
toxylin with gold orange or the safranin with light green. 
FORMATION OF CORROSION CAVITY WITHIN GAMETOPHYTE 
The first change that is noticeable in the tissue below the arche- 
gonia is a starch deposit, which appears in the cells of this region 
about the time of fertilization, or a few days later. In the living 
gametophyte this deposit makes the tissue appear opaque, and it 
gradually spreads down into the central part of the gametophyte 
until this white opaque region comes to occupy a funnel-shaped 
region extending downward from the archegonia. About the time 
the embryos break through the bases of the archegonia the cells at 
the center of this opaque region break down, at first in the large part 
of the funnel nearest the archegonia. This forms the beginning 
of the corrosion cavity, an opening which, as it enlarges, assumes 
the shape of a slightly flattened trumpet. At the same time the 
starch-containing zone enlarges and becomes more conspicuous. 
Sections like that shown in fig. 1 indicate clearly that the diges- 
tive action of an enzyme on the endosperm doubtless precedes the 
elongation of the suspensor. The embryo is soon pushed so far into 
this cavity by the elongation of the latter that further elongation 
can only bring about its well known coiled and twisted condition. 
The importance of this mechanical action of the suspensor in keep- 
ing the embryo pressed into the bottom of the corrosion cavity is 
better realized when one tries to dislodge some of these embryos by 
dissection. 
Many ovules were examined in which the gametophytes had 
well developed corrosion cavities, yet no traces of embryos could 
be found in them, indicating that the archegonia may secrete the 
digestive enzymes to form the cavity even though the eggs have 
not been fertilized. Many sections of this kind may be found in 
