( 362 ) 
walls. These stain more readily by haematoxylon and other 
reagents to which ordinarily they do not respond. 
The endosperm becomes cellular at a very early stage, the 
formation of walls taking place first in its upper portion. 
Until an advanced stage is reached in the development of 
the embryo the lower end of the endosperm remains coeno- 
cytic, and is terminated by a long coecum which fits into a 
pocket of cells in the middie of the nucellus (fg. 726). The 
proportion of parts is shown better in an outline figure (r2¢). 
The cells which constitute this ‘‘ pocket” are much smaller 
than the others of the nucellus at this stage and by their 
protoplasmic contents (nucleus, cytoplasm, etc.) seems to be 
in about the same metabolic condition as those in other parts 
of the nucellus. These cells appear identical with those 
which surround the antipodal end of the embryo-sac at the 
time of fertilization. All the cells of the nucellus are then 
small and the subsequent enlargement of the others makes 
these appear smaller by contrast. Why these cells which 
surround the antipodals should not keep pace in growth with 
others is not quite clear, nor is it plain why they should not 
share the fate of others that are broken down by contact with 
the endosperm. They remain surrounding the extremity of 
the endosperm until long after the tissue of the nucellus has 
separated along the median line to the chalaza. The upper 
and the lower ends of the same mass of endosperm are shown 
in figures 725 and 726 respectively. The character of the 
cellular endosperm is entirely similar to that with which we 
have already become familiar in the preceding forms. The 
endosperm finally becomes entirely cellular, but while the 
outer layer consists always of a layer of small cells with 
dense cytoplasm, the cells of the central part expand to a 
size many times that indicated in figure 725, and show the 
merest trace of cytoplasmic contents. In this condition there 
is little evidence of its being at all active in the nutrition of 
the embryo. 
The development of the embryo proceeds apparently in 
about the same way which we have seen in the other forms. 
