BLODGETT—BULBS OF ERYTHRONIUM 365 
to be that of transfer agents for substances from the chalaza 
to the embryo sac, and thence to the forming embryo and 
dosperm. 
When the seed reaches its full development the embryo sac 
is filled with hard endosperm of reserve cellulose. The cells in 
the endosperm have their longer axes directed inward from the 
periphery, curving somewhat toward the micropylar end of the seed. 
Through the center of the endosperm there is sometimes the same 
cellular endosperm as elsewhere, more frequently this is nearly solid _ 
_ Inoisture can more promptly reach the embryo by this path than 
Would be the case if only thick-walled endosperm were present. 
_ At the base of the seed the endosperm shows considerable shrinking, 
_With the remnant of the nucellus remaining in contact with the 
endosperm for a small area near the center. This secures contact ° 
_ between the hard endosperm and the spongy spur, and even when 
_the spur has disappeared the inner layers of the tissue at the chalaza 
temain in intimate contact with the base of the endosperm. As 
_ the endosperm along the axis of the embryo sac is the last to be 
- deposited, it is probable that the mass of spongy cells in contact 
With the base is of advantage in the imbibition of water preliminary 
to germination. In different seeds the exact appearance of the 
Central portion of the endosperm varies from nearly solid, with 
Infrequent cell cavities, to a condition similar to that of the pe- 
: ripheral endosperm; the latter is less common than is the solid 
Core mass. The exact distribution of the cell cavities in the endo- 
‘Sperm is probably in close relation to the moisture conditions 
during the late stages of ripening of the seed. In germination the 
embryo first enlarges to occupy the space filled by the spongy 
‘avities toward the periphery, and the endosperm is absorbed almost 
completely. 
