( 390 ) 
by the endosperm and that the embryo in its early stages is 
nourished by the products of this digestion, though not di- 
rectly. Although anatomical evidence only is at hand on 
this question, the facts observed were all in harmony with the 
above conclusion. The endosperm grows at first at the ex- 
pense of the embryo by utilizing the materials which it ob- 
tains for its own development, but when the embryo at a later 
time begins its growth it does not digest the endosperm, but 
apparently absorbs the material supplied by it. That the 
endosperm is only temporarily functional in this way is indi- 
cated by its appearance in those stages of embryonic develop- 
ment which follow the differentiation of cotyledons. At 
about this time the ovule has almost assumed the proportions 
of a ripe seed and the nucellus is able to offer no resistance 
to the growth of the embryo or to the flow of those nutritive 
substances which enter through the chalaza. The endosperm 
very early replaces most of the nucellar tissue and before the 
embryo is far along inits growth there is little of it left. The 
endosperm loses most of those plasmatic characters which 
indicate an active metabolism, and becomes of very thin and 
watery consistency. 
That endosperm sometimes acts as a digestive medium in 
absorbing the tissue of the nucellus has been shown by John- 
son,” in the case of certain species of the Piperaceae. 
Haustorial extensions of the endosperm are more or less 
common in many families among the Sympetalae. Balicka- 
Iwanowska‘ found in the Campanulaceae haustoria devel- 
oped from the endosperm which penetrated the integuments 
of the ovule. From these and other observations the gener- 
alization was made that such haustoria were formed only in 
ovules with thick integuments. Other investigations in the 
Campanulaceae have been conducted by Hegelmaier.* He 
found that the endosperm of Specular¢a extends toward the 
chalaza in a string-like mass which may sometimes become 
divided by walls transversely and sometimes longitudinally. 
Other investigations on the Lobeliaceae and the Stylidiaceae 
reveal haustorial appendages of the embryo-sac which serve 
