14 THE COMPARATIVE EMBRYOLOGY OF THE RUBIACEAE 
backwards towards the chalazal region. Its proper cytoplasm be- 
comes cut off by a transverse wall from the upper part of the em- 
bryo-sac (Pl. 2, Fig. 4). The other two antipodal cells surround 
themselves by walls, and take ultimately a lateral position. They 
are small and unequal in size and are usually more or less col- 
lapsed and apparently of little or no further value; and they over- 
stain in the manner of disintegrating cells. Not so, however, with 
the odd, basal antipodal, for in these forms (+. e., Vaillantia, Ga- 
lium, etc.), it appears to have a distinct and important physio- 
logical role. 
It has been supposed, since the publication of Hofmeister's 
classical researches on the embryology of the Phanerogams (/. ¢.), 
that antipodals were absent in those forms of the Rudiaceae studied 
by him, excepting Houstonia and Spermacoce. I have confirmed 
Hofmeister’s view as to Houstonia, but in addition I am prepared 
to show that antipodal cells are present in all Rudiaceae up to this 
time studied by me. The smallness of the structures in these 
plants, and especially the attenuated character of the basal anti- 
podal, together with the similarity of the other two to the adjoin- 
ing disintegrating integumental cells will readily account for the 
oversight. 
The basal antipodal cell is composed at first of cytoplasm which 
is tenuous, scanty and difficult to see. The nucleus comes to rest 
on one side of the cavity some distance removed from the trans- 
verse wall. 
Gradually the cytoplasm becomes more pronounced, stains more 
deeply and fills the elongating chalazal end. The apex becomes 
somewhat expanded into a knob which, as the cell lengthens, is 
plunged into the mass of megaspores. These are still evident, but 
are now on the way to disintegration as is attested by the fact that 
they lose all structure and become black and opaque with haema- 
toxylin, often making it very difficult to recognize the apical, 
knobbed part of the long antipodal. At the time when the basal 
antipodal is first cut off, there is a large mass of proteinaceous 
food in the place of the once archesporium, which as just stated, 
stains very deeply. As the embryo-sac as a whole reaches ma- 
turity, before the flower opens, the cytoplasm about the endosperm 
nucleus becomes abundant and dense, and the archesporial food- 
