No. 457.] EMBRYO OF THE ANGIOSPERMS. 29 
ation of the haustrum is always apparent so that their protocorms 
are essentially haustral structures from which the sporophore 
sooner or later develops as an outgrowth. In Phylloglossum the 
ontogenetic acceleration of the haustrum is most pronounced, a 
large bulbous protocorm resulting, from which the sporophore is 
differentiated at a quite late period (Fig. 2). As the protocorm 
of this plant becomes geophilous, it develops leaf-like lobes of 
tissue which carry on photosynthetic work. Bower ('94) terms 
these protocormal leaves, protophylis, to distinguish them from 
the leaves of the metacorm, the euphylls. With the specializa- 
tion of the root as the earth-boring haustrum and the euphylls as 
the photosynthetic areas, the geophilous protocorm with its pro- 
tophylls disappears from the ontogeny of the higher pteri- 
dophytes as we have already found. Perhaps, however, the first 
leaf of some of these should be interpreted as a protophyll rather 
than a euphyll. 
In the embryogeny of Lycopodium and Selaginella an out- 
growth from the protocorm serves to carry the embryo down 
into the tissue of the gametophyte. This protocormal organ, 
the suspensor, is limited to the lycopods among the pteri- 
dophytes but is of general occurrence in the embryogeny of the 
angiosperms. 
The positional relation which the metacorm bears to the proto- 
corm is remarkably different in different cryptogamic embryos. 
In the Bryophyta the axis of the metacorm is coincident with the 
axis of the protocorm, the haustrum of the latter developing into 
the haustrum of the mature plant. With the advent of the 
root as the haustral organ of the metacorm, the position in which 
it is differentiated in relation to the sporophore determines the 
primary axis of the metacorm. In some embryos the root is dif- 
ferentiated out of the body of the protocormal haustrum, while 
in others it appears as an outgrowth from this structure. In 
Botrychium obliquum and Equisetum, the root appears diamet- 
rically opposite the sporophore and hence the metacormal axis 
transfixes the protocorm, the tissue of the latter becoming a per- 
manent' part of the metacorm. In Selaginella, the metacormal 
axis is differentiated through the tissue of the protocorm, the 
suspensor being on one side of the axis, and the cotyledon on the 
