98 BOTANICAL GAZETTE [AUGUST 
in the early development of the flower of Pyrus Malus. The 
lateral walls of the ovarian cavity are thus lined on the inside by 
carpellary tissue and the ovary is distinctly epigynous. Mean- 
while the moundlike apex of the floral axis has been slowly develop- 
ing and has come to occupy the entire ovarian cavity. It is in 
close contact with the walls of the cavity but never becomes united 
with them. In form, it is a compressed knob, flattened in the same 
plane with the spike. A transverse mid-section of the knob is oval 
in outline (fig. 14). A longitudinal section perpendicular to its 
broad surface is finger-shaped, while a longitudinal section in the 
plane of flattening shows the knob form (figs. 15, 17, 18). 
Hormetster in Loranthus europaeus and Trevs in L. sphaero- 
carpus found that the floral axis elongates between the carpels 
after they have appeared. According to BAILLON (1), the apical 
part of the floral axis is present throughout the development of 
the carpellate flower in Arceuthobium Oxycedri, just as we have 
seen it to be in Dendrophthora. ; 
The megasporangium (nucellus?) 
The floral apex is composed entirely of parenchymatous tissue 
and has a distinct epidermis. Parallel with the enlargement of 
the floral axis the cells subjacent to the sporogenous cells divide 
by periclinal and anticlinal walls (fig. 16). Later, when the 
uninucleate sac has been formed, it is partially surrounded by a 
tissue of a few cells in thickness, which has resulted from the 
divisions of these underlying cells. The contents of the cells of 
this tissue contain no starch, but have dense cytoplasm, their walls 
are thicker, and they stain more darkly than the cells of the other 
portions of the axis (fig. 17). The tissue thus formed about the 
young gametophyte is apparently nutritive in function, and may 
be regarded as the equivalent of a nucellus. TRreuB has shown 
that a similar tissue is formed about the archesporial cells in 
Loranthus Sphaerocarpus, but the cells are in this case filled with 
starch. In Arceuthobium Oxycedri there is apparently no nucellus 
formed as in the above mentioned cases. By the time the two- 
nucleate sacs are developed, the cells of the nucellus have become — 
much enlarged and the axis has become distinctly lobed (figs. 

