70S 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
by Treub in the Casuarinese. It descends from tlie tissue at the base of 
the st.ylar rudiments, and, running parallel with the vascular bundle of 
the rapha, turns abruptly up into the nucellus on reaching its chalazal 
region. Various adaptations to chalazogamy also occur in the struc- 
ture of the embryo-sac. 
Herr S. Nawascliin’s * observations agree to a large extent with 
those of Miss Benson, and confirm his previous statement as to the 
chalazogamic character of the Betulaceae. He further adds Ulmus to 
the list of chalazogamic plants, this genus presenting an intermediate 
condition between the Casuarineae and the Amentiferce. The pollen- 
tube does not here reach the nucellus through the micropyle, but forces 
itself through the tissue of the short style, then passes through the 
funicle to the ovule, reaching the apex of the nucellus by piercing both 
integuments. 
Embryology of Ephedra.j — M. P. Jaccard has carefully studied the 
development of the embryo of Ephedra helvetica (Gnetacese). The fol- 
lowing are the most important results : — 
The female flower is composed of a sessile ovule at the apex of a 
secondary branch. It has a single integument, and is surrounded by 
a shell ( coque ), which is composed of bracts, and is not, therefore, mor- 
phologically an ovary. The embryo-sac results from the enlargement 
of the lowest of the 3-1 cells due to the division of a primordial 
mother-cell. Its development comprises four periods, — the nuclear 
period, that of the formation of the primary endosperm, of the corpuscles, 
and of the secondary endosperm. The free nuclei of the embryo-sac all 
divide simultaneously, and present the] same karyokinetic figure. The 
number of chromatic segments of the nucleus is less in the endosperm 
than in the other tissues. The archegones are developed from primary 
endosperm-cells similar to the rest. Before impregnation the epiderm 
of the nucellus is transformed, in its free portion, into a layer of tran- 
sitory reserve-substances, but its large cells persist until the formation 
of the integument of the seed. 
The pollen-grain contains, when mature, three nuclei, a large central 
nucleus surrounded by protoplasm (Belajeff and Strasburger’s antheridial 
cell), and two vegetative polar nuclei, one of which is the nucleus of the 
pollen-tube, while the other may be regarded as the homologue of the 
prothallium-cells of Conifers, or as a detached nucleus of the antheridial 
cell. The nucleus of the antheridial cell divides into two generative 
nuclei, one only of which takes an active part in impregnation. 
After impregnation the archegone is filled with a mass of condensed 
protoplasm and of nuclei resulting from the disorganization of the cor- 
puscular envelope. The archegone then becomes disorganized ; and in 
its place is formed a lignified tissue to which the author applies the 
term columel. The columel retreats towards the middle of the endo- 
sperm, and bears at its apex the privileged embryo, the only one which 
developes. It plays, therefore, the part of a primary suspensor; the 
remaining abortive embryos have no pro-suspensor. The secondary 
suspensor is well developed, and is the result of transformation of the 
* Eer. Deutsch. Bot. Gesell., xii. (1894) pp. 163-9 (6 figs.). Of. this Journal, 
1893, p. 656. f Bull. Soc. Vaud., xxx. (1894) pp. 46-84 (8 pis.). 
