ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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Las these sexual cells inclosed in cell-walls of cellulose. This is the 
future embryo-sac. There are no antipodals. 
Only a single ovule in each ovary is fertilized. The pollen-tube 
which impregnates it descends the axial stylar cylinder, crosses the 
bridge and the tissue which unites the ovule with the wall of the ovary, 
traverses the chalaza, and becomes ruptured about the middle of the 
nucellus, the apical portion being the only one which takes part in 
fecundation. This portion never enters the micropyle nor the embryo- 
sac, but becomes firmly attached to the wall of the latter at a point at 
some distance from the sexual apparatus ; but the actual process of im- 
pregnation has not as yet been observed. During the development of 
the embryo-sac numerous endosperm-nuclei arc formed, and subsequently 
the embryo makes its appearance. Its development resembles that in 
normal Dicotyledons. 
M. Treub regards these facts as sufficient to warrant the separation 
of the Casuarinem as a distinct primary section of Angiosperms, to 
which he gives the name Chalazogams, classing the Monocotyledons 
and Dicotyledons together under the term Poiiogams. The Chalazogams 
are not intermediate between Gymnospcrms and Angiosperms, but con- 
stitute the lowest division of the latter. 
The preparations were treated with eau-de-Javelle, and stained by 
Bismarck-brown. 
Pollen-tube of Gymnosperms.*— Herr W. C. Belajeff contests the 
ordinary view that it is the larger cell alone in the pollen-grain of 
Gymnosperms that takes part in the process of impregnation, or, indeed, 
that it is the true generative cell. The observations were made chiefly 
on Taxus baccata. 
The ripe pollen-grain of Gymnosperms consists of one large and 
several small cells ; the latter are cut off in succession from the large 
cell, which is an argument against the theory that they are the survival 
of a male prothallium. At the time of fertilization there are found — 
surrounding the two nuclei resulting from the bipartition of the nucleus 
of the larger cell, which has wandered to the extremity of the tube — a 
number of small cells, which are generally stated to have been formed 
at the spot where they are found. This view the author believes to be 
incorrect. 
One of the small cells resulting from the division of the large cell, 
the anterior one, does not become resorbed, as is generally stated ; but, 
in the course of development of the pollen-tube, wanders to its extremity, 
in company with the nucleus of the large cell ; the other posterior small 
cell breaks up, but its nucleus becomes detached, and also takes the 
same course. The end of the pollen-tube swells up, and often puts out 
outgrowths in various directions. The nucleus of the small cell over- 
takes the wandering cell ; the latter rounds itself off, increases in size, 
and its nucleus divides into two. In the process of fertilization it 
appears to be one of the daughter-nuclei of this wandering cell, together 
with the protoplasm that surrounds it, that pass into the oosphere ; the 
other daughter-nucleus, with the membrane, remains in the pollen-tube. 
The fate of the nucleus of the large cell could not be determined. 
* Ber. Deutsch. Bot. Gcscll., ix. (1S91) pp. 280 6 (1 pi.). 
