614 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
BOTANY. 
A. GENERAL, including the Anatomy and Physiology 
of the Phanerogamia. 
a. Anatomy. 
(1) Cell-structure and Protoplasm. 
Function of the Nucleus.* — Herr J. Gerassimoff has found that cells 
without nuclei occur in Sirogonium and in various species of Spirogyra. 
As the neighbours of the non-nucleated cells have two nuclei, the 
absence of the nucleus is explained by supposing that in cell-division 
one of the daughter-cells retains both of the daughter-nuclei. Herr 
Gerassimoff was able to study these non-nucleated cells in their natural 
conditions, and found that they were short-lived. In the binucleated 
cells the nuclei lay opposite one another in the peripheral protoplasm 
and on a line bisecting the cell transversely. The author’s theory is 
that the nucleus is the seat of a specific energy, such that two nuclei 
repel one another. 
“Attractive Spheres” in Vegetable Cells (Tinoleucites).f — M. L. 
Guignard calls attention to the fact that, in studying the phenomena 
accompanying nuclear division in animals, especially at the moment of 
fecundation, and later in the embryonic tissues, a special element known 
as an “ attractive sphere ” has been observed. Hitherto the presence of 
these bodies has not been noticed in plants, but the author states that 
they exist in the primordial mother-cells of the pollen of certain plants 
( Lilium , Listera , Naias ), in the mother-cell of the embryo-sac, &c. 
These bodies rather merit the name of “ directing spheres,” since they 
govern the division of the nucleus, and are transmitted from cell to cell 
without discontinuity during the whole life of the plant. 
M. E. De Wildeman J confirms M. Guignard’s observations on all 
important points, and finds the phenomena to agree closely with those 
observed by Van Beneden in the ovum of Ascaris megalocephala. In its 
typical condition the attractive sphere consists of a small central mass 
or centrosome, which is coloured somewhat more strongly than the 
surrounding protoplasm by staining reagents. This mass is surrounded 
by a delicate hyaline zone, and this again by a thicker granular zone; 
in certain cases the granulations of the latter have a radial arrangement, 
especially during the phases of division. When the cell is at rest, 
the attractive sphere is situated near the nucleus ; when the cell is 
dividing, the sphere divides into two, one of the new spheres being 
placed at each pole of the spindle. Very typical examples of these 
attractive spheres occur in Spirogyra , especially S. nitida ; they have 
also been observed in the mother-cells of the spores of Anlhoceros Isevis 
and Isoetrs Durieui , and in those of several mosses, Funaria hygro- 
metrica , Ceratodon purpureus, and Bryum csespitosum. For the observa- 
tion of these structures the fixing material used should not be alcohol, 
* Bull Soc. Imp. Nat. Moscou, 1890 (1891) pp. 548-54 (3 figs.), 
t Comptes Rendus, cxii. (1891) pp. 539-42. 
t Bull. Acad. Roy. Sci. Belgique, lxi. (1891) pp. 594-602 (1 pi.). 
