454 SUMMARY OF CURRENT RESEARCHES RELATING TO 
Karyokinetic Nuclear Division in Spirogyra.* * * § — Herr L. Mitzko- 
witsch gives the following account of the division of the nucleus in Spiro - 
gyra subsequa and jugalis. The large nucleus has a quadrangular form; 
within it is a dense nucleol e-like body which furnishes the material for 
the karyokinetic figures. While the nucleus becomes gradually round, 
this body forms filiform prolongations towards the periphery of the 
nucleus, where they combine with external achromatic filaments. At 
the same time chromatin bodies make their appearance in the previously 
homogeneous substance, surrounded by a light border. While the 
entire chromatin body becomes flattened into a disk which stands verti- 
cally to the filament, the sharp outline of the nucleus disappears, and 
it is no longer distinctly differentiated from the outer protoplasm. The 
chromatin bodies at the same time arrange themselves in a disk, from 
which proceed the achromatin-filaments. Each chromatin body now 
divides into two, and two parallel disks are formed, which gradually 
separate from one another. These daughter-plates acquire a more or 
less spherical form ; the coloured mass becomes again homogeneous ; 
and two daughter-nuclei resembling the parent nucleus take its place. 
Chemical Physiology of Spirogyra. j — A series of chemical analyses 
of the ash of Spirogyra nitida, grown under various conditions, have 
yielded to Dr. Mary E. Pennington the following results : — Chlorine 
and sodium are present in about the same proportion as in marine algae. 
Conjugating cells show a chemical composition which differs in almost 
every essential from that of the vegetative cell ; the behaviour of the 
tannin, and its marked increase in quantity, is striking. Under coloured 
screens the chemical composition of the algae differs according to the 
rays of light received ; starch was not formed under exclusive blue or 
yellow rays; under red rays the growth was even ’more rapid than in 
white light. 
Dissociation of the Cells of Spirogyra.j: — M. Devaux calls atten- 
tion to the fact that when the cells of a Spirogyra separate from one 
another, as they do with great ease, the ends remain rounded ; but that 
there is, in addition, a membrane in the form of a collar, forming a belt 
at the base of each terminal hemisphere. This shows that the cells are 
isolated by the gelification of the middle lamella, followed by a dissolu- 
tion and rounding off of each half-membrane, accompanied by a dis- 
integration of the outer lamella, which then forms the collar. The 
process of dissociation is due to a deficiency of oxygen in the water, 
and has nothing in common with the formation of thick-walled cysts. 
Arboreal Algae.§ — In addition to those already described, Herr 
W. Schmidle finds the following species of algae growing on trees in 
Ecuador: — Cephaleuros Lagerheimii sp. n., C. Karsteni , G. pulvinatus, 
and C. candelabrum, the last forming a connecting link between the 
genera Cephaleuros and Pliyeopeltis. 
* Warsaw, 1897 (1 pi.) (Russian). See Bot. Centralbl., 1S98, Beih., p. 401. 
t Contrib. Bot. Lab. Univ. Pennsylvania, i. (1897) pp. 203-59. 
+ P.V. Seances Soc. Sci. Phys. et Nat. Bordeaux, 1897, pp. 34-6. 
§ Hedwigia, xxxvii. (1898) pp. 61-75. Ber. Deutsch. Bot. Gesell., xv. (1897) 
pp. 456-9 (6 pis.). Cf. this Journal, 1897, p. 562. 
