SCIENTIFIC SUMMAKY. 
509 
capsules respectively divide in their equatorial lines, and expose the sheaths of 
the sporangial frustules. (6.) The sheaths become elongated, and at the same 
time present thread-like rings on their surface, dimmishing gradually in 
thickness toward each extremity, but in close approximation throughout, 
except at the middle, where there is an interval of about -b-oVit of inch 
between them, or three times the breadth of the neighbouring rings. (7.) The 
sheaths, elongating, carry out the ends of the capsules upon their extremities. 
(8.) The hemispheres of the capsules disintegrate into short fusiform, curved, 
thread-like filaments. (9.) The sheath is fully formed, and the sporangial 
frnstule appears within it. (10.) The empty sheath presents a longitudinal 
dehiscent fissure, through which the sporangial frnstule obtains its exit. 
Baccillaria Paracloxa in Fresh Water. — The Kev. Kobert C. Douglass 
writes to the Editor of the Microscopical Journal (April) to deny that the 
discovery of B. paradoxa in fresh water is a new fact, as announced in the 
jirevious number of that periodical. It appears that he recorded in 1851 
{Botanical Gazette) the detection of this species in a gathering from ditches 
near the river, a short distance above the town of Stafford. He adds, too, 
that on more than one occasion, after the publication of that notice, he found 
bacciUaria in gatherings from the same system of ditches and on both sides 
of the river. It is remarkable that, though Stafford is far from the sea, 
.salt-loving phanerogams have been found in its neighbourhood — e.g., Glaux 
Maritima and Bumex Maritimus. There are salt-works about five miles 
from the town, in the direction of the localities of these plants, but the 
district where Mr. Douglas found baccillaria is in the opposite direction and 
far removed from their influence. 
Candidates for the Correspondent Membership of Botanical Section of 
Academy. — In the first rank was placed Hofmeister, of Heidelberg ; in the 
second, De Bary, Asa Gray, Dr. Hooker, M. Parlatore, and M. Pringsheim. 
Hofmeister was elected by thirty-two out of forty-four votes. Dr. Hooker 
obtained nine, and Parlatore three. 
CHEMISTPY. 
An Easy Method of Preparing Oxygen. — A convenient method of pre- 
paring oxygen in large quantities being a desideratum, Herr Eleitmann 
describes a mode which he adopts, and which possesses much scientific 
interest. He was led to the process by observing that on heating a concen- 
trated solution of chloride of lime with only a trace of freshly prepared 
moist peroxide of cobalt, the hyperchlorite of lime was completely decom- 
posed into chloride of calcium and oxygen. Kepeated quantitative experi- 
ments, the results of which he has lost, convinced him that the whole of the 
oxygen was evolved, and that only chloride of calcium and no chloric acid 
was formed. The evolution of oxygen commences at about 70° or 80°, and 
continues in a regular stream, with a slight frothing of the liquid. The 
action of the peroxide of cobalt in this case, it is clear, is exactly like that of 
