1868. | Botany and Vegetable Physiology. 383 
though these animals often sunk, the water still in their absence 
retained its peculiar colour. On further examination he found the 
cause of this to be a vast abundance of Diatoms, chiefly of one 
moniliform species, the name of which does not appear to have been 
determined. The Medusx and other animals were found to feed on 
these plants, and, as is well known, are themselves the food of the 
whale, hence the presence of those vast cetaceans in the “black 
water.” The same Diatom (with others) is the cause of the brown 
“yotten ice” of explorers ; but this fact has been previously noticed 
by Dr. Sutherland. 
A paper by Dr. C. Collingwood on the same subject, read at the 
Microscopical Society in March, appears in the ‘ Microscopical Jour- 
nal.’ In this the cause of the coloured water in the Indian ocean 
and China sea is investigated ; as in the former case, it is due toa 
minute Alga, not a Diatom, but referable to Trichodesmium, a genus 
of Oscillatori#. The appearance produced on the water is that of a 
yellowish-brown scum, the sailors call it “sea-dust.” The plant 
consists of short filaments, composed of a single line of cells, com- 
bined into a cylindrical unbranched fibre. A good many of these 
are aggregated into little bundles, having the appearance either of a 
“sheaf” or a “wedge,” according as they are in close contact either 
at the middle or at one end. A species of Oscillatoria (?) occurs 
with it. Dr. Collingwood has never seen any red discoloration of 
the sea, such as is said to have been observed by many persons in 
the Red Sea and Persian Gulf, and also in the North Pacific, and 
which is caused by one or more closely allied species of Tricho- 
desmium. 
Hederaceex.—Dr. Seemann gives another instalment of his revi- 
sion of this order in the May number of the ‘Journal of Botany.’ 
Kissodendron, Didymopanax, Aralia, and other genera are passed 
in review; and the characters of two new genera Dipanax and 
Triplasandra are defined. The author however appears to have 
a tendency to create genera in this order on somewhat slender 
grounds. 
British Botany.—The curators (Mr. Baker and Dr. Trimen) of 
the London Botanical Exchange Club have published their annual 
Report for 1867. Three new plants are described: Rosa Hailstond, 
Baker (a variety of R. canina), from Yorkshire; the true Allium 
carinatum, Linn., from Nottinghamshire; and Salix Graham, 
Borrer, from Sutherland. The Report includes notes on the nume- 
rous interesting or rare species, native and introduced, which have 
been communicated to the Club during the year. 
The recently discovered Viola Arenaria, D.C., is recorded by 
Mr. James Backhouse from a new locality “several miles distant ” 
from the only previously known one in Teesdale, Durham. 
A Carduus, said to be new to Britain, has been gathered in Ross- 
