108 
ON THE BLOOD-LIKE PHENOMENA. 
many days, and with perfect leisure, accurately examined the appear¬ 
ance, and made microscopical observations on the colouring mass. 
The flakes consisted of small spiral, or longish irregular hunches of 
oscillatorise threads, which were enclosed in a gelatinous sheath, and 
the flakes neither resembled one another nor the threads in each flake. 
In the glasses placed besides me, I observed that the flakes, during 
the heat of the day and in sunshine, floated together on the surface 
of the water. During the night, and when the glasses were shaken, 
they descended to the bottom. After some time they returned to the 
surface. The observation made by Dr. Engelhardth on Lake Mur- 
ten, was very similar to this appearance, and the delineation of the 
single threads by De. Candolle, informs me he has preserved no dried 
specimen of that substance, for which reason no comparison can be 
made. The gelatinous covering, and the union of many threads into 
very small spiral groups, give to the substance of the red sea a peculiar 
character, which entitles it to form a particular genus of alga. 
Trichodesmium erythreum. Char. gen. Fila septata fasciculata 
nec oscillantia, fasciculi discreti niuco involuti sociales libere natantes. 
I know a very similar green body, which I have often observed at Leip- 
sic and Berlin, and which entirely fills the water, giving it a greenish 
hue. I call it Trichodesmium flos aqua, because I do not find it 
enumerated among the commonly mentioned forms of this kind. 
The appearance of the Red Sea was not permanent but periodical. 
I observed it four times, viz. -on the 25th and 30th of December 
1823, and on the 5tli January 1824. We brought along with us for 
the Royal Collection specimens taken from the sea shore, and dried 
on paper and sand. More particular details in regard to it will be 
found in the Symboli Physici of Dr. Hemprick’s journey and my 
own. 
In 1829, 1 had an opportunity in Siberia of making my most .re¬ 
cent observations on blood-red water. In the steppe of Platow, be¬ 
tween Barnaul and the lake of Koliwan, on the 24th July (5th Au¬ 
gust, O. S.,) while intending to take a survey of the vegetation of the 
steppe, I found a fen with a pool of water, in a low land in the im- 
diate vicinity of the postotation. The dark blood-red colour of the 
water was very striking, even at a distance. I therefore during 
breakfast made an excursion to the place of the phenomenon. I found 
that the colour was confined to a slimy surface, which in different places 
formed a shining skin. In some places the water was troubled with 
red colouring matter, which in many places passed into a greenish hue. 
The red colour was darkest on the edge of the marsh. In some 
spots, indeed, it formed a red jelly, because the water began entirely 
