STRUCTURE AND HISTORY OF PLAV. 245 
in the delta, since floods are so frequent ; whereas, in point of fact, attached 
reed (reed-swamp) is far more abundant than Plav. 
(11) “In weniger tiefen Seen wie z. B. in den Seen von Bräila, bildet 
sich der Deltaplaur nicht. Aber auch in diesen Seen gibt es eine Art 
schwimmenden Schilfs. Dort werden dureh den Tritt des Viehs, durch 
Eisstoss, Gefrieren, etc., grosse Stücke alten Schilfs losgetrennt, die mit 
einander durch ihre Wurzeln verbunden sind. Diese Stücke schwimmen 
auf dem Wasser, werden vom Winde fortbewegt, und die Fischer nennen sie 
€ Plavie” oder * Plaghie? an andern Orten wiederum ‘ Coscove ? [Cosheove], 
‹ Cocioace’ oder * Culare”.... Solche kleine Inseln gibt ез: bei Somova, 
am nordlichen Teil des Brates (Bratish), selbst im Siutghiol bei Constantza 
u.s. w., die durchwegs tiefe Seen sind. Diese schwimmenden Inseln haben 
jedoch nichts mit dem Plaur des Deltas zu tun, der eine ganz andere Bildung 
ist, Es kommt allerdings vor in manchen Seen wo ähnliche natürliche 
Bedingungen wie im Delta sind—d. В. wo man ein ruhiges, klaares sauer- 
stoffarmes, tiefes Wasser hat, mit einem weichschlammigen Boden, mit 
regelmüssigen periodischen Schwankungen des Wasserspiegels etc.— dass 
dort das Rohr Plaurühnliche Formationen bildet. So ist es z. В. in den Seen 
Vederoasa, Somova etc. doch sind das nur [Formationen von] ganz kleinem 
Umfang aber dafür sehr interessant, denn sie zeigen urs im kleinen die Art 
wie die grossen Plaurbestünde des Delta sich gebildet haben." 
Т examined some of the floating-reed of the Somova chain of lakes (near 
Tulcea), the “ Prundoae” of the local fishermen. I detected no differences 
from Plav in essentials, that is to say, in structure and origin : Prundoae is 
merely Plav of small extent, but its soil is grey, that is to say, almost entirely 
inorganic *, except for the few centimetres of organic soil which are aggregated 
at the top of the Prundoae—the contribution of the land-plants rooted in it. 
The grey soil of Prundoae is readily accounted for by the fact that the Somova 
lakes are not in the delta and the floods are therefore much greater (see 
рр. 237 & 238). The waters of the Somova lakes were, at the time that 
I visited them (about October 18th, 1913), still grey with the fine river-borne 
silt which they held in suspension. To sum up, the environment in some 
spots outside the delta, although somewhat similar to that of the delta, 
differs sufficiently to prevent the frequent formation of Plav. 
(12) “Im Prozesse der ständigen Umwandlung der Seen spielt der Plaur 
* In the Museum of the Geological Institute of Bucharest there is a specimen of “ Plav " 
which as regards structure and soil, though not as regards thickness—it measures only 0:5 
to 0'6 m. (about 2 feet)—is an average sample of the delta Plav. The low organic contents 
iust be connected with its place of origin—near the Dunavatul | Dunavatsul J, 
of its soil п 
aterways of the southern portion of the delta, and as such having a 
one of the largest w 
fairly rapid current and therefore able to carry a considerable quantity of inorganic silt. 
I do not regard this specimen, which is labelled Plav, as typical delta-Plav but as Prundoae, 
which, as I remarked above, does not differ from Plav structurally but only in its size and 
in the kind of soil it holds. 
