STRUCTURE AND HISTORY OF РГАУ, 241 
tall reed, through which, during times of flood, the waters often escape, 
converting sea and Balta into an almost continuous whole. The beach, 
which is one of the few cart-roads of the delta, is then disturbed by numerous 
runnels issuing from the Balta, and travellers are on these occasions com- 
pelled, in some places, to drive in the sea itself along a sand-bank under 
water. 
Introduction to Plav. 
Before proceeding with the detailed account of my work on Flav, I will 
quote Dr. Antipa's more important observations and conclusions concerning 
its structure and origin, and, since we are in some cases at variance, 
I will indieate briefly after each where we differ. I should like to point out 
that Dr. Antipa does not profess to have treated Plav exhaustively ; he has, 
in fact, expressed the hope that some botanist or agricultural geolopist will 
take up its study more fully than he was able to do. In his book only 
nine pages * are devoted to Plav, and they include figures in the text. 
(1) * Die Plaur t-Decke hat eine mittlere Dicke von 0:90 m.-1 m. [2 feet 
11:5 inches-3 feet 3 inches] und wird aus dicken, in einander verflochtenen 
und durch ihre wie Barthaare feinen Wurzeln zusammengebundenen Schilf- 
rhizomen gebildet welche sich untereinander verfilzen und zusammen eine 
schwimmende $, mehr oder wenige kompackte Masse darstellen.” 
I took some forty sections through Plav and found its thickness to 
be between ("8 m. and 2 m. (about 2 ft. 6 in. to 6 ft. 63 in.). These 
measurements refer only to the compact portion of the Plav; they 
do not include the open layer of loose hanging rootlets (see section I, 
РІ. 24). 
(2) ** Ueber diesem sehwimmenden dürren Rohr wüchst einesteils griines 
Schilf, das sich aus den horizontalen Hhizomen des Plaur entwickelt," 
etc., etc, 
The aquatic portion, or rhizome, of the reed cannot be called sterile, 
because the aerial portion is not separate from it but is its continuation, 
rhizome and aerial extremity forming one shoot (see pp. 246-248 and 
PI. 11). 
(3) “Аш unteren Teile des * Plaur’ gehen die Schilfrhizome in Füulnis 
über; da aber im Wasser nieht genügender Sauerstoff hierzu vorhanden 
* Pp. 225-224, op. cit. T Plaur — Plav. 
t in proof of the floatage of Plav, Dr. Antipa adduces the fishermen's huts built on Plav, 
which, because the Plav floats, are more or less habitable all the year round. He also cites 
the abundance of wild boar (Sus scrofa ferus, Ball) in the lower portion of the delta, around 
Sulina, Chilia, and Dranov, where Plav abounds, Where Plav is scarce, as in the upper 
portion of the delta, though the reed occurs abundantly as a thicket, wild boar are 
scarce. 
