258 MISS MARIETTA PALLIS ON THE 
living aerial portions of the shoots weigh roughly 15 lbs. (6:8 kilogs.) 
(see p. 265), and probably much more; from which it also follows that 
the reed-rhizome is renewed completely at least once in three years. 
Closed Reed-swamp. 
Closed reed-swamp develops from open reed-swamp automatically, as 
explained, and in time becomes Plav. It is of many degrees of maturity, 
and therefore is composed of reed-tussocks of many sizes. 
Thus in one spot all the reed-stools are rooted, and their tops are therefore 
well under water, and in another spot they are, owing to the growth of 
accompanying plants, almost level with the surface of the water. In this 
way in some places where land-plants are already settled on the stools the 
reed-swamp has the appearance of a secure land-surface, though a slight 
pressure suffices to push the stools under water *. 
Much soil is held both by individual tussocks and by closely growing 
assemblages of tussocks. Three layers of soil (fluvio-lacustrine ooze) are 
distinguishable, just as in Play. The colour of the soil is greenish-grey and 
lighter than that of Play, and the top layer of black soil contributed by the 
land-plants rooted in some of the tussocks is less thick than in Plav, and 
sometimes absent, as is to be expected since the land-plants are new-comers. 
At the closed reed-swamp stage fluvio-lacustrine ooze usually covers the sand 
bottom on which the reed originally established itself. 
In old closed reed-swamp a considerable number of the basal connecting 
rhizomes are dead, hence the stools are often attached to each other more 
securely above than below. The lattice of branches, also, as already explained 
(see р. 250), is more open below and there are no water-roots; thus the 
basal portions of the reed do not hold soil, and circulation of the water 
proceeds more readily below than above. The reed, in fact, tends to become 
less secure as regards attachment to the bottom the older it gets, and detach- 
ment apparently follows quite naturally at a more or less fixed time : first, 
because of the death of the basal rhizomes, and secondly, because the 
tussock increases in size, and above also in solidity ; hence the water 
circulates readily below but exerts pressure against the solid upper portion 
of the stool. In other words the greater the base of the stools the greater the 
* This stage of swamp -is quite well marked and has received the name of Bouharnik 
from the fishermen—the significance of which I have not been able to learn. It apparently 
has some jocular meaning connected with the ease with which it is possible to founder in 
trying to step from stool to stool. 
The Russian fishermen distinguish other stages of reed-swamp also—for instance, Ritkovina 
Riceavina, Ritkovo—open reed-swamp through which a lodka (boat) can be forced ; Triceaba, 
closed reed-swamp through which a lodka cannot pass; Opowshena, reed-swamp formed of 
large tussocks through which a lodka can thread its way. 
