268 MISS MARIETTA PALLIS ON THE 
the most obvious cause of fluctuating variation in length of the aerial shoots 
of one single reed-thicket. The reed-rhizome is often compound to the sixth 
degree, and, in general, the highest compound is the shortest branch, not 
merely as a whole, but even as regards its aerial portion (see р. 250). А great 
deal of the variation in size of the aerial shoots of one reed-thicket—for 
example, within a thicket of giant-reed, tall-slender reed, etc.—is therefore 
more apparent than real; and could real fluctuating variation be eliminated, 
the difference in length of the tallest and shortest aerial portions of the 
reed-shoots of one thicket would express the degrees of branching—which 
I have never found to be more than to the sixth degree—existing together at 
any one of the different periods of growth of the major individual. The size 
of each fresh generation of shoot is, in fact, closely co-related with the size of 
the generation of shoots preceding it, just as the sizes of the shoots of one 
generation are co-related as indicated above. The size of the shoot is a more 
or less exact measure of the absolute age or period of growth of the reed 
major unit. 
The variation in the size of the shoots in any one thicket is much smaller 
than that obtaining between tall-stout and short-slender reed. The magnitude 
of the latter variation expresses, I believe, the total compoundness of branching 
which the reed major unit attains; it is the expression of the very high 
degree of branching of the reed with reference to its original dead and 
vanished basal rhizome. The branching of the reed is indeed comparable 
to that of the tree, but its trunk and its lower branches do not, as in the 
tree, persist throughout its life. Nevertheless its first shoot and its last are 
morphologically co-related. 
The Major Individual. 
The recognition of stout and slender reed as younger and older reed 
respectively, makes it possible at a glance to distinguish the old Plavs, and 
the older portions of a Plav; thus the areas covered by reed of different 
ages can be measured, and, further, it becomes evident that Plav often arises 
in comparatively small pieces. I took a few very rough measurements with 
a tape-measure, and also by pacing, and I do not think that it is usual for 
Plav formed of stout reed—i.e. newly-risen Plav—to be more than 50 squared 
metres (about 55 yards across) in area. If the thickets of different-sized reed 
which together form the larger Plavs became detached on separate occasions, 
the large Plavs must be regarded as compound structures. 
The question arises: are the above data of use in establishing the major 
unit? Is the major unit a whole Plav consisting perhaps of several thickets 
formed of different-sized reed, or is it asingle thicket ? This question cannot 
be answered now. Ifa Plav consisting of several thickets be assumed to be 
the major unit, the sharply-marked difference in size of the reed of contiguous 
thickets demands explanation, since a gradation in size coincident with the 
