290 ON THE STRUCTURE AND HISTORY OF PLAY. 
the Polystichum fronds about 1-2 m. (about 4 feet). А little Hypnum and Epipactus 
palustris, Crantz, were present. The molluse Dreissena polymorpha, Pall., was attached to 
the reed-rhizomes forming the edge of the island. 
SECTION Ш. 
“Fixed Play " of Phragmites communis var. В. flavescens, Gren. & Godr. (see page 259). 
The section was made on Sept. 19th, 1913, at the edge of the grind of Rosulet. The depth 
of water covering this “ fixed Plav” was about 0'75 m. (about 2 feet 6 inches) on Sept. 28th. 
The thickness of the Plav is about 1:35 m. (about 4 feet 6 inches). This Plav is quite 
uniform in structure; it consists of densely packed reed-rhizomes, and the soil throughout 
is a line and only slightly organic ooze (shown by the single light shade of the diagram). 
The depth of the sand, measured from the surface of the water, on Sept. 28th, was about 
2] m. (about 7 feet). 
The reed here was ‘ shitka” or slender, and measured about 2:2 m. (about 7 feet 
5 inches), from the surface of the Plav, and the inflorescence measures about 15 em. x 8 em. 
(6x3 inches), The accompanying plants are a few aquatics, i. e. Nymphea alba, Linn., Sium 
lancifolium, Bieb., Sium latifolium, Linn., Lemna trisula, Linn., and L. minor, Linn., 
Stratiotes Aloides, Linn., and Hydrocharis Morsus-rane, Linn. 
SECTION IV. 
Reed-Fen (Phragmites communis, Trin.), Section made on April 23rd, 1914, in the 
vicinity of Sutton Broad Laboratory on the River Ant, Norfolk. The top, or contemporary, 
fen-layer is about 1 m, (about 3 feet 3 inches) in thickness. The depth to the sand is 
about 5/2 т, (about 17 feet), The fen-layer consists of two layers: the top one, about 0:55 m. 
(about 1 foot 10 inches) in thickness, is almost exclusively living reed-rhizome and 
branched roots, and the lower layer mostly dead rhizomes and long mud-roots, The soil 
throughout the section is similar to the eye with the exception of the top soil, which is a 
little darker. The organie content of this fluvio-lacustrine ooze was estimated for me at 
Rothamsted. The loss on ignition (organic matter) was 41:76 рег cent. А similar ooze 
covers the bottom of Barton Broad near the Herons’ Carr ; its loss on ignition was 40:23 
per cent. The depth from the surface of the fen to the basal sand-bed (often coarse sand 
with a few flints) is in general far greater than in the delta. The greatest depth to the 
“hards” so far reached in the Broads was 31 feet (944 m.) in Salhouse Broad on July 27th, 
1912*, In the delta, even at high water, I have only in a few places reached 3 m. (10 feet). 
The length of the reed from the surface of the fen is about 1:8 m. (6 feet). "The 
inflorescence measures about 25 x 12 em. (about 10x 5 inches), 
PLATE 25. 
Dr. Antipa’s Mar of the DELTA OF THE DANUBE. 
* The boring tool used on that occasion was designed by Mr. Horace Darwin, Е. R.S., 
of the Cambridge Scientific Instrument Company, in conjunction with Mr, С. Lack. 
