VEGETATION OF THE MARSH AND BOG 243 
latter is often quite aquatic in habit, with finely-cut 
submerged leaves and broader floating ones—S7zum lati- 
folium and 8. angustifolium (water-parsnips), Scrophu- 
laria aquatica (marsh-figwort), Veronica scutellata (marsh- 
speedwell), V. Beccabunga (brooklime), V. Anagallis 
(water-speedwell), Mentha aquatica (water-mint), Poly- 
gonum amphibium, P. Hydropiper, Rumex Hydrolapa- 
thum (great water-dock). 
The reed-swamp may be succeeded on its landward 
side by true marsh or woodland-swamp, or damp meadows 
may extend almost to the water’s edge. In the latter case, 
and also when a towing-path is present, the river-bank 
is occupied by a mixed assemblage of plants, dominated 
by sedges, grasses, and rushes. The roots or rhizomes of 
these plants are usually situated in saturated soil, but 
no part of the assimilating organs is under water. It is 
here that the annual marsh-plant finds a home (see list, 
p: 241). The most frequent perennials are: Thalictrum 
flavum (meadow-rue), Althea officinalis (marsh-mallow), 
Spirea Ulmaria (meadow-sweet), Lythrum Salicarva 
(purple loosestrife), several species of HL pilobium (willow- 
herbs)and Mentha (mints), Valeriana officinalis, Hupatorvwm 
cannabinum (hemp-agrimony), Senecio aquaticus (marsh- 
ragwort), Lysimachia vulgaris (yellow loosestrife), Lycopus 
europeus (gipsy-wort), Scutellaria galericulata (skull-cap), 
Stachys palustris (marsh-woundwort), Myosotis palustris 
(marsh forget-me-not), Symphytum officinale (comfrey), 
and isolated trees of willow, alder, and birch. 
The dominant plants of the reed-swamp possess sub- 
terranean creeping stems which tend to travel away from 
land. Humus collects at the base of the plants, and in 
lakes and ponds the bottom, through its accumulation, 
gradually rises. In this way a pond may be choked up 
and converted into a marsh. The danger is not so great 
in rivers, for the humus is carried away by the current, 
but even here the plants must be periodically removed 
to keep the water-way clear. 
2. Woodland or Bush-Swamp. 
The alder and willow, which are usually found sparingly 
in the reed-swamps, may become very numerous and 
form distinct associations along the margins of rivers ; 
or they may extend for a considerable distance landwards 
