124 C. E. MossffW. M. Rankin and A. G. Tansley. 
the country, have not as yet been studied in any detail. Like those 
already referred to, they are found only on very wet soils, with the 
water level at or very near the surface, fringing the flat banks of 
slowly running streams, or round ponds and on springy ground 
within woods belonging to one of the other principal series. The 
dominant trees are the alder (AInns rotundifolia), the sallows ( Salix 
cnprcca and S. cinerea), the crack willow (S. fragilis), more rarely the 
white willow (S. alba), and the osier (S. viminalis). In the upland 
portions of the northern Pennines, 5. nigricans and S. phylicifolia 
occur. The ash ( Fraxinus excelsior) is also often abundant in these 
thickets. 
The thickets are very frequently coppiced along with the drier 
woods of different types which often adjoin them and into which 
they may gradually pass. In the marshy meadows along stream- 
sides, i.e., in very much the situations of the corresponding natural 
associations, planted coppices of alder or ash are often met with. 
“ Osier beds ” are similar plantations on wet clayey or alluvial soils, 
but apparently rarely on peat. 
The ground vegetation of these thickets is characteristic. The 
great hummocks of Carex paniculata are a striking feature. These 
occur also in the Norfolk “carrs,” together with the smaller tufts of 
C. paradoxa. The tall and graceful Carex pendula and some others of 
the larger sedges are also found. Scirpus sylvaticus, (Enanthe crocata, 
Cardamine jlexuosa, C. amara, Caltha palustris, Mentha spp., Epilo- 
binin hirsutnm. Nasturtium officinale, Myosotis palustris, Chryso- 
splenium oppositifolium. Iris Pseudacorus, Valeriana sambucifolia, 
Scrophularia aquatica, Spircca Ulmaria, Aira ccespitosa, Phragmites 
communis, and Molinia ccerulea are other characteristic species of 
this association. Rarer but equally typical are the following :— 
Carex Pseudo-cyperus, Phalaris arundinacea, Calamagrostis Epigeios, 
C. lanceolata, Lastrcea spinulosa, L. Thelypteris, Osmunda regalis, 
and Equisetum sylvaticum. 
II.— Oak and Birch Series. 
The woods of this series are found on all the “ siliceous ” ( i.e ., 
non-calcareous) soils, ranging from the stiffest clays, through the 
various loams, to the sands and gravels and the soils derived from 
sandstones of various ages, as well as on the soils derived from the 
older non calcareous rocks, such as grits, mudstones, shales, and 
various acidic igneous rocks, 
