370 MR. В. 5. ADAMSON : АХ ECOLOGICAL STUDY 
Hypericum tetrapterum, Lychnis Flos-eueuli, with Juncus lamprocarpus and 
Galium palustre in the centre. Others have a thick growth of Lythrum 
Sulicaria. In those with more moisture, the zones round the edges have the 
above species, while in the centre are Lysimachia Хиттшана, Ranunculus 
repens, and (alium palustre, with sometimes also Callitriche stagnalis, and 
Surhynchium rusciforme in one case. 
Those with true aquatic vegetation are restricted to two examples. Опе, 
the larger and deeper, ix in an open area. Hound the edge is а dense growth 
of Spirea Ulmaria and Angelica sylvestris, while immediately over the 
water's edge are Lysimachia Nummularia, Carex remota, C. vulpina, Juncus 
lampocarpus, and J. effusus. In the water of this pool, which is about 2 ft. 
deep in the centre, are large quantities of Chara sp., Ranunculus Drouetit, 
Hypnum aduncum, and green Algw. A few plants of Alisma Plantago and 
Sparganium ramosum also occur in this pond and also Glyceria aquatica (one 
plant). The second pond is in a deeply-shaded area: the surrounding vegeta- 
tion is the Shade Spirwa Ulmaria Society. In this case there are no fringing 
plants, but this is probably due to the fact that the banks are very steep. In 
the water are Callitriche stagnalis and Lemna minor, with Algæ. The water 
in these ponds is neutral to test-paper. 
PLANT SOCIETIES OF THE LOAM. 
The conditions affecting the ground flora here are rather different from 
those on the calcareous clay. The shrubs are thinly scattered or absent. This 
allows a much greater percentage of light to penetrate to the ground flora ; in 
fact, the light at the summit of this is not reduced below 0'3 except im- 
mediately below trees and bushes. Correlated with this is a much greater 
rate of evaporation ; the rate here also increases regularly with the height 
above the ground. The evaporation rate just clear of the ground flora is 
"ther more than E, in the permanent series, but not so great as Е”. The 
rate on the ground varies with the plants present ; when the full growth of 
Pteris aquilina occurs the rate beneath it is very small, the smallest recorded 
in the wood. But in spring. or when Pteris is absent, the rate is greater 
than in other parts of the wood. Thus for June to July the proportion in a 
part dominated by Molens mollis was :— 
Hàoleus mollis Soe. : Merenrialis Soc. : Spirra Soc. 
= 100 : 85:4 : 12 
The figures are for rather open parts on the caleareous clay. 
Another difference is the soil-moisture : in winter this is nearly as high a 
percentage ах Гог the calcareous clay, but it falls steadily through the spring 
* See above under ** Myaporation.” 
