48 SCIENCE PROGRESS 



In the same journal for March, W. E. Nicholson records the 

 liverwort Southbya nigrella as a British plant from Portland. 



Ecology. — ^Adamson in a lengthy paper in the Journ. of 

 Ecology (vol. ix, No. 2) deals with the woodlands of Ditcham 

 Park in Hampshire, an area with a rainfall of about 40 in. In 

 the Beechwoods the soil varies in depth from very shallow to 

 nearly 16 in. on the western slopes, where also the humus 

 is deeper. The rooting depths of the ground flora are mostly 

 4-5 in. or 5-9 in. on the western slopes. The soil reaction mostly 

 lies between p.H. 7-5 and p.H. 8-5, the higher values being 

 associated with the Mercurialis perennis, Sanicala europcea, 

 etc., whilst the lower alkalinity is met with where Scilla nutans 

 is associated with the Dog's Mercury. 



The flora of the five areas studied shows an aggregate of 

 28 trees and shrubs of which Fraxinus excelsior, Acer conipestre, 

 Cornus sanguinea, Euonymus europceus, Sambucus nigra^ and 

 Sorbus aria are the most frequent. Birch is absent, whilst 

 Oak is very rare. 93 vascular plants and 52 Bryophytes com- 

 prise the ground flora. Large areas are more or less bare, 

 but the chief species are Sanicala europcea, Mercurialis perennis, 

 Viola sylvesiris, Ajuga reptans, and Euphorbia ainygdaloides. 



The light intensity varies from 17*5-63 per cent, during 

 the light phase and from 0-98-5-22 per cent, during the shade 

 phase. 



The humidity during the periods of observation was between 

 53 and 100 per cent. Calcicolous coppice occupying areas of 

 felled Beechwood is characterised by an absence of any humus 

 layer, and of course a large number of species (trees and shrubs, 

 33 ground flora, 136 vascular plants, and 39 Bryophytes). 



The development of a Cornus scrub on a felled area is de- 

 scribed, and after six years 73 species were found, which 

 increased the following year to 96 and after 13 years to 

 90 spp. 



The Oak Hazel woods exhibit a ground flora in which Mer- 

 curialis perennis, Circcea lutetiana, and Teucrium scorodonia are 

 the most important members. The woods of this type fur- 

 nished 32 woody species, 209 herbaceous species, and 43 

 Bryophytes. 



Salisbury in the same journal treats of the stratification 

 of the soil with especial reference to the hydrogen ion 

 concentration in woodlands. Graphs of typical examples from 

 a large mass of data are furnished showing the marked decrease 

 in acidity that is often exhibited as one passes from the 

 surface downwards. This is an outcome of progressive leach- 

 ing and the gradual accumulation of humus in the surface layers 

 and on the surface of undisturbed soils. 



The view is advanced that this tendency results in an 



