376 МП. К. S. ADAMSON : AN ECOLOGICAL STUDY 
1. (Ash) Oak-Hazel Woods.—This is the dominant kind. of woodland on 
the ealeareous Boulder Clay, both on that over Gault or Greensand in 
Western Cambs., and also on that above the Chalk in the S.E. of the county. 
The woods existing at the present day are usually small and rather isolated 
patches, often occurring on the summits of ridges. There is considerable 
evidence that adjacent patches, in some cases at any rate, are the last 
remnants of much larger woodland areas which have been more or less 
completely cleared for agricultural purposes. That woodland vegetation is 
the natural type on the intervening land is seen clearly in parts of Western 
Cambridgeshire, where pastures which have been allowed to run wild for 
some years are becoming colonized by shrubs, which form a more or less 
dense serub ; this scrub is mostly composed of Hawthorns, springing from the 
surrounding hedges, but in older stages there appear also Hazel, Oak, 
Maple, and Ash. 
All the Ash (Oak- Hazel) woods in the county are periodically coppiced and 
allowed to regenerate naturally. All of them are of the same general type as 
the calcareous clay part of Gamlingay Wood. 
Those on Boulder Clay over Chalk, as Borley Wood and Balsham Wood, 
have the drier types of ground society especially developed ; Mercurialis 
perennis here forms extensive pure sheets. On the other hand, in Hayley 
Wood and Eversden Wood in West Cambs., the wetter Spirea Ulnaria 
Societies are the most prominent. In Hayley Wood and Kingston Wood, 
Oxlips occur to the complete exclusion of the Primrose. 
2. Oak Woods are not very extensively developed in the county; two of 
these oecur on the Greensand in the Gamlingay district. White Wood has a 
deep sandy soil : И is a mixture of Quercus Robur and Q. sessiliflora. The 
ground flora is of а drier more healthy type than the dry oak wood part of 
Gamlingay Wood, with Deschampsia flexuosa very prominent. Great Ива 
Wood, also on the Greensand, in so far as it is natural at all, has а very 
healthy type of flora, with Calluna vulgaris and Deschampsia flexuosa dominant. 
Neither of these woods is of quite the same type as the loam area in 
Gamlingay Wood. 
3. Beech Woods, apparently natural, occur in small quantity on the Chalk. 
Effect of Environment on the Structure of Plants * t f$. 
Some anatomical investigations have been carried out on some of the more 
abundant species in the wood, from material collected in different conditions 
of growth, with a view of ascertaining how far structural adaptation was 
connected with the power of adjustment to a large range of light-intensities. 
The two species which show the greatest amount of structural changes are 
Cirewa lutetiana and Rumev viridis, both of which flourish in light-intensities 
в Woodhead, 1906, р. 368, Т Stahl, 1880, 1883. + Pick, 1832, $ Nordhausen, 1903, 
+ 
