52 VEGETATION OF THE PEAK DISTRICT [cH. 
a planted tree, it is locally abundant and succeeds well. First- 
year seedlings of sycamore are common ; and occasionally these 
grow up into trees. 
No species of lime is indigenous in the oak and birch woods 
with the possible exception of the small-leaved species (Tilia 
cordata=T. ulmifoia=T. parviflora); and even this is ex- 
tremely rare. The common lime (T. europaea = T. vulgaris) 
is never a woodland plant; and the broad-leaved lime 
(T. platyphylla = T. grandifolia) is not indigenous in Derby- 
shire. 
Ivy (Hedera Helix) is a constant and frequent associate in 
all the woods. 
The ling or heather (Calluna vulgaris) is confined to 
woods whose soil contains much acidic humus or peat, and 
to the more open parts of such woods. 
The bilberry (Vaccinium Myrtillus) occurs in somewhat 
similar situations to the heather, and usually grows with it; but 
it also thrives in more shady parts of the wood than that plant 
(see figure 7). The cowberry (V. Vitis-idaea) is local, but 
very abundant in some degenerate woods with a peaty soil, 
as in Longdendale, near Crowden railway station. 
The ash (Fraxinus excelsior) is, in the oak woods, almost 
limited to stream sides and swampy places. In the drier oak 
woods it 1s very rare. 
The elder (Sambucus nigra) is locally abundant in the 
lower woods, but rather uncommon at the higher altitudes. 
In places where the woods are disturbed and especially near 
villages, the plant frequently overruns the ground. 
The guelder rose (Viburnum Opulus) is, in all the damper 
woods, an occasional associate, and reaches comparatively high 
altitudes (about 318 m.). 
The honeysuckle (Lonicera Periclymenum) is abundant 
and general. This plant and the ivy are the only indigenous 
lianes of the north of England. 
