INTRODUCTION 7 
leaves on the branches through the winter, or at least 
until a severe frost followed by a thaw brings them 
down. ‘The buds, leaves, and flowers are all much 
attacked by gall-forming insects, many different kinds 
being found on one and the same tree. 
Itis not until the oak is from sixty toa hundred years 
old that good seeds are obtained from it. Oaks will bear 
acorns earlier than this, but they are apt to be barren. 
A curious fact is the tendency to produce large numbers of 
acorns in a given favourable autumn, and then to bear 
none, or very few, for three or four years or even longer. 
The twisted, ‘gnarled’ character of old oaks is well 
known, and the remarkably crooked branches are very 
conspicuous in advanced age and in winter (Plate IT.). 
The bark is also very rugged in the case of ancient trees, 
the natural inequalities due to fissures, &c., being often 
supplemented by the formation of ‘ burrs.’ 
A not inconsiderable tendency to variation is shown 
by the oak, and foresters distinguish two sub-species and 
several varieties of what we regard (adopting the opinion 
of English systematic botanists) as the single species 
Quercus Robur. 
Besides forms with less spreading crowns, the species 
is frequently broken up into two—Q. pedunculata, with 
the female flowers in rather more lax spikes, and the 
acorns on short stalks, the leaves sessile or nearly so, 
and not hairy when young; and Q. sessiliflora, with 
more crowded sessile female flowers, and leaves on 
short petioles and apt to be hairy. Other minute 
