137 

 NOTES AND COMMENTS. 



BRITISH OAKS. — QUERCUS SESSILIFLORA, 



To thQ numerous botanists who have experienced the 

 difficulty of distinguishing our British Oaks, the article by Dr. 

 C. E. Moss in the January and February issues of the ' Journal 

 of Botany ' will be welcome. Of the two native species, 

 QuercHs scssiliflora and Q. Rohur { = Q. pedunculata) , the former 

 is best distinguished by the presence of stellate {i.e. branched) 

 hairs on the under surface of the leaf. These hairs may easily 

 be seen by means of a lens magnifying lo or 12 diameters, and 

 they are very conspicuous on some forms of the tree. They 

 may be distinguished at any time of the year and even on 

 fallen dead leaves and in old herbarium specimens. On the 

 rocks of the Millstone Grit and Coal-Measure series of the 

 Pennines Q. sessiliflora is the dominant tree in the woods 

 below 1000 feet. Above this altitude the tree occurs rarely 

 up to 1200 feet. 



OUERCUS ROBUR, 



This tree, often quoted under the name Q. pedunculata 

 Elish., may always be identified by the presence of two com- 

 pletely reflexed auricles at the base of the blade and by the 

 absence of branched hairs. It is characteristic of deep soils, 

 while (). sessiliflora generally occurs on shallow soils ; but both 

 species occur side by side in some woods on deep sandy or 

 gravelly soils. Generally, however, they characterise distinct 

 regions. In East Cheshire the Q. Rohur region ceases at about 

 600 feet, in West Yorkshire this region does not reach even 

 such a moderately low altitude. The tree is planted on the 

 Pennines up to iioo feet. 



QuERCUS ROBUR X SESSILIFLORA. 



The two preceding species form a natural and fertile hybrid 

 whose occurrence in Britain is widespread. The first British 

 record seems to be that in the ' Naturalist ' for March 1909 

 (p. 113). The hybrid oak has recently been observed in 

 several vice-counties including Chester, South and West Lan- 

 caster, North-East, South- West, and Mid-West Yorkshire, and 

 Westmorland ; and herbarium specimens indicate its occur- 

 rence in Derbyshire and elsewhere. The hybrid is easilv 

 distinguished by the presence of both branched hairs and 

 reflexed auricles. This Oak is not Q, intermedia of D. Don., 



1910 Apl. I. ^ 



