THE ALDER BUCKTHORN— continued. 
bark,” the inner bark of R. Purshianus De Candolle, a native of the Pacific slope of 
North America, more especially Oregon. 
The name Buckthorn is merely an early mistranslation of the German Buxdorn, 
i.e. the thorn-bearing Box ; but Rhamnus , or rather its Greek equivalent pdfxvos, 
rhamnos, dates from Theophrastus. Our two British species belong to distinct 
Sub-genera or Sections. In the one, Eurhamnus, to which R. calharticus belongs, 
the flowers are usually tetramerous and dioecious : in the other, Frangula, they are 
pentamerous and perfect. While R. calharticus is a stiff, much-branched, spinous 
shrub, growing upon calcareous soil, R. Frangula is unarmed, has a far looser habit 
of growth, with slender branches, and flourishes on clay or wet alluvial soils. 
The name Frangula , used by Matthiolus, is derived from the Latin frango , I 
break, the twigs being considered brittle ; while, growing, as it often does, side by • 
side with the Alder, slightly resembling it in leaf and at once distinguished by its 
berries, it was also known as Alnus nigra baccifera or Black Berry-bearing Alder, Aller, or, 
in Lancashire, Owler. Its soft, spongy, yellowish wood is largely used, under the 
name of Black Dogwood, in the manufacture of gunpowder charcoal. The leaves are 
the chief food of the caterpillar of the beautiful Brimstone Butterfly ( Gonepteryx 
rhamni). The twigs are slightly angular, tinged with a violet colour, marked with 
small half-moon-shaped leaf-scars, each with three terminations of veins, and with 
numerous whitish lenticels or cork-warts, and bearing small grey hairy buds without 
bud-scales. The small round berries only contain two stones, and turn from a 
polished vivid green to bright red and ultimately to black, whilst those ot 
R. calharticus pass at once from green to black and contain four stones. 
