Exquisite arithmetic. (Upon discovering the secret of the pine)

Tornado rage has wrenched these woods awry. The silver birch hangs ravished of her hair, Spent arms akimbo in exhausted air. Yet in this wrack I marvel to descry The pine as yet untroubled, and ask why, By what caprice the winds meant to forswear Their wrath, or what admonished them to spare This Gothic spire that points beyond the sky. I peer within, and in its deep I see Two trees -- two trees athwart a dart of sun -- Two trees embraced in wedded entity. Oh strange that one plus one should equal one -- That two slim shafts equate one valid tree -- What exquisite arithmetic is here begun!