In answer to a somewhat random LiveJournal challenge by Kaizoku Shojo (make H&W discuss a tree):
"I don't believe you."
"Nevertheless, I am correct, Watson."
"I doubt it."
"What, you don't think I know my plants?"
" 'Has no knowledge of practical gardening.' "
"I can't believe you still have that list memorised."
"You've never let a chance go by to throw it in my face, I should have it down by now. Besides, you're trying to change the subject."
"I'm not!"
"You are."
"I am not – I tell you I know exactly what it is."
"You're guessing."
"I never guess – shockingly destructive to the logical faculties."
"Yes, you've told me a thousand times. But I still say you're guessing."
Holmes's eyes gleamed.
"You're a gambler - would you like to wager on that?"
"With what?" I asked, ignoring (for now) the slur on my character.
"You buy the theatre tickets when we return from this walk, I choose the performance?"
"Done. I still say you're guessing – you can't possibly recognise this tree if you couldn't even identify Mrs. Hudson's tulips last spring!"
"You're adamant on that?"
"Quite. I'll go get an identification book and prove you wrong!"
"Don't bother," Holmes replied with a wicked smirk, gesturing with his stick to a placard I had not seen, laughing at my dismay.
"Silver birch. That's unfair, Holmes!"
"My dear Watson, you really must learn to control your betting."