How we cite our quotes: (line)
Quote #1
But when the bath was filled we found a fur, (line 18)
Here's the first blotch on their otherwise successful berry hunt. The boys are probably as proud as peacocks that they've picked enough berries to fill a whole tub and now they're finding out that the beautiful fruit's about to spoil. Just around the corner of the height of satisfaction is disappointment.
Quote #2
A rat-grey fungus, glutting on our cache. (line 19)
You can almost hear the anger in his voice. It's not a cloud-gray fungus, it's "rat-grey." Rats just about never mean anything good or positive (unless you're a hungry snake). The rat seems to be robbing these boys of something, ushering in their disappointment.
Quote #3
The juice was stinking too. (line 20)
So, the berries are spoiled and there isn't even a consolation in the juice; that's spoiled too. "Stinking" works like "rat" does in the previous line. It's used as an insult in our everyday language – "stinking liar," "stinking jerk," "I hate eating stinking Corn Flakes every morning." The speaker feels disappointed and hurt, and the language of the poem reflects that.