Pitchers

Is the formation of upper pitchers a gradual process, each pitcher changing little by little?

[Tony Paroubek]

Usually yes. The plant will go through a series of pitchers that become more and more upper pitcher in shape and form. Cutting can go right to producing upper pitchers if the plant the cutting is taken from was producing upper pitchers already.
Tony

[Tony Paroubek]

hmm rereading that and I don't think I explained that well...

Seedlings will produce lower pitchers for a long while until they hit a certain size. Once they start the process of forming upper pitchers they will go through that transformation range where pitchers vary somewhere in between upper and lower shape. You will often see these pitchers termed intermediate.
Tony

I saw a pic of a cool rafflesiana, intermediate pitcher. It looke like an upper, but with wings. Can't wait till I get my Bau, giant form!