list of curves in do-loop



Thanks a lot for you tip on plotting severeal curves with a loop at
http://www.math.utexas.edu/pipermail/maxima/2006/002796.html

f(n) := block(
    [curves : [], i],
    for i:1 thru n do curves : cons(x^i, curves),
    plot2d(curves, [x,-1,1])
)$

It helped me already a lot, but I have a question in order to understand 
what's going on.

Why the statement with i in:

 [curves : [], i], 

it works also with just: 

 curves : [], 

which creates an empty list. What is it good for to add the ", i]" ?

many thanks in advance,

Gerhard

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