Buying stock does not withdraw the money from source-account

[Daniel Kraft]

Hi!

First of all:  Sorry for this - probably - very basic question, but I 
wasn't able to find a sufficient answer in the gnucash documentations.

I'm trying to buy some stock shares with gnucash (2.0.1) - if, for 
instance, I enter this transaction to the stock account:

100 shares, price 1$, from Assets:Bank

The stock account is updated correctly - I get 100 shares, and "Buy" 
gets a value of 100$.  However, in the Assets:Bank account, there isn't 
a number in either the Deposit nor the Credit column - therefore, I do 
not get any money credited from my bank account, while still getting my 
stock shares!

What am I doing or understanding wrong here?

Many thanks in advance!
Yours,
Daniel Kraft