With the current way "transactions" are defined in the whitepaper I do not see that it is possible for contracts to send transactions but only responses to messages:
"Messages" in Ethereum are somewhat similar to “transactions” in Bitcoin, but with three important differences. First, an Ethereum message can be created either by an external entity or a contract, whereas a Bitcoin transaction can only be created externally. Second, there is an explicit option for Ethereum messages to contain data. Finally, the recipient of an Ethereum message, if it is a contract account, has the option to return a response; this means that Ethereum messages also encompass the concept of functions.
The term "transaction" is used in Ethereum to refer to the signed data package that stores a message to be sent from an externally owned account.
This would mean that contracts that send ether would not do this via "transactions" but "messages", the only difference there being that the former is signed whereas the latter is not. Correct?