significance of newline in io?

working through "7 languages in 7 weeks", I noticed something interesting.
This method definition me an error when invoking:
Object ancestors := method(
    prototype := self proto
    if (prototype != Object,
        writeln("Slots of ",prototype type,"\n-------")
        prototype slotNames foreach(slotName, writeln(slotName))
        writeln prototype ancestors))

Whereas, this definition does not:

Object ancestors := method(
    prototype := self proto
    if (prototype != Object,
        writeln("Slots of ",prototype type,"\n-------")
        prototype slotNames foreach(slotName, writeln(slotName))
        writeln
        prototype ancestors))

the only difference here is the newline after "writeln". what is the
significance of the newline in the language? am I missing something in the
docs?

thanks for your help!

--paul