Merging similar attributes with XSLT

I have one XML-File wich is structured like this:

  <forms>
     <f form="AGAtam"><na><acc/><sg/><mas/></na><s stem="AGAta"/><m meaning="slayer, killer"/>    
     </f>
     <f form="Adatte"><s stem=""/><m meaning="he seizes, carries away"/></f>
     <f form="Adatte"><new/><s stem=""/><m meaning="he seizes, carries away, takes to a different place"/></f>
     </forms>

What I want now is an XSLT-template wich replaces all the nodes wich do not have a new-tag as a child with the node that have such a tag, while keeping all other childs/attributes the same. In this case it would mean to replace the node in line 4 with the one in line 5. Any help is greatly apprechiated!