Redmine

hi,
i'am novice at ruby on Rails framework. i'am trying to add a plugin for Redmin wich is a Rails application.
My problem:
i have this code in my html.erb file:
<%= form_tag :action => "sauver" >
<table>
< @types.each do |untype| >
<tr>
<td>
<= untype[:alertetype] >
</td>
<td>
<= collection_select(:tracker, :id, @trackers, :id, :name, options ={:prompt => "choisir un tracker"}) >
</td>
</tr>
< end %>

</table>

<%= submit_tag "valider" %>

i need to recover all values selected. When i use "params[:tracker][:id]" i have just one value posted.
Could you help me please.
Thank you in advance.
Cordially