An object of class cross. See
read.cross for details.
...
Ignored at this point.
Value
A short warning message is printed, and then the function
summary.cross is called, and so a summary of the QTL
object is printed, and the summary is returned.
The main reason for including this function is that these
"cross" objects are generally quite large and complex, and one
often unintentionally types their name and gets the entire thing
printed out. The inclusion of this function makes typing the name of
a "cross" object result in just the summary being printed.