Take a levels

Dear all,
How can I take a levels from a dataset.
For example,

data(iris)
x.iris <- iris[,1:4]
y.iris <- iris[,5]

y.iris

  [1] setosa     setosa     setosa     setosa     setosa     setosa
  [7] setosa     setosa     setosa     setosa     setosa     setosa
....
[139] virginica  virginica  virginica  virginica  virginica  virginica
[145] virginica  virginica  virginica  virginica  virginica  virginica
Levels: setosa versicolor virginica

I want like,
y.iris level are,
[] setosa versicolor virginica