I believe that all the Xanthosomas that you see in Florida are
Sagittifoliums. But the plant that Eduardo looked at was a robustum.
Here are the pics of the plant he saw that day. Also here is a link to
the plants that are grown all over Florida. You can tell the spath is
Yellow to off white on the Sagittifoliums and white to pink on the
robustum. Telling the difference from atroverins from robustum seems
fairly hard. Atroverins tends to have darker bluish green leaves. The
new stems come out a dark color and lighten up to the bluish green color
the flower is about the same a blue green spath. As for Robustum the
stems tend to keep a white dusting.
Eduardo let me know if this looks right to you??