POTSDAM, Germany (AP) — Wolfgang Bivour carefully emptied a basket of freshly collected mushrooms onto a forest floor covered with fallen autumn leaves. Brown-capped porcini and bay boletes lay beside slimy purple brittlegills and honey-colored armillaria — and, among them, the lethal green death caps. Bivour, one of Germany’s most famous fungi connoisseurs, described the different species just collected in an oak and beech forest on the outskirts of Potsdam in eastern Germany. Surrounding him