As part of a joint NASA-USFS project, about 400 to 500 tree seeds from Douglas fir, loblolly pine, redwood, American sycamore, and sweetgum trees were stored in small containers in Stuart Roosa's PPK during the Apollo 14 mission. Upon his return to Earth, many of the seeds were germinated. Their seedlings were planted throughout the United States, Japan, Brazil, and Switzerland, becoming known as "Moon trees". For the Apollo 17 mission, the PPK was replaced with the astronaut preference kit (APK).