There are two magnolias in the Park, a pink white magnolia in the northwest triangle and a sweetbay magnolia in the southeast triangle. See Wikipedia entry for the sweetbay here.
The sweetbay magnolia is also called simply sweetbay. It was the first magnolia to be scientifically described, and is the type species of the genus Magnolia. Since Magnolia is also the type genus of all flowering plants, this species can be seen to typify all flowering plants.
The sweetbay magnolia in front of the black pine in the southeast triangle in June, looking west
Sweetbay magnolia factoids:
Evergreen in Philadelphia (Zone 7: see below) but can be deciduous further north
June 8, first flower on the sweetbay magnolia.
The sweetbay flowers almost two months after the pink white magnolia in the northwest triangle, and the evanescent flowers are completely gone in a few days.
Unripe fruit on the sweetbay magnolia in July being enjoyed by a swarm of insects
These fruits will ripen to red, as seen below, and will be quickly eaten by animals.
Philadelphia is in Zone 7.
Botany 101 Bonus
There are other food sources in July besides the sweetbay magnolia being enjoyed by insects. The photo below was taken in late July and show a "baker's dozen" for the animals and insects.
Thirteen seed and fruit sources of food in late July.
The young black pine cones in the center are eaten while still on the tree. The seeds float to the ground from the older woodier cones and are eaten on the ground. Seeds are exposed in the redbud and golden rain tree pods. The "berries" toward the top of the yellow cypress are really cones.