Andy, what is the common name of the Ficus capensis? I am familiar with Carpobrotus deliciosus which is a succulent, and which has the common name of Sour Fig ... and the fruits are used for jam. But I've never heard of Ficus capensis ... perhaps one of those rename tricks the botanists have been doing ? Please let us know, you have piqued my interest and your post has been sitting all lonely up there so give us more info about the plant's habit or other names, and let's see who else can contribute some info. D

Sorry, I should have gone read Una Van der Spuy's "South African Shrubs and Trees for the Garden" before i responded above ... now i know that it is a wild fig tree which can grow to 70 ft tall, but usually attains about 40 feet. Una states that "it is a spreading deciduous or evergreen tree with a thick bole and spreading roots, and it should therefore not be planted near buildings or drains." Also "the fruits are round, approximately 2-3 cm in diameter, but not good for eating."
Unfortunately Una says nothing about the seeds. Perhaps you can get information on this aspect from the web site of the South African National Botanical Institute? Also try PlantzAfrica.com . D