Wegener's hypothesis was his belief in continental drift and the significance of the fossil glossopteris. Glossopteris has been an important consituent of coal deposits and partly became known from these deposits. It was a large seed fern reaching up to 30m high. It occurs on various southern continents like South America, Antarctica, New Zealand, and Africa and could not have been transported by ocean currents between these continents. Therefore it points to these different continents at one time being joined and in that way allowing for the spread of the glossopteris.