Class (Plantae): Gnetopsida

Gnetopsida only consist of three genera, which are highly variable in their overall morphology and distribution. Perhaps the strangest plant on the planet is the welwitschia (Welwitschia mirabilis). It is considered a living fossil with a very strange growth habit. Following germination, the two cotyledons (seed leaves) give rise to two true leaves. Those leaves continue to grow throughout the life of the plant reaching upwards of 6 meters, and no new leaves are produced.

Reference: The Biology Primer