National Geographic : 1925 May
MARVELS OF FERN LIFE Fronds slightly reduced Painting by E. J. Geske ADDER'S-TONGUE (Ophioglossum vulgatum) AND CLIMBING FERN (Lygodium palmatum) The Adder's-tongue (at right) is allied to the Rattlesnake Fern, but has a simple entire sterile blade and the sporangia fused in a tongue-like stalked spike, as shown in the upper detailed figure. The Climbing Fern (at left) is the only one of its kind native to the United States. The detail at left shows the overlapping scales of a fertile segment. A single sporangium, with hard elastic cap, is shown in the middle, magnified 50 times.