National Geographic : 1925 May
MARVELS OF FERN LIFE One-half natural size natural size © Painting by E. J . Geske , S CHRISTMAS FERN (Polystichum acrostichoides) One of our : best known species, with thick, evergreen fronds, much sold with cut flowers under the name Dagger Fern. Some of the fronds have contracted tips, with close-set sori covering the under side of the pinnae. A sorus, with shriveling parasol-like indusium, is shown at bottom; a ripe sporangium above.