Hemi-epiphytism represents an evolutionarily important yet poorly understood growth habit in ferns. Anatomy and ontogeny related to hemi-epiphytism in the fern Vandenboschia collariata (Hymenophyllaceae) were investigated at La Selva Biological Station, Costa Rica. Multiple specimens representing all stages of gametophyte and sporophyte growth were observed in the field, collected, and examined in the laboratory. Cross sections of sporophyte roots and stems were made by hand, and examined using light microscopy. Sporophytes were found to initiate growth on the base of trees up to ca. 25 cm above the ground. Two types of stems were produced: 1) a short stem that produces crowded roots, and 2) one or more climbing stems that branch from the short stem, climb up the trunk, and produce distant leaves but no roots. This study presents the first description of gametophytes in V. collariata and clarifies ontogeny and anatomy related to the hemi-epiphytic growth habit in ferns.