Notes on Micronesian Pteridophyta, III. Ophioglossum nudicaule in the Caroline Islands

Abstract

The rather saline environment of a coral atoll seems scarcely the place to look for a terrestrial Ophioglossum, and none has heretofore been reported from any atoll to the best of my knowledge. Ophioglossum pendulum L., an epiphytic species, has been found on Mili, Namorik, Ebon, and Jaluit atolls, in the southern Marshall Islands (St. John, Occ. Pap. Bishop Mus. 17: 177-182. 1943; Stone, Micronesica 1: 155. 1964; Fosberg & Sachet, Atoll Res. Bull. 92: 2. 1962). Hence, my astonishment was great when I spotted a small colony of one of these diminutive plants along a path in a coconut plantation just outside a village while I was hurrying to be picked up by a small boat on Fassarai Islet, Ulithi Atoll, August 17, 1965. I stopped, verified the observation, and hastily collected a few specimens (Fosberg & Evans 47400, MICH, UH, US). Two relatively recent papers treat the genus Ophioglossum in the Pacific region (Clausen, Mem. Torrey Bot. Club. 19(2): 1-177. 1938; Wieffering, Blumea 12: 321-337. 1964). The viewpoints and characters used by these authors are very different, and the keys of neither of them work very readily on the Ulithi specimens. However, after studying very carefully the material and the descriptions, as well as specimens from elsewhere, I conclude that the plants seem to fall, according to both treatments, into Ophioglossum nudicaule L. f. The specimens are very slender and delicate, to over 12.5 (usually 8-10) cm tall, with the blade at most 17 x 12 mm, attached 8-20 mm from the base of the stipe, elliptic to broadly ovate or almost orbicular, sessile, acute to almost truncate at the base, acutish to more usually obtuse to rounded and slightly apiculate at apex, very thin, rather coarsely areolate by rather prominent veins, the areolae becoming smaller and more isodiametric toward the margins, some of them divided by thinner veins into 2 or 3 smaller areolae, or containing 1 or 2 free-ending veins, the marginal cells mostly irregularly elongate parallel with the entire margins, the main basal veins 6-8; in Fosberg & Evans 47400 0 (rarely 1 or 2) sterile fronds from the rhizome, these with the stipes about equalling the elliptic, oval, or oboval blades; peduncle to 10.5 cm, usually 6-8 cm, spike 8-16 mm long including the sterile, apical portion, 1.5 mm wide including the sporangia, the sterile portion of the axis between the sporangia 0.2 mm or less wide, sterile apical part, if uninjured, 1-2 mm long, subulate. An attempt to place this population in one of the varieties recognized by Clausen failed. The plants range in size from small, as in var. nudicaule (var. typicum of Clausen), to almost the maximum for var. grandifolium. Small plants could fit var. minus. The blade is the wrong shape for var. laxum or var. tenerum,