. The Canadian field-naturalist. 1mm. 10cm Figure I. Stages in the life-cycle of the Ostrich Fern. A. Gametophyte with archegonia (a) in the central anterior, and antheridia (an) in the basal portions. B. First leaf of juvenile sporophyte (jl) which is still partially dependent on the gametophyte (g) for nutrition. C. Mature sporophyte with large sterile fronds (s) and smaller fertile ones (f). Both types are eventually shed, only the leaf bases (1 b) remaining, protecting stem and apex. Stolons (st), which have cataphylls (c) at intervals along their length, arise from the main rhizome. Roots
. The Canadian field-naturalist. 1mm. 10cm Figure I. Stages in the life-cycle of the Ostrich Fern. A. Gametophyte with archegonia (a) in the central anterior, and antheridia (an) in the basal portions. B. First leaf of juvenile sporophyte (jl) which is still partially dependent on the gametophyte (g) for nutrition. C. Mature sporophyte with large sterile fronds (s) and smaller fertile ones (f). Both types are eventually shed, only the leaf bases (1 b) remaining, protecting stem and apex. Stolons (st), which have cataphylls (c) at intervals along their length, arise from the main rhizome. Roots (r) develop extensively from the rhizome but only intermittently along the stolons. hairs was common to most specimens of M. struthiopteris, as did Tryon (1939). Another form of M. struthiopteris is obtusilobata, which has obtusely shaped pinnules (Fernald 1935). Formfoliacea, in which the leaves are intermediate between sterile and fertile fronds, and the European equivalents hypophylloides and epiphylloides (Luerssen 1889) are not thought to constitute good forms, as such intermediate leaves are known to occur in M. struthiopteris following surgical removal of the leaves (Goebel 1888) or adverse environmental conditions (Atkinson 1911). Forms recorded for European, but not North American, populations of the Ostrich Fern xncludtfurcata Baenitz, in which the frond apex has bifurcated, daedala Sauter, in which the apex has repeatedly bifurcated, and serrata Baenitz, the leaves of which have serrated edges (Hegi 1965). (g) Ecotypes. None reported. (h) Chromosome numbers. Numbers (n) of 39 (Fabbri and Menicanti 1970; Kurita 1976; Love 1976) ca. 40 (Britton 1953) and 40 (Friebel 1933; Okuno 1936; Sorsa 1958; Mitui 1965) have been reported. 3. Distribution and Abundance (a) Geographic range. The Ostrich Fern occurs as a native plant throughout the north temperate-sub boreal zone of the northern hemisphere, including North America, Siberia, southern China, Japan, Iran, Scandinavia,.
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