. The Canadian field-naturalist. 270 The Canadian Field-Naturalist Vol. 97 Results Distribution Fifty-two groups (899 plants) were found at the Pic River, 22 to the south and 33 to the north. Groups varied in size from one to 137 plants and, typically, were composed of both clones and separate individu- als. More detailed information on distribution is recorded in Keddy (1979. An Ecological Study of Cypripedium passerinum and Listera borealis. Report to Parks Canada, Ontario Region, Cornwall, Ontario. 126 pp.). Although other sandy shorelines in Pukaskwa National Park were explored during the
. The Canadian field-naturalist. 270 The Canadian Field-Naturalist Vol. 97 Results Distribution Fifty-two groups (899 plants) were found at the Pic River, 22 to the south and 33 to the north. Groups varied in size from one to 137 plants and, typically, were composed of both clones and separate individu- als. More detailed information on distribution is recorded in Keddy (1979. An Ecological Study of Cypripedium passerinum and Listera borealis. Report to Parks Canada, Ontario Region, Cornwall, Ontario. 126 pp.). Although other sandy shorelines in Pukaskwa National Park were explored during the period of peak flowering, no new locations were found. Morphology C. passerinum is a perennial species with a horizon- tal rhizome which grows a new segment each year and produces a leafy aerial shoot at its tip. In the specimen examined (Figure 2), two roots were produced by each annual segment. Buds on the rhizome develop into lateral branches. After many years and much branch- ing, a rhizome network is formed and many appar- ently separate plants may be interconnected beneath the sand surface forming a large clone. Rhizomes generally grow parallel to the soil sur- face. The older portion of the rhizome tends to occur slightly deeper than the most recent portion, likely due to sand and litter accumulating above it over the years. At those sites where sand was obviously accumulating (sand rained down during field work), the rhizomes were growing at a 45° to 60° angle from the horizontal plane, rather than parallel to it. Rhi- zomes were buried deepest in moss-covered areas, where they occurred at the interface between a dark organic layer and 5 to 9 cm of partially decayed moss. Rhizomes were shallowly buried ( cm) where the surface was sand or litter. Plants can be approximately aged by counting the stalk scars (one scar per year); however, after several years, the oldest part of the rhizome rots and disinte- grates. Thus, ages determined by rhizome examina- tion may u
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