. Il campo Canadese-naturalista. La figura 1. La distribuzione oiC. passerinum in Ontario sulla base di campioni di erbario (cerchi cortesia G. W. Argus, Divisione di botanica e il Museo Nazionale del Canada, e triangoli generosamente fornita da J. L. Riley). estratto mediante il numero di piante o i gruppi trovati al momento la caratteristica è stato osservato o misurato. Il lavoro sul campo è stata effettuata il 6 Giugno al 19 luglio, 1979. Per ottenere informazioni sulla crescita negli anni precedenti, rizomi sono stati esaminati su 26 fioritura o vegetativa di grandi impianti distribuiti tra 22 gruppi. Surfi- cial detriti e sabbia sono stati delicatamente accantonando per reve

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. The Canadian field-naturalist. Figure 1. Distribution oiC. passerinum in Ontario based on herbarium specimens (circles courtesy G. W. Argus, Botany Division, National Museum of Canada, and triangles generously provided by J. L. Riley). mined by the number of plants or groups found at the time the characteristic was observed or measured. Field work was carried out 6 June to 19 July, 1979. To obtain information on growth in previous years, rhizomes were examined on 26 flowering or large vegetative plants distributed among 22 groups. Surfi- cial debris and sand were gently brushed aside to reveal the shallowly-buried rhizomes. Distances between stalk scars (Figure 2), depth, and direction of growth were noted. Mean annual growth increments were calculated for 5-year intervals up to 1975-1979. Floral development was observed for flowering shoots in 34 groups. The relative contribution of sex- ual and asexual reproduction to group expansion and maintenance was first determined for 20 flowering groups. Seedlings were identified by a gradually taper- ing rhizome less than 1 cm long. In groups where seedlings were not obvious, the rhizome of the young- est plant was examined by carefully loosening the soil around it. Based on experience gained from these 20 groups, the presence/absence of seedlings in the remaining 22 flowering groups was determined with- out disturbing the soil, through observations of size, morphology and distance to other plants. Several procedures were carried out in an effort to determine the insect pollinators of C. passerinum. The exit holes at the base of the column in 10 flowers were plugged with cotton in order to trap pollinators in the lip. The lips were examined several times a day for a number of days after the exits were plugged. Secondly, insects were collected from nearby plants to be examined for the presence of C. passerinum pollen, but these were lost in transit. Thirdly, six hours (dur- ing both daylight and dusk) of four days during

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