. The Canadian field-naturalist. 302 The Canadian Field-Naturalist Vol. 108 In North America, the Tolypella nidifica complex as defined by Wood (1965) extends in a broad belt across the northern and central United States enter- ing Canada only in the prairies of southern Saskatchewan/Alberta and possibly in extreme southern Ontario, although I am not aware of any Ontario records. It is recorded in eastern North America only as far north as New York State. Figure 5 illustrates its American distribution as presented by Wood (1967), however, it is not possible from Wood's sources to distinguish T
. The Canadian field-naturalist. 302 The Canadian Field-Naturalist Vol. 108 In North America, the Tolypella nidifica complex as defined by Wood (1965) extends in a broad belt across the northern and central United States enter- ing Canada only in the prairies of southern Saskatchewan/Alberta and possibly in extreme southern Ontario, although I am not aware of any Ontario records. It is recorded in eastern North America only as far north as New York State. Figure 5 illustrates its American distribution as presented by Wood (1967), however, it is not possible from Wood's sources to distinguish T. glomerata, T. longicoma, and T. comosa in this distribution. The Newfoundland discovery extends the range of T. glomerata in excess of 1500 km to the northeast without any known intermediate populations. The Newfoundland collection (51° 26' N) and the Saskatchewan record (Macoun 1879 in Wood 1965) are of approximately the same latitude and constitute the most northerly reports on this continent. Growing conditions are, however, quite different in these two locations, the Strait of Belle Isle site pro- viding generally harsher conditions including a shorter, cooler growing season, less unimpeded direct sunlight, and poorer nutrient conditions. The vascular floras of eastern North America and western Europe have a high proportion of related endemics, the "amphi-atlantic element". It appears that some migration of species has occurred in both. Figure 5. North American distribution of the Tolypella nid- ifica "complex" redrawn from Wood (1967). Arrow indicates Newfoundland location of T. glomerata. directions with the predominant movement from Europe westward (Hulten 1958; Dahl 1963). In addi- tion, many species have been introduced from Europe in historic times and are largely considered anthropophytes although direct evidence of alien invasion mechanisms and routes are only document- ed for a very few (Cooper 1981; Lindroth 1957). If many vascular plants ha
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