. The Canadian field-naturalist. 182 The Canadian Field-Naturalist Vol. 90. Figure 2. Carex praegracilis, based on TRT 183213. a, achene; fg, female glume; 1, ligule; mg, male glume; p, perigynia; s, sheath. Drawing by Audra Geras. Mature plants of C praegracilis present an aspect markedly different from flowering specimens since the culms elongate considerably as maturity is reached. In southern Ontario the fruit matures and maximum height is attained in early July but frequently the highway verges have been mowed by this time, so specimens with mature perigynia may be difficult to obtain. So
. The Canadian field-naturalist. 182 The Canadian Field-Naturalist Vol. 90. Figure 2. Carex praegracilis, based on TRT 183213. a, achene; fg, female glume; 1, ligule; mg, male glume; p, perigynia; s, sheath. Drawing by Audra Geras. Mature plants of C praegracilis present an aspect markedly different from flowering specimens since the culms elongate considerably as maturity is reached. In southern Ontario the fruit matures and maximum height is attained in early July but frequently the highway verges have been mowed by this time, so specimens with mature perigynia may be difficult to obtain. Some patches occasionally remain uncut or a few culms are merely knocked down by the mowers. During the course of this study, however, plants from several localities were transplanted to allow for the collection of enough perigynia to ascertain the range of variation. In addition to their variation in size (Table 1), the perigynia were found to vary con- siderably in shape. The body ranged from sub- orbicular to ovate-lanceolate and tapered from abruptly to gradually, to a beak one-third to two- thirds as long as the body. The perigynia of C. foenea and C. sartwelli were observed to vary in parallel fashion. Highway verges are among the habitats most frequently neglected by botanists, yet these areas are most interesting with respect to introduced and adventive species. They provide essentially uninter- rupted corridors for long-distance dispersal and represent new habitats affording easy colonization with a minimum of competition. Dispersal may be rapidly accomplished, the seed being spread by mowers and highway traffic, and the sod and roots spread during grading of highway shoulders and by highway construction. Those species resistant to the extreme conditions of road verges, such as summer drought and high NaCl levels, would be favored. Carex praegracilis is said to be alkali-tolerant Table I—A comparison of C. praegracilis, C. foenea. and C. sartwelliiwhh respect to charac
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