. The Canadian field-naturalist. 70 The Canadian Field-Naturalist Vol. 94 Heteranthera dubia, are more common than pre- viously thought. Ceratophyllum echinatum is very distinct from Ceratophyllum demersum when in fruit. Its fruits are wing-margined with several lateral spines (Figure 1). Vegetative parts are usually finer than those of Cera- tophyllum demersum and leaves tend to be dissected three times. It is, however, difficult to distinguish sterile plants of C. echinatum from finer forms of C. demersum. There is a slight difference in the setaceous hairs, which in C. echinatum start direc
. The Canadian field-naturalist. 70 The Canadian Field-Naturalist Vol. 94 Heteranthera dubia, are more common than pre- viously thought. Ceratophyllum echinatum is very distinct from Ceratophyllum demersum when in fruit. Its fruits are wing-margined with several lateral spines (Figure 1). Vegetative parts are usually finer than those of Cera- tophyllum demersum and leaves tend to be dissected three times. It is, however, difficult to distinguish sterile plants of C. echinatum from finer forms of C. demersum. There is a slight difference in the setaceous hairs, which in C. echinatum start directly from the leaf margin but in C. demersum start from small cor- niculate teeth (Fassett 1953). Both species have dis- tinctive flavonoid patterns. The problematic speci- mens can thus be reliably identified by a standard. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ottawa Field-Naturalists' Club. Ottawa, Ottawa Field-Naturalists' Club
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