. The Canadian field-naturalist. Natural history. 2002 Aiken and Buck: Aquatic Leaves and Regeneration 85. Figure 4. A specimen cut longitudinally through the node where a new shoot (ns) was developing. Upper por- tion with the base of the new leafy stems (ns) was arising at the node (n) of an otherwise hollow stem. Lower portion is the other side of the stem above. The previous season's stem (ps) is hollow, and the node (n) is a solid partition across the hollow stem. The lack of roots on the sprouting shoots when they were collected was probably a reflection of an environment where moisture
. The Canadian field-naturalist. Natural history. 2002 Aiken and Buck: Aquatic Leaves and Regeneration 85. Figure 4. A specimen cut longitudinally through the node where a new shoot (ns) was developing. Upper por- tion with the base of the new leafy stems (ns) was arising at the node (n) of an otherwise hollow stem. Lower portion is the other side of the stem above. The previous season's stem (ps) is hollow, and the node (n) is a solid partition across the hollow stem. The lack of roots on the sprouting shoots when they were collected was probably a reflection of an environment where moisture was not limiting growth. Early in development, the need of the straw of A. fiilva to develop photosynthetic tissue was apparently greater than the need to develop roots. Although a very different system, the seeds of wild rice (Zizania palustris) germinating where water is not limiting, also develop photosynthetic tissue before producing roots. (Aiken, 1986). The contrast in the growth response between the samples observed on Banks Island and those observed in Ottawa probably reflects the difference in tempera- tures at the two locations. The difference in light quality or day-length may have been responsible for the new growth in Ottawa quickly turning green, while the new growth in plants on Banks Island remained reddish. In the Ontario transplant, A. fiilva behaved as a periodic species (that is, one in which development is halted at a particular stage even when abundant opportunity for further growth remains (Sorenson 1941). It might have been tempt- ing to interpret the plants as a genetically dwarfed arctic race of the species towards the northern limit. 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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