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A MONTHLY JOURNAL
With SPECIAL REFERENCE TO THE FACTORS OF EVOLUTION
I. THE DEVELOPMENT OF CERTAIN KELPS
A. Renfrewiał For the preparation of a former article (Griggs, '06) on Renfrewia the writer had no very young plants, but during the summer of 1907 he was enabled to collect a full series at the Minnesota Seaside Station, Port Renfrew, B. C. This material is of interest for the study of the development of this, the most primitive of the kelps in comparison with the more complex forms.
The smallest specimen found, which measures a trifle less than 4 mm. (Fig. 1), is not certainly determinable. But one 13 mm. long (Fig. 2) had already developed a peculiar swelling of the basal region which characterizes the young plants. The primitive disc of most kelps and of Renfrewia up to this age is rather flat and sharply separable from the stipe, which ascends cleanly without tapering from the top of the disc. In Renfrewia, however, the basal region of the stipe (the region which in other kelps develops hapteric outgrowths) increases in size. As the plant grows this swollen region becomes more prominent till in plants 8 cm. long (Fig. 11) the
Since publishing the original account of Renfrewia parvula in 1906 I have found that it is apparently conspecific with Setchell's ('01) Laminaria ephemera earlier described from the California coast. Accordingly Setchell's name replaces mine and the plant becomes Renfreuia ephemera (Setchell). Cf. Setchell, '08 b.