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characters. It has been pointed out (e. g. by Strömfeit 1. c. and by Kjellm. 

 Handbok 1. c.) as specifically characteristic to Alaria esculenta, that the 

 sporophylls were placed in a furrow in the stipe. I have also, but rarely, 

 in my material found the sporophylls growing in such a furrow, but 1 

 have on the other hand met with plants having the sporophylls placed on 

 an edgelike prominence of the stipe. Consequently the furrow in the stipe 

 cannot be used as a specifically distinctive character. The foursided shape 

 of the midrib has also been used as a specific character, but, as will be 

 shown in the following, this character is not always to be relied upon. 



I have met with young specimens of Alaria esculenta, which had a 

 remarkable midrib only in the lower part of the lamina. The midrib 

 was broadest and approximately plain below, and tapering and more and 

 more curved upwards. Older and larger specimens, which also were yet 

 in their first year, had a distinct midrib through the whole lamina. The 



Eig. 22. Alaria esculenta (L.) Grev. 

 a, b transverse section of the upper part of the midrib, c, d of the lower part 



of the midrib of the same specimen, in natural size (compare the text), 

 e, f transverse section of the lower part of the midrib somewhat enlarged and 

 schematized (compare the text). 



two broadest sides of the midrib were plain and parallel in the lower 

 part, but above the midrib was convex. The stipe of these specimens 

 was 4 cm. long, the lamina 60 — 80 cm. long and 2 — 2,5 cm. broad, and 

 the development of sporophylls had begun. The section of the lower 

 part of the midrib was limited by two longer, parallel and straight lines 

 and two shorter, curved lines, the section of the upper part was elliptieal 

 (cfr. fig. 22). 



At Reykjavik I examined a great number of fully developed, living- 

 specimens, having a length of 3— 4 m., and they had always in the upper 

 part of the costa an elliptical section (fig. 22, a, b), in the lower part a 

 section with the two longer sides straight and parallel and the two shorter 

 sides curved (fig. 22, c, d), and this is the normal shape of the costa in 



