Contribution. I. H5 



often attenuated towards the summit. A solitary specimen 

 in my collections is almost reniform and somewhat oblique, 

 6 cm. long and 10 cm. broad in the broadest part. The 

 largest specimen I have seen is 24 cm. long and 6 cm. broad. 

 In general the plant is smaller, 8 -12 cm. long and 3 — 6 cm. 

 broad. It is densely folded, the folds extend mostly to the 

 middle line of the frond, and the margin is much crisped. The 

 colour varies between light and rather dark green. The plant 

 has a somewhat loose consistency, is slimy and feebly shining. 

 A cross section a little above the callus corresponds fully 

 with fig. 9 b by W i 1 1 r o c k. In the monostromatic part 

 of the frond the cells are ovale or vertically rectangular 

 with rounded corners, seldom semicircular, 18 — 24 \k high 

 and 6 — 15 (J. broad. The chlorophyllous body occupies so- 

 metimes almost the whole cell, sometimes only a part of it, 

 but, as far as I have seen, it never is disciform and hori- 

 zontally rectangular. Cp. W i 1 1 r. 1. c. p. 48, t. 3, fig. 9 d. 

 Perhaps this difference at least partly derives from Wittro ck's 

 only having dried specimens for examination. 



The form Farlowii is distinguished from the typical one 

 by its thinner frond, being mostly cuneate-lanceolate, elon- 

 gated- obovate or lanceolate, attenuated towards the base 

 ai)d more or less obtuse at the summit, — contrary to the 

 shape of f. typica. It is less folded and the colour frequ- 

 ently paler than by the latter. The monostromatic part of 

 the frond is 18 — 20 \k thick by Finmarkian specimens, and 

 the structure similar to that of the typical form. Farlow 

 certainly quotes M. pulchrum having a thickness of only 6 

 [x, but specimens from Nahant, Mass., communicated to me 

 by Collins under the name of M. pulchrum are in the 

 middle, monostromatic, part of the frond about 30 jj. thick. 

 Perhaps Farlow's measurment refers to tbe uppermost part 

 of the frond, or the specimens have been younger. 



The species in question is litoral (f. typica and f. Far- 



