105 



bears more or less scattered knobs, which in general are thinner 

 than in f. clensa, up to about 1.5 mm. thick, but frequently less, 

 and up to about 2 mm. high, subcylindrical, with rounded or oc- 

 casionally obtuse apices. The colour appears to be a darker pink 

 than in the named form, judging from dried specimens. This form 

 requires closer examination of larger materials than I have at my 

 disposal. 



The form rosea distinguishes itself by its thicker knobs, about 

 2 — 3 mm,, which are not so densely crowded as in f. clensa, 

 cylindrical, cylindric-conical or occasionally upwards thickened, in 

 the Norvegian specimens not exceeding 5 mm. in height, but in 

 British until 8 mm. according to B at ters 1. c. In most of the 

 specimens that I have seen the knobs are simple, in others occa- 

 sionally on the point of dividing, or carrying a small wart-like 

 process, but Batters remarks that they also are bind or trifid 

 above. The crust is as thick or thicker than in f. clensa. Pl. 17, 

 flg. 12 — 13 represents Norwegian specimens, fig. 15 — 16 British, 

 and fig. 14 an American specimen from Rockport, Mass. (Collins' 

 collection F.). 



The above quoted forms accord with each other as to the 

 structure. The knobs show in a longitudinal section more or less 

 regular cup-shaped layers of tissue, with the inner cells frequently 

 longer in proportion to the thickness than those in a section of 

 the upper thickening-layers of the crust, 8—12 p long and 5 — 8 

 p thick, with rather thin walls. 



The conceptacles of sporangia in f. clensa are scattered or 

 somewhat crowded in or between the knobs, seen from the sur- 

 face 300 — 350 p in diameter, very little prominent and as a rule 

 rather flattened. The roof is intersected with 30—40 muciferous 

 canals. The sporangia are two-parted, much varying in shape 

 and size, convex-concave and frequently with the rounded or now 

 and then rather attenuating ends somewhat bent together, occa- 

 sionally nearly half-moon shaped, and large in proportion to the 

 height of the conceptacles, in general about 180—220 p long and 

 60 — 100 p broad, or more. I have, however, seen but few con- 

 ceptacles and sporangia of this form. 



