136 



turning downwards, at length attaining a thickness of about 1 cm. 

 It is more os less uneven, which, however, often depends on the 

 substratum, as it frequently covers shells of Balanidæ and other 

 animals fastened to the rock, or grows over animals fastened to 

 younger crusts of the plant itself. But it also is provided with 

 subhemispherical or irregular processes, or new local and irregular 

 crusts are form ed upon the older. Pl. 19, fig. 5 — 9. Is is extre- 

 mely traversed by worms especially in the lower layers, so that 

 it here often rather resembles a mesh-work. The surface appears- 

 perfectly smooth to the naked eye, as if it were polished, but 

 magnified shows here and there rather indistinct concentric and 

 radiating striæ, sterile crusts feebfy shining but fertile not. The 

 peripherical portion is rather thin, but not concentric zonated, nor 

 is the brim whitish. 



The conceptacles of sporangia are irregularly scattered nearly 

 over the whole frond, or here and there crowded, but on the whole 

 scarce in the specimens gathered. They are at first visible from 

 the surface of the frond as minute lighter points, imperceptible to 

 the naked eye, about 100 — 130 p. in diameter, the roof of the con- 

 ceptacles. The latter by and by gets thinly decorticated at first 

 in the centre, later the whole roof, intersected with about 10 — 15 

 muciferous canals, and at length forming depressed-circular points 

 of the named size. At maturity the whole roof gets dissolved,. 

 frequently at first the central portion, the surrounding parts con- 

 tinue their growth and the conceptacles become overgrown. They 

 are in a median section spherical or nearly spherical, about 100 

 — 140 /-/- in diameter. The sporangia are four-parted, 90 — 120 /£ 

 long and 25 — 50 ;j. broad. 



Overgrown conceptacles frequently appear to be numerous. 

 In most of those examined I found all or nearly all the sporangia 

 not escaped, many of which have been apparently mature when 

 they together with the conceptacles grew down into the frond. 



The cells of the upper thickening-layer are seen on a radial 

 section to be arranged in straight, well-marked rows, rectangular 

 or sometimes nearly square, about 10 fi long and 7 — 8 i>. thick,. 

 with not or scarcely not rounded corners. 



