138 



upwards at least, sometimes separable by pressure. They are 

 square or most frequently rectangular, 8 — 10 p. long and 6 — 8 /* 

 thick including the walls, which, however, are rather thin. 



The conceptacles of sporangia are very densely crowded nearly 

 over the whole frond, not forming any defined zone, and are here 

 and there emptied before the adjacent are fully developed. They 

 are immersed, in the earliest stage of development that I have 

 seen at first perceptible from the surface of the frond as minute, 

 indistinct and slightly depressed-circular points. By and by these 

 points by decortication become more distinct and rather sharply 

 defined, at length forming shallow deepenings, the bottom of which 

 forms a part of the roof about 100 — 120 /a in diameter, and then 

 intersected with about 15 — 20 rather coarse and six-angular mu- 

 ciferous canals. At the same time is shown a very indistinct 

 border around this part of the roof, not .raised above the surface 

 of the frond, but visible by its colour being a little lighter. To- 

 wards maturity the part of the surface between the densely crowded 

 borders gets by and by thinly decorticated, and at length also the 

 latter are sharply defined, looking a little elevated, frequently six- 

 angular or rounded-angular, surrounding the above named part of 

 the roof, about 60 — 80 \j- broad and rather flattened, and the whole 

 roof including the border about 200 — 250 fJ- in diameter. PI. 22, 

 fig. 8. At maturity the whole roof, including the border which 

 also forms a part of the roof, falls away, leaving angular, often 

 regularly six-angular, holes of the named diameter with thin walls, 

 like a mesh-work. Also a smaller or greater part of the walls 

 disappears, and the remaining scars by and by become effaced by 

 new formed tissue The certainly not numerous sporangia that I 

 have examined quite likely were mature, bisporic and 130 — 160, 

 seldom up to 200 fi long and 40—55, now and then up to 60 

 y. broad. 



Relation to oilier species. It seems to be closely related in 

 habit to L. durum Kjellm. 1 ), the surface, however, being more 

 uneven. Also the conceptacles of sporangia apparently much re- 

 semble the similar organs in that species. I have not seen any 

 i) Beringh. Algfl. p. 22, t. 1. fig. 3—5. 



