156 



authentic specimen from Hauck's herbarium for examination. Be- 

 sides, in a collection of Lithothamnia from Helgoland, that Dr. 

 Kuckuck had the kindness to send me, I found several fertile 

 specimens of the plant. I have seen but a solitary Norwegian 

 specimen which is not quite typical and ought, perhaps, to be 

 considered a denominated form of the species. Two small Bri- 

 tish specimens, gathered at Cumbrae by Mr. B at ters, fully ac- 

 cord with Helgolandian ones, the one being sterile but the other 

 provided with some few conceptacles of sporangia. 



There is some difference between younger but sporangia- 

 bearing and older individuals. The former rather approach L. 

 Stromfeltii and L. Lenormandi in habit, and sometimes closely 

 resemble the flgure of the last named species by Hauck l.c. t. 

 3, fig. 4, partly with nearly smooth surface partly with scaly 

 thickenings or minute excresences. Some younger specimens from 

 Helgoland that I got under the name of L. Lenormandi belong 

 to the present species. Old specimens resemble the quoted flgure 

 (5) by Hauck 1. c. and are easily recognized and even in a ste- 

 rile stage rather characteristic. 



The conceptacles of sporangia are scattered over the whole 

 frond in great numbers, and often two or three quite confluent. 

 They are circular or nearly circular in circumference, very little pro- 

 minent and nearly always flattened, often disc-shaped or nearly 

 disc-shaped, frequently 350—400 p in diameter seen from the sur- 

 face. Towards maturity the central portion becomes more or 

 less depressed, by and by falling away, and at length the whole 

 roof gets dissolved, ieaving a rather shallow scar, sometimes, 

 however, with the exception of a small peripherical portion. The 

 scars get effaced partly by a new thickening layer of the frond 

 partly by new local formatipns, which contribute to the uneven- 

 ness of the surface. The roof is intersected with 80 — 100 muci- 

 ferous canals. The sporangia are four-parted, 100 — 140 p long 

 and 35—60 p broad. 



The conceptacles of cystocarps sometimes occur in the same 

 individual bearing those of sporangia sometimes and most fre- 

 quently in other individuals, and are scattered in great num- 



