180 



maturity the central portion of the roof often gets a little flattened- 

 or even depressed. This portion at first becomes dissolved, later 

 the greater part of the roof, but so far as I have seen, always 

 leaving a smaller or larger border. These borders contribute to 

 the unevenness of the frond, and the rest of the emptied concep- 

 tacles get effaced by local formations of tissue The tetrasporic 

 sporangia are about 60 — 80 p. long and 20 — 35 \i broad. I have, 

 however, examined but some few of the latter. 



In f sublævis the conceptacles frequently are a little larger 

 than in f. typica, the roof 300 — 400 fi in diameter, and more flat- 

 tened, sometimes in this respect rather approaching those of L. 

 Stromfeltii and not densely crowded. I have seen only one or 

 two specimens of this form from Helgoland and from Berwick on 

 the British coast, and a small one from the Christiania Fjord only 

 provided with cystocarpic conceptacles probably belongs to the 

 same form. The surface appears to be smoother and the colour 

 darker than frequently in f. typica. However, it is possible that 

 this form perhaps constitutes a separate species, although the limits 

 seem to be very difflcult to draw. 



prehended parti}' as such partly as animals, and often referred to various 

 genera. Cp. Giimbel, Die sogen. Nullip. p. 17. The name Nullipora 

 was constituted by Lamarck 1. c. as genus-name, and by him it comprehends 

 calcareous algæ principally of the later genus Litliothamnion Phil.' The 

 oldest genus-name applied only to species of the latter is Apora, recorded by 

 Gunnerus, which could be adopted for Litliothamnion with the same 

 pretension as Tenar ea for LithophyUum. Thus Gunnerus remarks with 

 regard to his Apora polymorpha in Act. Nidros. 4 (1768), p. 21, t. 8: 

 „Man tinder ei, paa disse, Stierner eller Porer (hverken Milleporarum eller 

 Celleporarum) ; hvorfor de Orme, som beboe denne Corall, maa soges imellem 

 dens Grene eller de smaa Rum, som flere sammengroede, af denne Art, 

 foraarsage, eller og i de Hull, som Ormene selv paa adskillige Maader bore 

 igjennem dens Grene. Af denne Aarsag synes mig, at den udgjør et nyt 

 Genus, som jeg kalder Apora". Cp. above under L. fruticulosum and 

 L. coralloicles. However, I find no reason to replace neither the denomi- 

 nation Litliothamnion nor LithophyUum for any other previous to those 

 of Philip pi, which have been maintained for nearly 60 years. 



On the other hand I agree with Mr. Hariot that the species-name 

 undidosa ought, perhaps, to be adopted for L. cristatum, if the latter in 

 the sense tåken by Solms-Laubach and Hauck 1. c. does not include 

 more than one species. 



