No. 3] REMARKS ON NORTHERN LITHOTHAMNIA. 53 



I mentioned above, in treating of Lithoth. Ungeri, that 

 in a couple of specimens of this species from Iceland I have 

 found both four-parted sporangia and two-parted ones, also the 

 latter apparentl} 7 fully developed, but in small numbers. In L. 

 Iceve, which normally bears sporangia four-parted, I have often 

 seen two-parted ones, sometimes even only two-parted ones, parti- 

 cularly in the northern part of the arctic zone. But having found 

 in other specimens, partly from the same places, both two-parted 

 and four-parted ones, sometimes even in one and the same con- 

 ceptacle, 1 think it fair to presume that the two-parted ones have 

 not been fully, or normally, developed. L. foecundum, which is 

 of rather rare occurrence, shows nearly the same condition of 

 things. L. Lenormandi exceptionally bears two-parted sporangia 

 according to Thuret (in herb.). In L. flavescens, which usually 

 also bears four-parted sporangia, 1 have seen two-parted ones only 

 in a singh case, viz. in a specimen from Spitzbergen. In Litho- 

 phyllum incrustans usually occur four-parted sporangia, but now 

 and then also two-parted ones. Cp. Fosl. Noiw. Lithoth. p. 97 

 as to such organs in specimens from France. Besides, in Phy- 

 matolithon loculosum I have seen, in young specimens from the 

 Kurile Islands approaching Ph. compactum in habit, both four- 

 parted and apparently mature two-parted sporangia even in one 

 and the same conceptacle. On the other hand, the sporangia of 

 Ph. compactum are normally bisporic, but sometimes four-parted 

 ones are met with, particularly in fjords in the southern part of 

 its area of distribution, or exceptionally irregularly three- or four- 

 parted ones. Cp. L. testaceum Fosl. Norw. Lithoth. p. 107, and 

 Rosenv. 1. c. p. 776, 781. Also in Lithophyllum (Dermatol) 

 macrocarpum the sporangia are usually bisporic. But now and 

 then are found four-parted ones in the southern area of its distri- 

 bution. Still in Melobesia Lejolisii I have seen two-parted spor- 

 angia apparently fully developed and four-parted ones in the same 

 conceptacle, the latter, which are the usual ones in this species, 

 being in great majority. Evidently it is only in the areas boreal- 

 arctic and antarctic that the Lithothamnia are liable to developing 



