225 



Lithothamnion calcareum Ellis et Sol. var. noroegicum Areschoug, Observ. pliycolog. III. 1875, p. 4. 

 Lilholhamnion coralloides Crouan f. noruegica (Aresch.) Foslie, Norw. Forms 1895, p. 62, tab. 16 fig. 1 — 11. 



According to Foslie, this species is almost always freely developed on the 

 bottom (Remarks p. 66). The specimens found in the Danish waters were all loose. 

 Foslie has referred them all to f. pnsilla which, in his opinion, is "perhaps the 

 typical form of the species". He observes however (1. c. p. 64 and 67) that they 

 "partly approach stunted forms of L. nodulosum f. gracilescens" . They give off 

 branches in all directions and become up to 3 cm (more rarely 3,5 cm) in diameter. 



The anatomical structure is not very different from that of L. glaciale. According 

 to Mme Lemoine, the cells are in the greater part of the frond rectangular, while 



near the periphery they are ovoid. This may be so, but it frequently happens that 

 rectangular cells in the inner parts of the frond alternate with ovoid ones (fig. 143 C). 

 The change may take place at the distinctive lines between the zones or indepen- 

 dently of them. The zones are limited by somewhat irregular lines staining deeply 

 by haematoxyline, and the staining power of the single layers may sometimes be 

 a little different, but the limit between such zones is not always marked as a blue 

 line (fig. 143 C). The irregular course of the distinctive lines is probably in accordance 

 with the irregularity of the increase. Transverse fusions between the cells frequently 

 occur, though not so frequently as in L. Granii, and not uniting so many cells as 

 in that species. The cells are 8—14// long, 6 — 9« broad; the rectangular ones are 

 11 — 14/y. long, 6 — 7// broad. The central tissue shows a different aspect in trans- 

 verse section, according to whether the section has fallen in a zone with rect- 

 angular or with roundish cells. The appearance of the starch is variable. It may 

 appear in great quantities in the more deeply stained and in the less stained 

 zones as well, all the cells being filled with starch grains except the outermost ones. 

 In other cases it is entirely or almost entirely wanting. 



Conceptacles were found in specimens from most of the localities named below; 



B 



Fig. 141. 



Lithothamnion glaciate var. Granii. Vertical section of sporangial 

 coiiceptacle with ripe sporangium. 350:1. 



Fig. 142. 



Lithothamnion glaciale var. Granii. A, 

 sporangium; the process of division not 

 yet completed. B, ripe spore. 390:1. 



I). K. {). Vidc-nsk. Selsli. Skr., 7, lUukUe, natiii viileiisk. of? niiitliem. Aid. VII. 2. 



29 



