223 



(comp. fi^. 138). The same author finally slates thai the fihunenls of the h y|)OlhalHum 

 are "t'ormees de cellules arrondies, Ires serrees les unes conlre les autres, de sorte 

 qu'il est impossible de suivre le trajet de chaque 

 file". As will be seen in my fig. 138, the filaments 

 of the hypothallium are very distinct in well 

 developed crusts. The cells of the perithallium 

 are roundish, sometimes almost globular, usually 

 however longer than broad, 7 — 10,5 // long, 4 — 8 /j 

 broad. They are often fused together two or three 

 in a horizontal direction. The crust is divided in 

 zones by horizontal lines stained intensely by 

 hsematoxyline. 



The branches have a similar structure to 

 the perithallium in the crust. The cells are 

 usually oblong or rectangular with rounded angles. 

 They are sometimes situated more closely toge- 

 ther in the outer layer than in the inner, that 

 is to say, Ihe walls are thinner (fig. 139 A). The 

 cells are 5 — 7 m broad, 7 — 11m long. Transverse 

 fusions between the cells are frequent, often 

 connecting several cells; in tangential sections 

 they are often especially numerous and appear 

 as irregular, curved, partly ramified formations 

 (fig. 139 C). In transverse sections of the central tis- 

 sue they 

 may pre- 

 sent a si- 

 milar ap- 

 pearance 

 (fig. 139 



Fig. 138. 



IJtholhuniniun (/laciulc var. Granii. A, vertical 

 section of crustaceous frond with sporangial 

 conceptacles. 65:1. B. part of the same sec- 

 tion, showing the hypothallium and a peri- 

 pheral part of a conceptacle. 350: 1. 



Fig. 139. 



Lithothainiiion glaciale var. Granii. A, longitudinal 

 section of upper end of a hranch. B, transverse sec- 

 tion of branch, from the centre. C. tangential section 

 of branch. 400; 1. 



B). These 



cell-fusions contain, at least usually, only one 

 nucleus (comp. p. 211, fig. 128). Starch grains 

 appear very irregularly, without relation to 

 the layers. The cells may contain a greater 

 or smaller number of them, and they may 

 consequently be placed closely together; but 

 composed grains (comp. Mme Lemoine, 1. c. 

 p. 94) do not seem to occur. 



Conceptacles are frequently found, but 

 only sporangial conceptacles were observed. 

 They are usually placed on the branches, 



