223 
(comp. fig. 138). The same author finally states that the filaments of the hypothallium 
are “formées de cellules arrondies, très serrées les unes contre 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 u 
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 
hæmatoxyline. 
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, the walls are thinner (fig. 139 A). The 
cells are 5—7 4 broad, 7—11 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 
9 B). These 
Fig. 138. 
Lithothamnion glaciale 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. 
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, l. c. 
p. 94) do not seem to occur. 
Lithothamnion glaciale var. Granii. A, longitudinal Conceptacles are frequently found, but 
section of upper end of a branch. B, transverse sec- only sporangial conceptacles were observed. 
tion of branch, from the centre. C, tangential section 
of branch. 400:1. They are usually placed on the branches, 
