of the cell, after the throwing off of the hair. As these cells are very different 
from the heterocysts of the Cyanophyceæ, I think it better to give them another 
denomination; they must be named hair-cells or trichocytes (comp. p. 213). They 
are somewhat larger than the other cells. Sometimes also, other intercalary cells 
than the branch-producing ones may develop into a trichocyte, and it may also 
happen that a trichocyte produces a cortical cell. These cells appear to be of 
normal occurrence, though varying in number". 
In the monostromatic part of the crust the cells are 7—10(11) » broad, and 
usually 1—11/2 times as long. The dimensions are somewhat variable (comp. figs. 
156 and 158). In specimens from the inner Danish waters (Sf and Sm) the breadth 
of the cells was only 7—9z, 
in specimens from Lf and 
Kn it was up to 114; this 
is possibly caused by the 
difference in salinity of the 
water. These cells often 
contain numerous starch 
grains, but the trichocytes 
contain no starch. The 
cortical cells are always 
longer in transversal than 
in radial direction. Trans- 
versal fusions between the 
cells may occur, some- 
times in great number 
(fig. 156 B). In a verti- 
cal radial section the 
cells are seen to be of 
Fig. 157. 
Melobesia Lejolisii. Vertical sections of conceptacles. A, from Stensnæs, Km, 
sporangial conceptacles. B and C from Kragenæs, Sm; B, with carpogonia, about the same height as 
C, with undivided sporangia, in the middle a columella. 350:1. 
breadth. 
The marginal part of the frond remains monostromatic, the small cortical cells 
not taken into account. Only in the immediate vicinity of the conceptacles the 
frond consists of 2—3(4) layers of cells. As the conceptacles are densely placed in 
the greater inner part of the crust, the frond is monostromatic only in the marginal 
part. The statement of Mme Lemorne (Structure, p. 180, fig. 103) that the crust of 
! The trichocytes appear to be variable in their occurrence also in M. farinosa. In specimens 
from LE Joris, Alg. mar. de Cherbourg no. 194, which, as shown by FOSsLIE, is a typical M. farinosa, 
I found the characteristical trichocytes quite in accordance with the descriptions of Rosanorr and 
Sorms. On the other hand, in the Melobesia communicated in Crouan’s Exsice. no. 244, which indeed 
is referred to M. Lejolisii by Fosuie, I did not find any heterocysts at all. This alga agrees, however, 
otherwise with M. farinosa, by the dimensions of the cells (L1—14 broad, about 11/°—2 times as long) 
and by the round, not transversely elongated cortical cells. I suppose therefore that it is a form of 
M. farinosa, in which no trichocytes have been developed. 
