240 



of the cell, after the throwing off of the hair. As these cells are very different 

 from the heterocysts of the Cijanophycece, 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) fj. broad, and 

 usually 1 — iVs 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 — 

 in specimens from Lf and 

 Kn it was up to 11 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 

 about the same height as 

 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 Lemoine (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 Jolis, Alg. mar. de Cherbourg no. 194, which, as shown by Foslie, is a typical M. farinosa, 

 I found the characteristical trichoc3'tes quite in accordance with the descriptions of Rosanoff and 

 SoLMS. On the other hand, in the Mclobesia communicated in Crouan's Exsicc. no. 244, which indeed 

 is referred to M. LcjoUsii by Fuslie, 1 did not find any heterocysts at all. This alga agrees, liowever, 

 otherwise with M. farinosa, hy tlie dimensions of the cells (11 — 14// broad, about IMj — 2 times as long) 

 and hy the round, not transversely elongated cortical cells. I suppose therefore tiiat it is a form of 

 M. farinosa, in which no trichocytes have been developed. 



C 



Fig. 157. 



Mclohesia Lejolisii. Vertical sections of conceptacles. A, from Stensnaes, Km, 

 sporaiiKial conceiilacles. B and C from Kragena-s, Sin; D. with oarpogonia, 

 C, witii iinclividcil sporangia, in tlip miihllc a columella. li^O.!- 



