Apical Growth in the Genus Trentepohlia. 241 
THE STRUCTURE OF THE CELL-WALL AND THE 
APICAL GROWTH IN THE GENUS TRENTEPOHLIA. 
By G. S. West, M.A., D.Sc., F.L.S., 
AND 
Olive E. Hood, M.Sc. 
[With Figs. 1—6.] 
HE remarkable structure of the cell-wall of Trentepohlia Montis- 
Tabulce var. ceylcinica, which was very briefly commented 
upon at the time that variety was described, 1 has since led to a 
detailed examination of the cell-wall of this and other members of 
the genus. 
The structure of the cell-wall and the growth of the apical cell 
in this species from Ceylon are first dealt with, after which briefer 
statements on the structure of the wall in other species are given 
for comparison. 
Trentepohlia Montis-Tabul/£ (Reinsch) De Toni var. Ceylanica, 
W. & G. S. West. 
This is a large Trentepohlia with a thicker cell-wall than occurs 
in any other known member of the genus. The cells are 52—57/x 
in length, 19— 34^ in breadth, and the cell-wall attains a thickness 
of 7*5 (or even 8) /x. It is distinctly lamellose, exhibiting a peculiar 
and characteristic oblique surface striation. De Toni 2 describes 
the walls of the type-form as “ thick and lamellose, with very 
delicate, decussating striations.” 
In surface view the wall has the appearance of a network of 
interlacing fibres, but in optical section it is seen to consist of 
somewhat oblique lamellae, all of which are slightly divergent upwards. 
This structure is rendered more evident if the filaments are cleared 
and caused to swell, which can be done in a most satisfactory way 
either by the use of concentrated sulphuric acid or an ammoniacal 
solution of cupric hydrate. Under this treatment the lamellae 
gradually swell up and separate, giving the plume-like appearance 
represented in Fig. 1. A similar swelling can also be brought about 
by treatment with concentrated potash solution. 
The transverse walls are also lamellose, the lamellae being con¬ 
tinuous with those of the lateral walls. The form of the transverse 
1 W. & G. S. West in Trans. Linn. Soc., bot. ser. 2, 1902, p. 131. 
* De Toni, Syll. Alg., 1889, p. 240. 
