282 
Lang . — The Prothallus 
others had a more complicated outline. One of them is 
represented from the side in Fig. 4, which shows that the 
increase of the longitudinal curvature has brought the two ends 
into actual contact, while a single secondary fold is visible. 
Each lateral margin of the similar prothallus represented in 
Fig. 1 showed two such secondary folds. 
The resemblance in form and habit which these prothalli of 
* L . clavatuni presented to those of L. annotinum 1 rendered it 
probable that the structure would be similar in the two cases. 
As will be seen, this similarity was found to exist even in 
points of detail. In Fig. 5 part of a vertical section across 
the lateral margin of the prothallus shown in Fig. 3 is re- 
presented ; the corresponding sections of the ends presented 
a similar arrangement of tissues. As will be seen from the 
figure, a number of layers of tissue can be distinguished which 
agree, in relative thickness and in the characters of the cells 
composing them, with the layers described by Bruchmann in 
L. annotinum 2 . This distinction of layers appears to stand 
in relation to the localized distribution of an endophytic 
Fungus, the characters of which will be described toward the 
end of this paper. The slightly flattened cells of the outer- 
most layer (a, Figs. 5, 6), which bounds the prothallus on the 
under surface, are quite free from the Fungus, with the 
exception of some of those prolonged as rhizoids. The outer 
layer of the free walls of these cells gives the reaction of 
cuticle ; this is especially marked at the base of a rhizoid. 
The latter structures are as a rule simple extensions of 
superficial cells, but in some cases the main part of the 
rhizoid is separated by a transverse wall from the basal 
portion. ! Above the lower limiting layer comes a band of 
cells three or four deep (b, Figs. 5, 6), which are extended 
parallel to the surface of the prothallus. These cells, as well 
as the succeeding single layer (c, Figs. 5, 6 ), which consists of 
more or less regular palisade-shaped elements with their long 
1 Fankhauser, Bot. Zeit., T873, p. i; Bruchmann, Bot. Centralblatt, xxi, 1885, 
P- 23. 
2 Loc. cit., 1 88s. 
