Thomas.— Notes 071 Cephaleuros. 789 
If sections be cut perpendicularly to the leaf surface, it will clearly 
be seen that the Alga grows between the cuticle and the inner layers of the 
epidermal cell-walls. This is shown by the continuity of this membrane 
with that which occurs externally to the Alga. The cells of the epidermis 
and even of subjacent layers are affected by the presence of the Alga. 
The cell-contents become massed into dense aggregates, reddish brown 
in colour, and the walls become sclerotic (Fig. 12). In surface view, 
when the Algal patches are removed, the outlines of the discs may be 
traced owing to the darkened surface thus exposed, the presence of the 
Alga having brought about this degeneration. 
In transverse section the large cells of the Alga show a clear lumina, 
and from the lower surface of the cells grow the ‘ rhizoids ’. In surface 
view these are seen as irregular cells, much branched and curved (Fig. 11) ; 
they occur in abundance between the cells of the disc and those of the 
epidermis of the leaf. Owing to their curvature, in a transverse section 
of the Alga the * rhizoids ’ are cut in various directions, so that circular 
ends in cross-sections and curved longitudinal pieces occur together 
(Fig. 13 ). 
These { rhizoids ’ are not penetrating organs, and nothing of the 
nature of a haustorium has been seen. They may become closely ad- 
pressed to the walls of the epidermal cells, but in no case has penetration 
been observed. 
Nuclei stain prominently in haematoxylin, both in the thallus cells and 
in the rhizoids. 
In the thalli, zoosporangia are frequently to be observed. In surface 
view they appear as terminal cells of a ‘filament’ which has enlarged 
and whose cell-contents are much denser. Haematoxylin picks out the 
nuclei ; cases have been observed with one, a few, or numerous nuclei 
(Figs. 10 and 11). In section it may be seen that the zoosporangium 
becomes very much swollen, the swollen part projecting downwards. The 
wall of the zoosporangium becomes thickened and the nuclei lie irregularly 
in the granulated protoplasm (Fig. 14). 
In addition to these fertile cells, an end cell of a ‘ filament’ may give 
rise to a barren or fertile hair ; these hairs grow vertically upwards, 
perforate a way through the ‘ cuticle and thus reach the outer air. The 
barren hairs are simple structures, long, and consisting of several cells, 
as a rule arising from a thallus cell with dense cell-contents (Fig. 15). 
The sterile hairs are about the same diameter all along their length, 
but certain others become very much swollen at the ends. The terminal 
cells of the latter have dense cell-contents and a prominent nucleus 
(Fig. 16). 
Many stages have not been observed, but a few examples show a cell 
cut off from the apex of the hair, comparable with and closely resembling 
3 H 
