The Fern Alliance 
One period of the life of a fern is that known as the 
prothallium. In some ferns (Schizza bifida and Tricho- 
manes) the prothallium is very like an alga and pro- 
bably lives in water, but in most it is a little flat green 
and fleshy body which flourishes on continually damp 
soil.® 
So Von Wettstein gives a neat little figure showing 
the way in which land plants developed out of what 
was once a purely water-flora. 
This point has been elaborated in an important work 
by Professor Bower.® 
The alge and fungi are essentially water-plants, and 
the process of fertilisation is performed in water. The 
little free-swimming sperm cell or male cell swims to 
the egg cell and effects fertilisation under water. Then 
the egg cell begins to develop. In many alge and 
fungi it does not at once form a new alga, but grows, 
dividing many times, so as to form a number of cells, 
Some of these are the spores which will produce the new 
alga or fungus, but others may never become spores at 
all, Some cells will form a sort of shell or envelope to 
hold the spores, and others may become creeping fila- 
ments which attack the branches of the parent alga and 
absorb food material from them (e.g. Floridez). < 
This stage in the life-history from the egg to the 
spore may be called the spore-plant. This spore grows 
into what we call the alga, which produces the sperm 
and egg cells. In mosses the sperm cell also reaches 
the egg cell by swimming, for during the life of most 
mosses (especially in February to March in England), 
moss-tufts are often covered with rain water. The egg 
cell in mosses, when fertilised, grows and forms the 
elegant little stalk which ends above in a small capsule, 
from which the spores are distributed. The base of the 
stalk extracts food material from the mother moss, and 
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