12 
THE STRUCTURE OF MOSSES. 
Tlie leaves of mosses are always sessile and broad based. 
In shape they vary from rounded to very narrow and pointed, 
but are never lobed or divided. They have no branching 
veins, but frequently have a midrib, sometimes two, and 
are often finely toothed on the edges. 
The stems in one section are mostly upright and slightly 
branched. In another mostly decumbent and very much 
branched in a pinnate fashion. 
These two sections are very distinct, and form well 
'marked divisions of the order. 
The upright mosses bear their fruit at the points of the 
stems and are called acrocarpous. The much branched 
creeping mosses bear their fruit along the sides of the stems 
and are called pleurocarpous. 
Now we come to the fructification. At all times of the 
year there are some mosses bearing their fruits, but the 
spring and the autumn are the most prolific. Mosses as a 
rule love moisture, and they get most of it at these seasons. 
Some time before the appearance of the fruit, the 
antlieridia and arcliegonia are formed hidden in the axils 
of the leaves, or among the tuft of leaves at the top of the 
stem. These organs are very minute, and have only been 
known to exist as sexual organs within the last fifty years. 
They occur sometimes both together on the same plant, and 
sometimes each on a separate plant. 
The antlieridia are mostly long oval bodies filled with 
ciliated antherozoids which have a power of locomotion in 
water. The arcliegonia are rounded at the base and tubular 
above, and the antherozoids pass down the tube to reach and 
fertilise the oosphere. 
After fertilisation the oosphere develops into a straight 
stalk which grows vigorously upwards, tears asunder the tube 
or neck of the archegonium, and carries away the top of it in 
the form of a cap called the calyptra. Within this cap the 
top of the stalk begins to swell, and gradually grows into a 
hollow capsule of very interesting construction. In the centre 
is a little pillar called the columella , round which the spores 
cluster thickly. Surrounding the mouth are one or two 
circlets of fine teeth called the peristome, sometimes brightly 
coloured, and often strongly liygrometric, opening and closing 
with changes of moisture in the air. Above the peristome is 
the lid, or moveable cover of the capsule, which has often a 
long beak, and which drops off when the capsule is ripe to let 
the spores fall out. Above the lid is the calyptra, a kind of 
hood or penthouse protecting the young capsule, which at 
last outgrows it and pushes it off, leaving the lid exposed. 
