206 THE MOSSES OF ESSEX :
pyriformis, a common moss of the peaty soil of heaths in the
county, usually found in tufts covered with the broken leaves.
No species of moss is restricted in its British distribution to
Essex, although until recently Zygodon forsteri had been found
only in this county, at first on a felled tree in Walthamstow at
the beginning of the last century; later, on beeches in at least
two localities in Epping Forest. It has now been found in two
other English counties. It is curious that wherever this moss
occurs it is always found in a very scattered fashion, both in this
country and on the continent. One would scarcely look for
such an alpine species as Grimmia commutata in Essex, but Mr.
H. N. Dixon found it growing on the roof of a house at Wickham
Bishops; perhaps other alpine species may be discovered
occasionally in a similar fashion if search is made for them. It
was suggested that possibly the spores had been carried by the
wind across the North Sea from the mountains of Norway,
where the moss is common.
Among species of which there is at present no record for the
county, but which should be found here, may be mentioned
Polytrichum urnigerum, P. gracile, Seligeria pauci folia, Ditrichum
schreberi, Leptodontium flexifolium, Encalypta streptocarpa, Bryum
pendulum, B. donianum, Mnium stellare, Hypnum polygamum, and
H. lycopodioides.
Not only is there much to be done in Essex as far as mere
species recording goes, but anyone taking up the study of the
mosses will find them of much interest in themselves. We have
to deal with a series of plants in which the gametophyte genera-
tion has reached the fullest development forming the leafy plant,
while in all other plants the leafy plant belongs to the sporophyte
generation with the sole exception of the nearly allied Hepaticae.
The Musci have followed a line of development of their own, and
it has come to an end with the more elaborate of their forms.
The manner of obtaining water is full of interest and varies
greatly in the different species, affording matter for much study;
the form and papillosity of the leaves, the arrangements of
lamellae on the leaf surface, the presence of hair points, etc., are
all matters apparently closely connected with the obtaining of an
adequate supply of water. The part they play in the economy
of Nature, the relation they bear to other forms of life, particularly
as formers of soil, and lastly, a subject about which we probably