76
THE ESSEX NATURALIST.
minate upon. The examples exhibited this afternoon were
taken from a moss-cushion 5" square. There were 28 germinat-
ing birch seeds, in various stages of development, upon it. The
cotyledons are epigeal. Counting from the left (Plate VI. fig. 1.)
No. 1 has hypocotyl 8 mm., cotyledon 2.5 mm., stalk of
cotyledon 1 mm.
No. 5 has hypocotyl 12 mm., cotyledon 4.0 mm., stalk of
cotyledon 1 mm.
No. 6 has hypocotyl 11 mm., cotyledon absent (fallen).
No. 1 cotyledon glabrous, 1st foliage leaf trilobed, shaggy,
hairy.
No. 5 cotyledon glabrous, 1st foliage leaf narrowly trilobed,
shaggy, hairy.
No. 6 cotyledon fallen, 1st foliage leaf broadly trilobed,
shaggy. hairy.
No. 11 cotyledon fallen, 3rd foliage leaf broadly 5 lobed,
shaggy, hairy.
No. 13 cotyledon fallen, 5th foliage leaf broadly 7 lobed,
shaggy, hairy.
The younger of the roots exhibit signs of mycorrhiza, both
epitropic and endotropic, but the detail respecting them is left
for description at a later date. It would be interesting to dis-
cover whether the seed of the birch, like that of Calluna, is
unable to germinate without the presence of mycorrhiza.
The stem of the birch elongates rapidly for the first ten
years, lengthening as much as 2 to 2.5 feet the first year. Large
numbers of young birches are now covering the land, especially
on the eastern side, that, until recently, was enclosed as Paul's
Nursery at High Beach.
The birch grows to a height of 65 to 80 feet, and lives for
approximately 50 years.
The measurement of the circumference, at 3 feet above the
ground, of a large number of forest birches has been taken
during the last two years. Those with a circumference of less
than 15" have been neglected; they however form a large
proportion, as shown in the photographs of birch groves now
exhibited (Plate VII. figs. 1 and 2.)
Some of the largest on the Forest plateau are:—
(1) at High Beach, south of the churchyard, circumference 95"
(Plate VI. fig. 2.)