PARK AND CCME^TCRY 
268 
Layers are put down when the young acer polymokrhum. 
shoots are of sufficient length in early summer, and late winter, in a greenhouse,, the stock for both this 
are better let remain undisturbed for two seasons. and inarching purposes being the polymorphum, the 
Grafting is usually performed on potted plants, in one of the illustration. 
Garden Plants — Their Geography — CXII.— Filicales. 
Adiantum pedatum. 
The Gleichenia, Polypod- 
ium and Ophioglossum Al- 
liance. 
Exclusive of such ancient 
and intermediate tribes as 
Equiseteae and Lycopodese 
ferns have about i8 Tribes, 
75 Genera, and 3,000 or 
more species. Additions 
have been made especially 
to tree ferns since this 
enumeration was made, but 
it may be expected that the 
1 eduction of so-called species will about balance them. 
Perns are tropical, sub-tropical, warm and cold tem- 
perate (rarely arctic) evergreen or deciduous leafy 
herbs, sometimes climbing by stems or rhizomes, or by 
their upright caudices which often thicken by aerial 
roots, they become trees of 20 to 50 or more feet high. 
They are especially abundant in the sub-tropical climates 
at considerable elevations on the tropical mountains. 
Often they are epiphytal, sometimes on each other, and 
occasionally sub-aquatic. They are really a part of a 
separate division of plants which Jussieu called Acoty- 
ledones. The roots are fibrous, rhizomatous and some- 
umes tuber bearing. The budding leaves are rolled up 
like the spring of a watch, and when expanded are 
simple or compound, the infertile leaves sometimes 
differ from the fertile, and many differ greatly in the 
vanous stages of their growth. The mature plants 
have neither flowers nor floral organs. When these oc- 
ciir at all they are borne in an infinitely small state by 
the “prothallium,” a remarkable vegetative process 
which I will try to give an idea of presently. In place 
of seed, too, the leaves often bear millions of minute 
and volatile spores, as light and easily wind borne as 
the pollen grains of grasses or pines. This character 
has facilitated the spread of many species to all suitable 
parts of the world. These spores are naked, or borne 
in little cases on the under sides or edges of the fronds, 
or on the modified rolled up leaves of the so-called flow- 
ering ferns. Unlike pollen, it is unnecessary for them 
DICKSONIA PILOSIUSCULA. 
