FERNS
Seth Bigelow & Peter Kukiehe cloud forest of Monteverde is graced by an
awe-inspiring diversity of ferns, which range
in size from minute filmy ferns to towering
tree ferns and in habitat from dry roadside to mist-
shrouded forest canopy. More than 350 species (Table
3,7) are known from Monteverde and the upper Penas
Blancas valley. The fern flora is decidedly high alti-
tude in character, with over half the species having
lower altitude limits above 500 ni and a third hav-
ing lower limits of over 1000 m. More than 60% of
the species have ranges extending from southern
Mexico down into South America, with 11 species
also occurring in the Old-World tropics. Twenty-
seven Monteverde fern species are near the northern
extent of their ranges in Costa Rica, and seven reach
their southernmost extent there. Monteverde itself is
not notable as a site of fern endemism, although 29
of its species are endemic to Costa Rica and Nicara-
gua or Panama.
Ferns constitute a primitive and ancient division
of plants, the Polypodiophyta, whose basic features
evolved several hundred million years before those
of the flowering plants. Their life cycle has two
phases, one sexual and one nonsexual, which live
independently of each other. The nonsexual, spore-
bearing (sporophyte) phase is familiar to most people,
but few are aware of the sexual (gametophyte) phase;
these forms are tiny and look unfernlike. Features for
distinguishing fern sporophytes from other plants are
(1) fronds that uncoil as they grow, producing a
"fiddlehead" appearance, and (2) spores produced on
the underside of fronds.
Though of varied shapes, most ferns have a basic
structure of fronds (leaves) attached to a rhizome
(stem). Rhizomes may be completely underground and
are either massive and woody or trailing and vinelike.
Fronds have two main parts, the stipe (leaf stalk or
petiole) and the blade (the leafy portion of the frond).
The blade may be simple or divided into leaflets
(pinae), which may be further subdivided into pin-
nules. The central axis of a divided leaf is the rachis.
The reproductive features of ferns are used in iden-
tifying species. Spores develop in aggregations called
sori (singular = sorus), and each group of ferns has a
characteristic sorus pattern. Presence or absence of a
protective flap of tissue that covers the sorus (indusium)
is another useful character. Species that do not bear
spores on all fronds are referred to as dimorphic; fertile
fronds often look markedly different than sterile ones.
The most common terrestrial ferns of disturbed
areas around the MCFP include Adiantum continuum
(Dwarf Maidenhair Fern), which coats the banks along
the road just above the Pension FlorMar; Blechnum
occidentals, small and leathery ferns common along
the road 1.5 km before the MCFP; Odontosoria gymno-
grammoides, a vinelike fern of abandoned fields,
steep roadbanks, and landslides; Pityrogramma tar-
tares (Silver-back Fern), an open-area fern with a
white, flourlike coating on the underside of the fronds;
Pteridium aquilinum (Bracken Fern), a cosmopolitan
species complex that thrives in pastures and along
roads throughout the Monteverde area; Sticherus
retroflexus, a vinelike fern commonly seen dangling
down exposed roadbanks in the upper Monteverde
area and showing a distinctive architecture in which
two pairs of zigzagging secondary rachises emerge
from the primary rachis at regular intervals; and
Thelypteris rudls, one of the most common ferns in
Monteverde found lining roadsides and trails through
the MCFP.
Common terrestrial ferns of the forest interior in-
clude Bolbitis oligarchica, found in shady moist spots
in the lower elevation of the MCFP; Diplazium urtici-
folium, which is recognized by the combination of
chevron-shaped sori and terrestrial growth habit and
is common along most trails of the MCFP, in clusters
over 1m tall; and Pteris altissima, a large fern found
along many trails, especially at lower elevations.
Tree ferns, massive palmlike ferns that may exceed
15 m in height, are mostly in the Dicksoniaceae or
Cyatheaceae families (Fig. 3.17). Epiphytic ferns in-
clude the genera Asplenium (Spleenworts), Elapho-
glossum (Paddle Ferns), Grammitis (Dwarf Poly-
podies), Hymenophyllum and Trichomanes (Filmy
Ferns), Oleandra bradei, Niphidium nidulare, Neuro-
dium lanceolatum, Compyloneurum sphenodes, and
Vittaria (Shoestring Ferns).Acknowledgments We are indebted to M. Grayum
for discussion, editing, and species identification. We
thank N. Nadkarni, J. Longino, K. Clark, N. Barbour,
the Monteverde community, and the herbarium of the
University of California, Santa Barbara. This was a
student project of the University of California Educa-
tion Abroad Program in Tropical Biology and was
published as a field guide pamphlet in 1991 by the
Tropical Science Center and The Marie Selby Botani-
cal Gardens.89 Plants and VegetationT