Bulletin of the EANHS 21 ( 23 ) 
18 
ARTICLES 
FERNS IN EAST AFRICA: A NOTE ON THEIR 
BIOLOGY, DISTRIBUTION AND CONSERVATION 
Introduction 
This note is put together to give general naturalists some 
idea of the diversity of ferns in East Africa. Because 
many people are understandably vague about what a 
fern is and how it lives, we have l»ad to make some basic 
explanations. Wehnve also tried 10 describe the general 
ecology' and distribution of the group to make field 
observations more meaningful Two accounts or ferns 
have recently become available, those of Johns ( 1 90 1 ) 
and Fadcn (1994). and many people will want some 
background information and generalisations about the 
Fern Flora of our region 
Ptcridophytes are situated between the mosses (non- 
vascular plants) and the higher plants in the evolutionary 
hierarchy of the plant world A distinctive anatomical 
feature of Pleridophyies which they share with higher 
plants — gymnosperms and angiosperms— is the 
presence of a water transpon (vascular) system in the 
plant body, but Ptcridophytes differ from the latter two 
divisions in lacking the seed habit: they reproduce by 
spores. 
The Ptcridophytes of East Africa are classified into four 
broad groups of spore-bearing plants that include whisk 
ferns (psilopsids), club mosses (lyeopsids), horsetails 
(sphenopsids) and ferns (filicopsids). These groups are 
not related to each other, being distantly descended 
from a hypothetical ancestor of the land plants in general. 
The rare psilopsids have no true roots or leaves, and 
the bristle-Iikc stems divide in two. repeatedly, bearing 
clusters of three spore- sacs. The club mosses have true 
roots and closely arranged scalc-likc leaves. Spore sacs 
are often crowded at the stem lips like cones. Ihe 
horsetails have tiny leaves in whorls or frills around the 
stem and spore sacs in groups, like anther?, crowded 
The EANHS wishes fo tha nk the follow- 
ing for (heir support in 1997: 
Sponsors of the Society: 
A. R. Gregory 
J.RE. Leakey 
Drs. T. Butynski & J. Kalina 
P. Colbert 
MJC. Minot 
T. Lehumberg 
A. Foresti 
S. Collins 
M. Rigby 
N. Heyer 
DrV.Somen 
into a definite cone a! the stem ups. The ferns are defined 
by having frond leaves that bear the spore sacs, usually 
on the lower side. 
The Ferns 
Life History 
All the Ptcridophytes have two phases of their life 
history: sexual and non-scxual. The sexual phase 
requires fertilisation of an egg by a swimming sperm 
and therefore needs free water at a critical time and this 
is a nsky business. The egg and the sperm arc called 
gametes and therefore the sexual plant is called a 
gametophyte and has one set (n) of chromosomes 
Because it needs a water film the gametophyte of the 
ferns is usually a liny thin green disk held close lu 
damp ground, and has a shod life during the rain) 
season, hul there ore interesting exceptions to this. The 
fiision of the gametes produces a cell with two sets of 
chromosomes (n*n = 2n) called a zygote This 
immediately grows into a fern plant Every fern plant is 
non-sexuttl. bearing spores which need no fertilisation, 
and so arc called sporophytes. The sports arc the result 
of dividing the chromosomes mto two similar sets (2ri - 
nit) The spores or.' dry and wind-borne over great 
distances so thut dispersal to suitable sites is rapid. 
But the> germinate and develop into the gametophyte 
with its chancy sexual reproduction and so few are 
successful in producing and fertilising an egg to grow 
into the next sporophyte germination (Raghavan, 1989). 
This process is called the ullernurion of generu/mns. 
This introduction to the biology' of ferns in East Africa 
discusses their ecological requirements and 
geographical distribution. Current changes in global 
and regional climates and habitats make their monitoring 
and conservation important. 
Ecology 
Ferns comprise a group of Ptcridophytes of about 
J. Ruparel 
N. Searle 
E. Bradley Martin 
C. Kathurima 
Corporate members: 
Elsa Conservation Trust 
Monsanto 
U.T.C. 
Major Donors: 
Royal Society for the Protection 
ofBirds 
