J . Linn. i9oc. (Bot.),59, 379, p . 343
With 2 plates and 1 text-figure
343
Printed i n Geut Britain
Febmary, 1966
The cytological characteristics of the fern subfamily
Lomariopsidoideae sensu Holttum
BY S. K. ROY AND I. MANTON, F.R.S., F.L.S.
Botany Department, Leeds University
(Accepted f o r publication February, 1965)
INTRODUCTION
The three leptosporangiate fern genera with which this paper is mainly concerned,
Lomariopsis, Teratophyllum and Lomagramma are tropical stem climbers with entire or
simply pinnate leaves and acrostichoid sori. This reduced morphology and specialized
habit restricts the number of characters available for claasificatory purposes and any
additional ones which can be detected are potentially important. For this reason if for
no other the addition of cytological information has been long hoped for but success has
hitherto only been achieved for one species of Lomariopsis from Africa (Manton, 1959)
which however gave a result so anomalous (n= 39) that further information from other
species of the genus was clearly necessary before an interpretation could be offered.
A major difficulty in studying these plants is that many of them become fertile in
nature only when they have been able to climb to a considerable height above ground
but they are only able to do this under very humid tropical conditionswhich, in cultivation,
can scarcely be imitated outside an enclosed frame. This means in effect that some species,
Table 1. List of chromosome wunts on members of the subfamily Lmriopsidoideae
before the present conzmunication
country
chr. No.
Author
Bolbitis lonchophwa (Kunze) C. Chr.
N. Zealand
n =82
B . semicwduta (Bak.)Ching
B . divemifolk (Bl.) Schott
B . singaporensis Holttum
B . subcrenata (Hk. & Grev.) Ching
B. aurioulata (Lam.)
&ton
B . acrostichides (Afzel. ex Sw.) Ching
Egenolfia appendiculata (Willd.)
J. Smith
E .appendioulata (Willd.) J. Smith
E. appendiculata (Willd.) J. Smith
E . wplenifolk (Bory) F6e
E . sp.
S. India
Malaya
Malaya
Ceylon
Ghana
Ghana
n=41
2n-82
2n =82
2n =82
n = c . 82
n=41
Brownlie (personal commun. in
Fabbri, 1963)
Abraham, Ninan & Mathew, 1962
Manton, 1954
Manton, 1954
Manton & Sledge, 1954
Manton, 1959
Manton, 1959
S. India
Ceylon
Malaya
S. India
E . nodifira F8e
ElapbglosazMlt krajinae Biswas
E . hirtum (Sw.) C . Chr.
E . spathulaturn (Bory) Moore
Teratophyllum wilkesianum (Brack.)
Holttum
L m r i o p s i s guineensis (Underw.)
Alston
Siam
Ceylon
Ceylon
Ceylon
New
Caledonia
n=41
n=41
n=41
n=41
n=41"+41'
(triploid)
n=41
n=41
n=41
2n=c. 160
n = c . 40
Species
-
Ghana
n = c . 39
Abraham, Ninan & Mathew, 1962
Manton & Sledge, 1964
Manton, 1954
Abraham, Ninan & Mathew, 1962
Bhavanandan (personal commun.
in Fabbri, 1963)
Manton & Sledge, 1954
Manton & Sledge, 1954
Manton & Sledge, 1954
Manton & Sledge, 1954
G . Brownlie (Dersonal commun.
in Fabbri, 1963)
Manton, 1959
344
S. K. ROYAND I. MANTON,F.R.S., F.L.S.
notably those from Milaya, are never likely to be fertile in cultivation though they can
be kept alive vegetatively for many years. For these the only source of cytological information is root tips and the only satisfactory technical method the modification of
the Chambers' snail cellulase squash method as described by Roy & Manton (1965).
By means of this we have now been able to study successfullya number of wild gatherings
from Africa and the oriental tropics, all maintained in cultivation a t Kew for periods
ranging from 10 years to a few months for recent arrivals.
The Lomariopsidoideae aensu Holttum (1949) contain 6 widespread genera : Elaphoglossurn, Egemlfia, Bolbitis, Terabphyllum, L i m a r i p . s and Lomagramma, together with
a 7th somewhat peculiar genus Thysanosoria, native only to New Guinea. Chromosome
counts, already published for species of the Grst 3 genera, are assembled in Table 1. They
are uniformly based on a monoploid of 41, a prime number which is found in many other
groups of fern genera (e.g. Dryopteroids, Davallioids). No living material of Thysanosoria
has yet been obtained but information on the other 3 genera is the subject of this paper.
MATEEUAL
A list of specimens investigated is given in Table 2 together with the chromosome
numbers found. The identscations were in the fist instance supplied by the collectors
but the cultivated specimens have in each case been versed in Kew herbarium either
by Prof. R. E. Holttum or Dr. F. M. Jarrett. The Table includes one new species of Bolbitis
for convenience of comparison with former work.
Table 2 . List of species and chromosome numbers rewrded bere for thejirst time
Species
country
Collector
Chr. No.
Lomariopsis cochinchinemis FQ
New Guinea
Malaya
Malaya
L. pineensis (Underw.)&ton
L. palustris (Hook.)Mett.
L. ros& Holtt.
L. hederacea &ton
Lomccgramma sinC. Chr. foma papwcna C. Chr.
L m m m a m e l a d p i s v. Ald. v. Ros
Gh8m
Ghana
Ghana
New Guinea
New Guinea
R. E. Holttum
R. E. Holttum
R. E. Holttum
C. D. Adam
C. D. Adam
2n = 82
2n=82
2n= 164
2n=78
n=39*
2n=78
2n = 62
2n=32
2n= 82
2n=82
Bolbitis mumannii (Kuhn) Ching
l'ercstophyllum luakna (FBe) Holtt.
Ghana
C. D. Adama
C. D. Ad-
R. E. Holttum
R. E. Holttum
* Meiotic count published by Manton (1959), the root tip count is new.
COMMENTS ON THE OBSERVATIONS
Root tip counts of most of the specimens examined are illustrated in P1. 1 and 2 .
Terutophyllum ludens (Pl. 1, fig. 2) and both species of LOmaGgramm (Pl. 2, fig. 3) are
straight forward, agreeing exactly with Bolbitis (Pl. 1, fig. 1) in showing 2n=82, i.e.
they are diploids with n =41 as expected.
h r i o p s i s wchinchinensis is more difficult since the chromosome number i s higher.
P1. 2, fig. 1 and Text-fig. 1 nevertheless show that this plant is a tetraploid on 41 with
2n = 164.
The African species of Lomariopsis in contrast are all aberrant. The accuracy of the
previous record for meiosis in L. guineensis has been fully confrmed by a root tip count
(many times repeated) in the same species (Pl. 2, fig. 3 ) and by an identical record for
one further species (L. palustris, P1. 2 , fig. 2 ) . The unusual number, n=39, is therefore
definitely a part of the genus as represented in Africa.
The other two numbers present (2n= 62 in L. rossii and 2n =32 in L. hederacea) are
even more unusual and though different numerically these 2 species share another
The fern subfamily Lomariopsidoideue sensu Holttum
345
peculiarity which is also unusual namely the mixture of large and small chromosomes
present together in one nucleus. Occasional members of the Hymenophyllaceae, notably
H . tunbridgense (Manton, 1950), can be compared in this respect with the strikingly
dissimilar chromosome sizes encountered within each of the karotypes illustrated in
P1. 2 , figs. 4,3 .
Text-fig. 1. Lomariopsis cochinchinensis, root tip squaah (Explanatory diagram t o P1. 2 , fig. 1.)
x 1,500.
DISCUSSION
I n interpreting the group as a whole it is important to notice that among species so
far investigated, cytological aberrations are limited t o African species of Lomariopsis
and are not shown by any of the other genera or by the one non-African species of
Lomariopsis ( L . cochinchinensis),obtained from Malaya. There is no reason therefore t o
question the primitire monoploid as having been n = 41 throughout the group.
I n such a context, none of the numbers 39,62 or 32 encountered in the African species
of Lomariopsis can be interpreted as primitive. Interpretation is nevertheless greatly
hampered by lack of fuller information. The genus Lomariopsis is pantropic in distribution
and contains some 50 accredited species only 5 of which have as yet been sampled
cytologically. Cytological information from the New World. from other parts of the Old
World including islands in the Indian Ocean (Holttum, 1939a),as well as further information from Africa itself, for which less than half of the known taxonomic species (cf.
Holttum, 1939b) have yet been sampled, will be needed before an explanation can be
offered for the apparently anomalous condition of the African flora as represented here.
This topic must therefore for the time being be left aside.
Chromosome numbers apart, a fact of exceptional phyletic interest is the range of
different chromosome sizes encountered within the genomes of 2 of the African species
346
S. K. ROYAND I. MANTON,
F.R.S., F.L.S.
(L. r o ~ iand
i L.hederacm). Karyotypes of this sort are so unusual in ferns that there
are virtually no other known examples among hundreds of species except in the totally
unrehted Hymenophyhcem. This character is thus most unlikely to be primitive and
some explanation in terms of chromosome fusion, fragmentation, hybridization between
karyotypes with Merent chromosome sizes, or some other type of change affecting only
a part of each genome seems necessary to explain it.
Further information which might permit a decision to be made between these various
alternatives might be expected to come either from study of meiosis or from comparative
cyto-morphology of a population as opposed to a single individual. In the special case
of L. hederacea (Pl. 2 , fig. 4) the morphology of the smallest chromosome a t first sight
recalls that of centric fragments and they might therefore prove to be 'supernumariesI ,
i.e. numerically fluctuating or genetically inert extra pieces perhaps duplicating parts
of the larger chromosomes but not essential for morphogenesis of the organism. Positive
confirmation of this suggestion would not however solve the problem of interpreting the
karyotype of such a species since removal of the small chromosomes would reduce still
further the si@cant chromosome number, which in the given taxonomic setting, would
make it more rather than less anomalous. Unless therefore it could be shown that
taxonomic error has been made with regard to these species, the possibility that
chromosome fusions may have contributed to their present condition cannot be
eliminated.
This raises a matter of much more than local interest. The high chromosome numbers
prevalent among leptosporangiate ferns is one of their most conspicuous attributes, yet
the opportunities and mechanisms for increasing chromosomes without detriment to
the individual are on the whole greater than for reducing them. The latter cannot however
be wholely excluded and the potential importance of L.hederacea lies in the fact that
it might represent a species which, by devious routes, has reverted to a numerical condition
which in other groups would be relatively primitive but which in this group can only
have been acquired secondarily by reduction from a higher number. This possibility is
the most important single finding of the present investigation and one which will fully
justify any further attention which could be given to the genus Lomariop~sin any tropical
flora in which these or additional species could be studied.
SUlldMdaY
Chromosome counts have been made and the karyotypes illustrated for species of
Bolbitis,Teratophyllum,Lomagramma and Lcnwriopis, all included within the subfamily
Lomariopsidoideae for which 6 out of the 7 genera contained in the subfamily have now
been sampled. With the sole exception of African species of Lmriopsis all are uniformly
based on a monoploid of n =41. The 4 African species investigated are all anomalous,
having chromosome numbers conspicuously less than 41. The suggestion is made that
a t least some of these numbers imply chromosomereduction perhaps through fusion from
a previously more normal condition. The nature of desirable further evidence is indicated.
ACKNOWLEDGEMENTS
Grateful thanks are due to the donors of material listed in Table 2 and also to the
Directors and many others on the staff of the Royal Botanic Gardens, Kew, notably
Mr. H. Bruty, O.M. the foreman of the ferneries, and Dr. F. M. Jarrett of the Herbarium.
Finally special mention should be made of Professor R. E. Holttum who contributed
not only most of the specimens and their names but who has also read the manuscript
and assisted in countless ways over many years. To all of these the authors tender
their best thanks.
Joun1. Linn. Su1·. /Jut. J",,f_ ;i !l . .Y (). :{ /!1
Pi nt (' l
2n=82
2
2n=82
3
:-;_ K. HOY "' ' ' I \ 1.\\:TO\:. F . !-:.-;_, F !..'.
Journ. Linn. A'oc. Bot. Vol. 59 Xo. 379
S. K . ROY
Y V I ) 1.
l I A N T O S , F.K.S.. F.1, S.
Plate 2
The fern subfamily L m r i o p i d o i d e a e sensu Holttum
347
REFERENCES
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F., 1963. Prinio supplemento alle Tavole cromosomiche delle Pteridophyta di Albert0 Chiarugi.
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R. E., 1939b. X e w Species of L O T W T ~ OK~e Sw ~Bull.,
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EXPLAXATIOX O F PLATES
PLATE
1
Fig. 1. Bolbitis naumannii.
Fig. 2. Teratophyllum Idem.
Fig. 3. Lomngramma slnuata.
All x 1000.
PLATE
2
Fig. 1. Lomariopsis cochinchinemis.
Fig. 2. L. palustris.
Fig. 3. L . guineemk.
Fig. 4. L . hedcracea.
Fig. Z. L. rossii.
A11 x 1000.