THE PHILIPPINE
JOURNAL OF SCIENCE
VOL. XIII
C. BOTANY
NOVEMBER, 1918 NO. 6
MERRILLIA, A NEW RUTACEOUS GENUS OF THE TRIBE
CITREAE FROM THE MALAY PENINSULA
By WALTER T. SWINGLE
TWO PLATES
In the tropical regions of the Eastern hemisphere there occurs
a small but very well- marked group of citrous plants having
large fruits with a woody or leathery pericarp, and five or
more locules with numerous seeds embedded in a transparent
glutinous jelly. These so- called hard- shelled citrous fruits comprise
at present six genera and nine species, and range from the
Philippines west to Liberia in western Africa, and from India
and Indo- China to Java and other Malayan Islands. Aegle 1
with one species occurs in India and Indo- China, Balsamocitrus 2
with three species in tropical Africa, Aeglopsis with one species
in West Africa, Feronia with one species in India and Indo- China,
Feroniella 3 with two species in Indo- China and Java, and Chaetospermum
4 with one species in the Philippine Islands. These
six genera constitute a natural group inside the tribe Citreae.
This group I propose to recognize as a subtribe Balsamocit1' inae,
1 These genera and species I have described in popular form in L. H.
Bailey's Standard Cyclopedia of Horticulture. New York ( 1914- 1917).
' Swingle, Walter T., Le genre Balsamocitrus et un nouveau genre'
voisin, Aeglopsis, Bull. Soc. Bot. France 58 ( mem. 8d) ( 1911) 225- 245, t.
1- 5. RelJrinted in Chevalier, Aug., Novitates florae africanae, fasc. 4:
225- 245, t. 1- 5.
• Swingle, Walter T., Feroniella, genre nouveau de la tribu des Citreae,
fondee sur Ie F. oblata, espece nouvelle de l'Indo- Chine, Bull. Soc. Bot.
France 59 ( 1912) 774- 783, t. 18.
• Swingle, Walter T., Chaetospermum, a new genus of hard- shelled
citrous fruits, Journ. Washington Acad. Sci. 3 ( 1913) 99- 102.
158742 335
336 The Philippine Journal of Science
typified of course by Balsamocitrus. The genera of the Balsarrwcitrinae
are very different from each other and have many distinct
characters of taxonomic importance. In other words they
seem like the widely scattered survivors of a once larger group.
Subtribe BALSAMOCITRINAE Swingle
The genera of this subtribe fall into three divisions or supergenera:
( 1) Aegle, Balscvlnocitrus, and Aeglopsis, with very
hard- shelled fruits having many locules and trifoliolate or rarely
unifoliolate leaves; ( 2) Feronia and Feroniella, with very hardshelled
fruits with five locules coalescing into a single cavity,
and pinnate leaves; ( 3) Chaetospermum, with a leathery rinded
8- to lO- celled fruit and trifoliolate leaves.
Recently a new member of the Balsamocitrinae has come to
light in the Malay Peninsula. It is apparently most closely
related to Chaetospermum but differs widely from it as will be
seen from the account given below.
During the winter of 1917- 18 Professor C. F. Baker sent to
me at Washington a fine specimen of the fruit of Murraya
caloxylon Ridl., 5 from a tree growing in the botanic gardens
at Singapore. It was at once apparent that this fruit did not
belong to a plant of the genus Murraya ( Chalcas) but appertained
instead to the group mentioned above. As I did not have
a flowering specimen, I hesitated to publish on this plant because
it had so many aberrant characters that it seemed possible the
flower might show unexpected characters.
Upon reaching Manila in July, 1918, I was agreeably surprised
to find that Professor E. D. Merrill, acting director of
the Bureau of Science, had secured from Mr. 1. H. Burkill,
director of the Singapore Botanic Gardens, a beautiful flowering
specimen collected in March, 1918, and also fresh fruits from
the same tree. One of these fruits had been kept in the refrigerator
and was still fresh enough to be studied.
In the meantime Professor C. F. Baker, dean of the College
of Agriculture of the University of the Philippines, had brought
seeds from Singapore and planted them in the college nurseries
at Los Banos, Laguna Province, Luzon. These seedlings enabled
me to observe the germination characters.
Thanks to all this material, as well as my notes on the type
material of the species ( H. C. Robinson 5548) which, through the
courtesy of Mr. E. G. Baker, I was able to study in the British
• Ridley, H. N., New. or rare Malayan plants, Series IV, Journ. Straits
Branch Roy. As. Soc. 50 ( 1908) 111- 114.
XIII, C, 6 Swingle: Merillia, a new Rutaceous Genus 337
Museum, at South Kensington, in 1911, I now feel able to discuss
this remarkable species, in many ways unique among the plants
closely related to Citrus, In the first place all the known members
of the tribe Cit1" eae have either unifoliolate leaves or else
pinnate leaves with strictly opposite leaflets. The other genera
of the subfamily Citratae, such as Chalcas ( Murraya) , Clausena,
Glycosmis, and Micromelum, have pinnate leaves with alternately
arranged leaflets but never with a winged rachis. Up to now
a single leaf, even if hnmature, would serve to distinguish
any of these genera from the true Citreae. The Singapore
plant has pinnate leaves with alternate leaflets and a narrowly
but clearly winged rachis. All the pinnate- leaved members of
the subfamily Citmtae have a clearly marked petiole below the
first pair of leaflets. The flowering specimen of MU1' raya caloxylon,
collected in the Singapore Botanic Gardens in March,
1918, shows sessile or subsessile leaves, the lowest leaflets being
very small, nearly opposite, and attached near to or at the very
base of the rachis. The fruits are even more remarkable, being
like Chaetospe1' mum in having a leathery rind, but differing
widely in the irregularly lacunose pericarp and in having the
walls of the locules solid, The seeds at first glance seem to
be hairy like those of Chaetospermum and Aegle, but closer
examination of what appear to be hairs shows that they are
thin, elongated.. somewhat fimbriate paleae. The seeds also show
an ariloid ridge at one edge, unlike the seeds of the other members
of this subtribe.
Many other characters of less importance serve to mark off
this plant as perhaps the most remarkably aberrant of the
citrous fruits,
I take pleasure in naming this remarkable new genus in
honor of Professor E. D, Merrill, who has done so much valuable
work on the flora of the Philippines, the Malayan region,
and southern China.
MERRILLIA genus novum
( Rutaceae, CilJratae, Balsamocitrinae)
Genus Chaetospermo ( Roem.) Swingle ut videtur affinis
perspicue differt ovario 5- vel 6- loculare, pericarpio irregulariter
lacunoso, seminibus dense paleaceis, paleae elongatae, membranaceae,
leviter laciniatae, foliis sessilibus, pinnatis, rhachibus
anguste alatis, foliolis alternis.
Arbor inermis. Folia pinnata, sessilis vel subsessilis, rhachibus
anguste alatis; foliola alterna, inferioribus parvis" sursum
gradatim majores, terminalibus majoribus; petiolulo brevissimo.
338 The Philippine Joumal of Science 1918
Inflorescentia axillaris, 2- 1- floris. Floris ~, majusculi, 5- meri.
Calyx 5- partitus, parvus, lobis triangulari- ovatis. l'etala 5,
deorsum angustatis. Stamina 10, libera, inaequalia. Ovarium
5- rariter 6- loculare, stipitatum, in stylum elongatum attenuatum,
stigmate capitato; ovula in loculis 8 ad 10. Bacca subglobosa,
magna, pericarpio crassissime coriaceo, irregulariter radiatimlacunoso,
septis cartilagineis, loculis muco repletis, semina numerosa
( in quoque loculo ca. 8 ad 10), lenticularis, testa dense
paleaceis, paleae leviter fimbriatae, membranaceae, elongatae,
hilo carinato, subariloideo. Germinatione cotyledones subterraneae,
foliis primariis simplicibus, oppositis, late ovato- Ianceolatis.
The type species of this genus is Murraya caloxylon Ridl., a
tree native to the Malay Peninsula. It is known from southern
Siam and Upper Perak, and is in cultivation in the Singapore
Botanic Gardens.
Specimens examined: H.. C. Robinson 5548, Upper Perak,
Kenering, at 500 feet elevation ( British Museum, London);
I. H. Burkill, March, 1918, from a tree cultivated in the Singapore
Botanic Gardens, the specimen with flowers and fruits.
Only one species is known, the katinga of the Malay Peninsula
and Siam.
M ERR ILLIA CALOXYLON ( Ridley) Swingle comb. nov. Plates V and VI.
Murraya calaxylan Ridley in Journ. Straits Brancli Roy. As. Soc.
50 ( 1908) 113.
The original description is as follows:
Murraya calaxylan, n. sp.
A tree of considerable size the branches covered with a pale flaky bark.
Leaves 8 inches or more long with 13 leaflets, rachis flattened and winged
narrow, leaflets 3- 3~ inches long or less by a inch wide, alternate oblan.
ceolate obtusely acuminate with a triangular base, minutely petiolate
inequilateral thin bright deep green. Flowers pale yellowish green several
together in small panicles, in the upper axils of a branch, about
an inch long. Sepals connate ovate acute ~ o inch long. Petals and
stamens not seen. Ovary stalked, hairy, style rather stout hairy, stigma
capitulate. Fruit oblong rounded at both ends, 4 inches long and three
inches in diameter, the pericarp dotted and warty greenish eventually
becoming yellow, half an inch thick, lemon yellow inside, full of long
resin cells narrowed at the mouth and dilated below, cells 5, with rather
thick tough walls, pulp of transparent flattened sticky fibers olive green
in colour and tasteless. Seeds numerous about 5 in a section ovate
flattened half an inch long 11 inch thick, olive grey.
Southern Siam: Patani ( Penney); Upper Perak: Kenering at 500 feet
- elevation ( Robinson 5548).
This tree' known as the Katinga is famous in the Malay peninsula
lor its beautiful wood. Thjs handsome wood is of light yellow color,
XIII, C, 6 Swingle: Merillia, a new Rutaceous Genus 339
ornamented with dark brown streaks and strains, fairly hard in, texture
and taking a good polish. Mr. F. Penney obtained a considerable quantity
of the wood from Siamese territory North of Province Wellesley, from
which he had made furniture, boxes, etc., which was very highly valued
on account of its beauty. He obtained also leaves and fruit of the
tree. For the flowers I am indebted to Mr. H. C. Robinson, who met
with it in Upper Perak.
It differs from other species of the genus in the greater size of the
leaves, the conspicuously stalked ovary, and the remarkable fruit which
resembles a citron. The rind has a bitter terpentiney flavour, and the
comparatively scanty pulp is quite tasteless. The fruit is so entirely
different from that of any other species of the genus that the plant
might almost be separated generically.
In the introduction to the fourth series of New or Rare
Malayan Plants 6 the following paragraph occurs:
The well known furniture wood Katinga from the Siamese borders
has long been prized and I obtained leaves and a fruit some years ago
from Mr. F. G. Penney, who had a fine collection of furniture made from
its wood. A number of young plants were raised in the Botanic Gardens,
and I lately obtained specimens shewing parts of the flower from Mr.
H. C. Robinson. It proves to be a Murraya allied to the well known
Kamuning wood, so much valued for the handles and sheaths of Krises.
As Ridley did not have good flowering specimens or fresh
fruits the original description should be supplemented in · some
particulars and emended in others. The following notes were
made from the flowering specimen and fruit collected in March,
1918, from the tree cultivated in the Singapore Botanic Gardens.
The leaves of fruiting twigs are sessile, pinnate, with 6 to 8
alternate leaflets. The petiole is very short or wanting, the
rachis 10 to 15 cm long, narrowly winged, the wing increasing
in width gradually up to the point of attachment of the leaflets,
then suddenly diminishing. The leaflets are very unequal in size
and shape, the basal ones- sometimes a pair nearly oppositebeing
very small, 5 to 10 mm in diameter, and very broad, often
suborbicular. The lateral leaflets increase rapidly in size up
to the penultimate, and at the same time become narrower and
more pointed, becoming also somewhat inequilateraI. The penultilnate
leaflet is 70 to 80 by 20 to 30 mm, rhomboid- Ianceolate,
subacuminate at the apex but with the very tip bluntly rounded;
the base is cuneate. The terminal leaflet is like the penultimate
in shape but symmetrical, 80 to 100 by 30 to 35 mm. The
margins of the leaflets are wavy, sometimes slightly serrate.
The very young leaves, like the young twigs, are minutely
pubescent, but the older leaflets become nearly glabrous. The
• Ridley, H. N., op. cit., p. ~ 11.
340 The Philippine Journal of Science 1918
oil dots are small but very numerous. Inflorescences 1- or 2flowered,
axillary, pedicels slender with a few minute bracts.
The flower buds are very large, 35 to 45 by 10 to 12 mm, greenishwhite.
The petals are 35 to 40 by 5 to 10 mm, bluntly pointed
at the apex and narrowed gradually to the base. Stamens 10,
. unequal, filaments long, slender, free. Pistil 20 to 25 mm long,
slightly hairy, with a clavate ovary narrowing abruptly into
the cylindric style 12 to 15 mm long, which ends in a capitate
stigma. Ovary 5- or 6- celled, narrowing gradually toward the
base. Fresh fruits subglobose, when dry often slightly oval,
70 to 80 mm in diameter, nearly smooth, gray- green with a
leathery pericarp 10 to 12 mm thick with irregular branched
lacunae filled with a resinous gum; loculae 5 or 6, with cartilaginous
solid walls 3 to 4 mm thick, the locules filled with a
transparent jellylike gum surrounding the seeds. Seeds 8 to
10 in a locule, lenticular, 9 to 10 by 7 to 8 by 3.5 to 4 mm,
gray- green in color, abundantly provided with very thin, elongated,
hairlike, slightly fimbriate paleae 6 to 10 mm long, 0.25
to 2 mm wide. Near the hilum on the angle of the seed is a
light yellowish- gray ariloid ridge 5 to 7 mm long and 1 to 2
mm high; because of the numerous hairlike fimbriate paleae
the seeds almost completely fill the space, the interstices alone
being filled with transparent jellylike gum. In the fresh fruits
the paleae of the seeds being embedded in the transparent gum
are very inconspicuous, but become increasingly conspicuous as
the fruit dries.
On germination the cotyledons remain buried, the first pair
of foliage leaves are opposite, entire, broadly lanceolate, the
next few foliage leaves are pinnate with more and more leaflets.
The leaflets - often have sharply serrate margins.
The specimens studied at Manila, collected in March, 1918,
as well as the fruits sent to Washington and the seeds planted
at Los Banos, all come from a tree in the Singapore Botanic
Gardens. It is probable that it was grown from seeds taken
from the fruit sent to the former director, H. N. Ridley, " some
years" before 1908, collected by F. G. Penney in southern Siam,
especially as Ridley states in his original description of the
species that he then had seedlings in the botanic garden. If
planted, say in 1904, the tree would have been old enough to
bear fruit in 1917 when Professor Baker collected fruits.
POSSIBLE ECONOMIC USES OF THE KATINGA
If the katinga proves to be rather closely related to Chaetospermum
it is not improbable that, like Chaetospermum gluti-
XIII, C, 6 Swingle: Merillia, a new Rutaceous Genus 341
nosum ( Blanco) Swingle, it may be used as a stock upon which
to graft the commonly cultivated species of Citrus. Mr. Ridley
has called attention to the beauty of the wood of the katinga
and Mr. F. G. Penney secured enough of this wood in southern
Siam to make a much- admired set of furniture. The flowers are
very large and it is possible that this species would be worthy
of cultivation as an ornamental plant. At any rate it deserves
a place in every tropical and subtropical botanic garden and
arboretum.
ILLUSTRATIONS ·
[ The drawings of the fruit and seeds are from a nearly dry fruit preserved for BOrne months
in a refrigerator. Drawings by J. K. Santos.]
PLATE V. Merrillia caloxylon ( Ridley) Swingle.
A flowering branch from specimens taken from a tree growing
in the Singapore Botanic Gardens, showing young and
mature leaves and mature buds, one opening. Natural size.
VI. Merrillia caloxylon ( Ridley) Swingle.
a, a mature bud, natural size, drawn from the large bud shown
in Plate V soaked in water and partly opened.
b, pistil, X 2.
C, cross section of the ovary, X 20.
d, a seed, natural size.
e, a seed deprived of its paleae, showing the ariloid ridge at
the hilum.
f, cross section of a seed, X 2.
g, longitudinal section of a seed, X 2.
h, paleae from the seed, X 4.
i, cross section of a partly dry ripe fruit, natural size.
j, tangential section of a part of the pericarp, X 5, showing
the lacunae.
343
SWINGLE: MERRILLIA.] [ PHIL. JOURN. SCI., XIII, C, No. 6.
PLATE V. MERRILLIA CALOXYLON ( RIDLEY) SWINGLE.
SWINGLE: MERRILLIA.] [ PHIL. JOURN. SCI., XIII, C, No. 6.
e
b
f
d
a
c
i
g
h
PLATE VI. MERRILLIA CALOXYLON ( RIDLEY) SWINGLE.
Walter Tennyson Swingle
