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ILL 

UR Xoir< 

JUL 1 9 1982 



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UNIVERSITY Of lUlbiai&aiBRARY AT URBANA-CHAMPAIGN 



L161 O-1096 



FIELDIANA 
Botany 

Published by Field Museum of Natural History 
New Strii's, Xu. I 

FLORA COSTARICENSIS 

WILLIAM BURGER, Editor 

FAMILY #15, GRAMINEAE 
RICHARD W. POHL 



BIOLOGY 
101 



JUN 1 6 1981 



December 19, 1980 
Publication 1313 



Families of seed plants known or expected to occur in Costa Rica and adjacent 
areas, listed alphabetically and numbered according to the sequence of Engler's 
Syllabus der Pflanzenfamilien, edition 11, reworked by L. Diels (1936). 



200 

136 
67 

11 

64 

30 

117 

77 

184 

119 

19 

166 

4 

59 

185 

61 

127 

69 

48 

153 

74 

49 

194 

145 

133 

189 

24 

91 

38 

106 

12 

115 

154 

96 

114 

207 

36 

83 

203 

151 

138 

70 

40 

120 

72 

63 

42 

144 

169 

146 

161 

25 

208 

95 

186 

116 

168 

89 

84 

206 

92 

6 

1 

18 

16 

118 

112 

135 

32 

205 

88 

178 

156 

130 

143 

172 

23 



Acanthaceae 

Actinidiaceae 

Aizoaceae 

Alismataceae 

Amaranthaceae 

Amaryllidaceae 

Anacardiaceae 

Anonaceae 

Apocynaceae 

Aquifoliaceae 

Araceae 

Araliaceae 

Araucariaceae 

Aristolochiaceae 

Asclepiadaceae 

Balanophoraceae 

Balsammaceae 

Basellaceae 

Batidaceae 

Begoniaceae 

Berberidaceae 

Betulaceae 

Bignoniaceae 

Bixaceae 

Bombacaceae 

Boraginaceae 

Bromeliaceae 

Brunelliaceae 

Burmanniaceae 

Burseraceae 

Butomaceae 

Buxaceae 

Cactaceae 

Caesalpiniaeeae, 

see Leguminosae 
Callitrichaceae 
Campanulaceae 
Cannaceae 
Capparidaceae 
Caprifoliaceae 
Caricaceae 
Caryocaraceae 
Caryophyllaceae 
Casuarinaceae 
Celastraceae 
Ceratophyllaceae 
Chenopodiaceae 
Chloranthaceae 
Cistaceae 
Clethraceae 
Cochlospermaceae 
Combretaceae 
Commelinaceae 
Compositae 
Connaraceae 
Convolvulaceae 
Coriariaceae 
Cornaceae 
Crasaulaceae 
Cruciferae 
Cucurbitaceae 
Cunoniaceae 
Cupressaceae 
Cycadaceae 
Cyclanthaceae 
Cyperaceae 
Cyrillaceae 
Dichapetalaceae 
Dillemaceae 
Dioscoreaceae 
Dipsacaceae 
Droseraceae 
Ebenaceae 
Elaeagnaceae 
Elaocarpaceae 
Elatinaceae 
Ericaceae 
Eriocaulaceae 



102 


Erythroxylaceae 


82 


Papaveraceae 


113 


Euphorbiaceae 


150 


Pasaifloraceae 


96 


Fabaceae, 


195 


Pedal iaceae 




see Leguminosae 


66 


Phytolaccaceae 


50 


Fagaceae 


5 


Pinaceae 


148 


Flacourtiaceae 


41 


Piperaceae 


82 


Fumariaceae, 


171 


Pyrolaceae 




see Papaveraceae 


201 


Plantaginaceae 


45 
183 


Garryaceae 
Gentianaceae 


176 
3 


Plumbaginaceae 
Podocarpaceae 


99 


Geraniaceae 


54 


Podostemonaceae 


198 


Gesneriaceae 


187 


Polemoniaceae 


7 


Gnetaceae 


111 


Polygalaceae 


15 


Gramineae 


62 


Polygonaceae 


142 


Guttiferae 


26 


Pontederiaceae 


29 


Haemodoraceae 


68 


Portulacaceae 


165 


Halorrhagaceae 


9 


Potamogetonaceae 


93 


Hamamelidaceae 


175 


Primulaceae 


81 


Hernandiaceae 


55 


Proteaceae 


124 


Hippocastanaceae 


158 


Punicaceae 


121 


Hippocrateaceae 


140 


Quiinaceae 


101 


Humiriaceae, 


60 


Rafflesiaceae 




see Linaceae 


73 


Ranunculaceae 


13 


Hydrocharitaceae 


86 


Resedaceae 


188 


Hydrophyllaceae 


128 


Rhamnaceae 


142 


Hypericaceae, 


160 


Rhizophoraceae 




see Guttiferae 


94 


Rosaceae 


123 


Icacinaceae 


202 


Rubiaceae 


33 


Iridaceae 


104 


Rutaceae 


47 


Juglandaceae 


126 


Sabiaceae 


27 


Juncaceae 


44 


Salicaceae 


97 


Krameriaceae 


125 


Sapindaceae 


191 


Labiatae 


177 


Sapotaceae 


43 


Lacistemaceae 


90 


Saxifragaceae 


80 


Lauraceae 


193 


Scrophulariaceae 


159 


Lecythidaceae 


105 


Simarubaceae 


96 


Leguminosae 


192 


Solanaceae 


20 


Lemnaceae 


122 


Staphyleaceae 


199 


Lentibulariaceae 


134 


Sterculiaceae 


28 


Liliaceae 


180 


Styracaceae 


101 


Linaceae 


179 


Symplocaceae 


152 


Loasaceae 


2 


Taxaceae 


182 


Loganiaceae 


141 


Theaceae 


58 


Loranthaceae 


173 


Theophrastaceae 


157 


Lythraceae 


155 


Thymelaeaceae 


76 


Magnoliaceae 


131 


Til iaceae 


108 


Malpighiaceae 


85 


Tovariaceae 


132 


Malvaceae 


109 


Trigoniaceae 


37 


Marantaceae 


14 


Triuridaceae 


139 


Marcgraviaceae 


100 


Tropaeolaceae 


196 


Martyniaceae 


149 


Turneraceae 


21 


Mayacaceae 


8 


Typhaceae 


163 


Melastomataceae 


51 


Ulmaceae 


107 


Mel iaceae 


167 


Umbelliferae 


75 


Menispermaceae 


53 


Urticaceae 


96 


Mimosaceae, 


204 


Valerianaceae 




see Leguminosae 


31 


Velloziaceae 


79 


Monimiaceae 


190 


Verbenaceae 


170 


Monotropaceae 


147 


Violaceae 


52 


Moraceae 


129 


Vitaceae 


87 


Moringaceae 


110 


Vochyaiaceae 


24 


Musaceae 


22 


Xyridaceae 


46 


Myricaceae 


35 


Zingiberaceae 


78 


Myristicaceae 


103 


Zygophyllaceae 


174 


Myrsinaceae 






162 


Myrtaceae 






10 


Najadaceae 






65 


Nyctaginaceae 






71 


Nymphaeaceae 






137 


Ochnaceae 






56 


Olacaceae 






181 


Oleaceae 






164 


Onagraceae 






57 


Opiliaceae 






09 


Orchidaceae 






197 


Orobanchaceae 






98 


Oxalidaceae 






17 


Palmae 








JUN161981 



FLORA COSTARICENSIS 
FAMILY #15, GRAMINEAE 



FIELDIANA 
Botany 

Published by Field Museum of Natural History 



New Series, No. 4 



FLORA COSTARICENSIS 

WILLIAM BURGER, Editor 

Curator, Vascular Plants 

Field Museum of Natural History 



FAMILY #15, GRAMINEAE 
RICHARD W. POHL 

Research Associate in Botany 
Field Museum of Natural History 
Distinguished Professor 
Botany, Iowa State University 



Accepted for publication Nov. 20, 1978. 

This publication was supported in part by NSF grant DEB74-08575. 

December 19, 1980 

Publication 1313 



Library of Congress Catalog Card Number: 79-55875 

US ISSN 0015-0746 
PRINTED IN THE UNITED STATES OF AMERICA 



CONTENTS 

Acknowledgements 1 

Abbreviations 2 

Gramineae (Poaceae), Grass Family 3 

Classification of the Grass Family 7 

Index . .596 



ACKNOWLEDGEMENTS 

Working toward the completion of a taxonomic treatment of the 
grasses of Costa Rica, field work began in 1966. It has been aided by so 
many people and agencies that it is difficult to know how to express 
appreciation to them all. Financial support for all of the field work and 
for expenses connected with herbarium study were furnished by the 
National Science Foundation under grants GB-7307X and GB-32085. 
The author received salary for six months in 1968 under a Faculty 
Improvement Leave Grant from Iowa State University. The facilities 
of the Iowa State University Herbarium, supported by the Sciences 
and Humanities Research Institute, were used throughout the term of 
my studies. 

My study of Costa Rican grasses began while I was an instructor in a 
course on tropical grasses given by the Organization for Tropical 
Studies during the summer of 1966. The organization has since that 
time furnished aid in many ways, including logistic support and the use 
of its bases in Costa Rica. My special thanks go to Sr. Jorge Cam- 
pabadal, Resident Director of the O.T.S. in San Jose, for the many 
ways in which he made my field work easier and more productive. Dr. 
Rafael Rodriguez C. of the Department of Biology of the University of 
Costa Rica furnished laboratory space and equipment for the 1968- 
1969 year, and has given generously of his time and counsel during the 
entire time of the field work. The Museo Nacional de Costa Rica and 
Sr. Luis Diego Gomez P. furnished facilities, the use of the herbarium, 
and the use of a field vehicle. The family of Mr. Werner Hagnauer of 
Finca la Pacifica at Canas furnished not only food, shelter, and a kindly 
atmosphere, but much sagacious counsel on field travel in Guanacaste. 
Dr. Gerrit Davidse, currently of the Missouri Botanical Garden in St. 
Louis, was my field companion in Costa Rica from June, 1968 to May, 
1969. Much of the success of the field program is due to his indefatiga- 
ble efforts. He is also responsible for many of the hundreds of chromo- 
some counts that we obtained from Central American grasses, which 
are reported in the text. 



2 FIELDIANA: BOTANY 

Field Museum has furnished access to its herbarium and library, and 
allowed the use of its field vehicles in Costa Rica. My special thanks are 
due to Louis Williams and William Burger of the Museum. During my 
many visits to the U.S. National Herbarium, Dr. Thomas Soderstrom 
and Dr. Cleofe Calderon furnished facilities, access to literature, and 
aid in identifications. 

Finally, like all field biologists in Costa Rica, I owe a great deal to 
the friendly and courteous people of that beautiful land. They have 
helped in many ways, ranging from extricating my jeep from a ditch to 
offering interest and information about the plants that I was studying. 

ILLUSTRATIONS 

The majority of the illustrations of grasses in this publication are the 
work of Judy Appenzeller LaMotte (JEA). Most of the remainder are 
taken from the illustrations of various publications of Agnes Chase and 
A. S. Hitchcock, the originals of which are now in the Hunt Center for 
Botanical Documentation and are used with the kind permission of that 
institution. Scale lines for spikelets are 1 mm. long; for larger 
structures, 1 cm. long. 

ABBREVIATIONS 

BREM tlbersee-Museum, Bremen, Federal Republic of Germany 
CATIE Centro Agronomico Tropical de Investigation y Ensenanza, 

Turrialba 

CIA Carretera Interamericana (Interamerican Highway) 
CR Herbario Nacional, Museo Nacional de Costa Rica, San Jose 

F Field Museum of Natural History 

IICA Institute Interamericana de Ciencias Agricolas, Turrialba 
ISC Iowa State University Herbarium, Ames, Iowa 
JEA Judy Appenzeller LaMotte, artist 
US United States National Herbarium, Smithsonian Institution, 

Washington, D.C. 



GRAMINEAE (POACEAE). GRASS FAMILY 

REFERENCES: N. L. Bor, The grasses of Burma, Ceylon, India and 
Pakistan (excluding Bambuseae). XVIII + 767 pp. Pergamon Press. 
London. 1960. A. Burkart (ed.) & collaborators, Flora Ilustrada de 
Entre Rios (Argentina), Parte II: Gramineas. V + 551 pp. Coleccion 
Cientifica del I.N.T.A., Tomo VI, II. Buenos Aires. 1969. E. G. 
Camus, Les Bambusees. Texte, 215 pp. Lechevalier. Paris. 1913. + 
Atlas of 101 plates. Not dated. W. D. Clayton, Flora of Tropical East 
Africa, Gramineae, Part 1:1-176. Government Bookshops. London. 
1970. E. Fournier, Mexicanas Plantas, Pars Secunda. Gramineae. 160 
pp. Typographeo Reipublicae. Paris. 1881. J. S. Gamble, The Bam- 
buseae of British India, Ann. Roy. Bot. Gard. (Calcutta). 1896. Re- 
print by Micro Methods Ltd. & Johnson Reprint Corp. 1966. A. S. 
Hitchcock, The grasses of Central America, Contr. U.S. Natl. Herb. 
23(9):XVI + 557-762. U.S. Govt. Printing Office. Washington, D.C. 
1930. A. S. Hitchcock, Manual of the grasses of the West Indies, Misc. 
Publ. 243, U.S. Dept. Agric. 439 pp. Govt. Printing Office. 
Washington, D.C. 1936. C. E. Hubbard, Flora of Tropical Africa. (A. 
W. Hill, ed.) 10(1): 192 pp. L. Reeve. Ashford. 1937. H. Jacques-Felix, 
Les Graminees (Poaceae) D' Afrique Tropicale I. Generalites, 
Classification Description des Genres. XI + 345 pp. Ins. Recherches 
Agron. Trop. Paris. 1962. A. S. Maroto, Los Forrajes de Costa Rica. 
606 pp. Universidad de Costa Rica. San Jose. 1955. F. A. McClure, 
Genera of bamboos native to the New World (Gramineae: Bam- 
busoideae, Smithsonian Contr. Bot. 9:XI + 148. Smithsonian Inst. 
Press. Washington, D.C. 1973. New York Bot. Gard. ed. 1912-1939. 
North American Flora 17:77-638, Family Poaceae. Parts 1, 2, 3 by G. 
V. Nash, 1912-15 pp. 77-288; Parts 4, 5, 6, 7 by A. S. Hitchcock, 
1935-37, pp. 289-354; Part 8, by A. S. Hitchcock, J. R. Swallen, & 
Agnes Chase, 1939, pp. 543-638. H. Pittier, Ensayo sobre Plantas 
Usuales de Costa Rica, ed. 2. Revised by R. Rodriguez C. 264 pp. + 50 
plates. Editorial Universitaria. San Jose. 1957. B. Rosengurtt, B. R. 
Arrillaga de Maffei, & P. Izaguirre de Artucio. Gramineas Uruguayas. 



4 FIELDIANA: BOTANY 

VII + 489 pp. Universidad de la Republica. Montevideo. 1970. 0. 
Stapf, Flora of Tropical Africa. (D. Prain, ed.) IX. Gramineae 
(Maydeae-Paniceae). VI + 1,132pp. L. Reeve. London 1917-1934. G. 
L. Stebbins, Jr., & B. Crampton, A suggested revision of the grass 
genera of North America, Recent Advances in Botany, pp. 133-145. 
1961. J. R. Swallen, The grasses of the Yucatan Peninsula, Appendix 
to Contr. Amer. Archaeol., No. 12. Carnegie Inst. Wash. Publ. 
436:323-355. 1934. J. R. Swallen, Botany of the Maya Area: Miscel- 
laneous Papers IX: The grasses of British Honduras and the Peten, 
Guatemala, Carnegie Inst. Wash. Publ. 461:141-189. 1936. J. R. Swal- 
len, Flora of Panama: Gramineae, Ann. Missouri Bot. Gard. 30:104- 
280. 1943. J. R. Swallen, Flora of Guatemala, Part II: Grasses of 
Guatemala (Bamboos by F. A. McClure), Fieldiana, Bot. 24, Pt. II:IX 
+ 390 pp. 1955. 

Mostly herbaceous plants, occasionally shrubby or treelike, as in the bamboos. Root 
systems fibrous, mostly lacking in characters of systematic importance, in large part of 
adventitious origin from the basal nodes, the primary root soon dying. Stems conspicu- 
ously jointed, mostly with hollow internodes and solid nodes; aerial stems (culms) mostly 
terminating in inflorescences; plants also producing young vegetative stems (innova- 
tions) from the base. Plants variously clump-forming (caespitose) or with stolons or 
rhizomes. Branches ordinarily 1 per node, the base subtended by a highly modified 
bracteal leaf, the prophyllum, attached to the base of the branch and tending to hold 
together the main stem and the branch. Foliage leaves alternate, spaced 180 deg. apart 
on the stem. Each leaf consists of three major parts, these being the sheath that sur- 
rounds the internode and which usually has overlapping edges; the ligule, a small mem- 
branaceous or hairy rim or projection at the juncture of the sheath and the leaf blade; 
and the usually flat, linear, parallel- veined leaf blade. In addition to these structures, the 
following are sometimes seen. The flange, or dewlap, is a triangular outpouched area 
between the summit of the sheath and the blade proper. It permits upward and down- 
ward motion of the blade. The collar is the line of union between the lower surface of the 
blade and the sheath. Auricles are rounded or pointed projections of the base of the blade 
or the summit of the sheath. In bamboos and their relatives and a few other grasses, a 
narrow stalk is intercalated between the base of the blade proper and the summit of the 
sheath. This is the pseudopetiole, morphologically a portion of the leaf blade and not a 
true petiole. 

Grass inflorescences are extremely variable, and difficult to confine to a simple system 
of nomenclature. Since grasses do not have naked individual flowers, the terminology 
ordinarily used for inflorescences does not well fit their flowering structures. While 
authors have ordinarily used standard inflorescence names in describing grasses, it 
should be borne in mind that such usage always implies that the flowering unit is a 
spikelet, not an individual flower. I have used the terms panicle, spike, and raceme in the 
usual sense, but have added a new term, RAME, to indicate an unbranched axis that 
bears both sessile and pedicellate spikelets. This term is convenient to indicate the 
flowering axes of the Tribe Andropogoneae, where one of each pair of spikelets may be 
sessile and the other pedicellate. Inflorescences are often terminal on the culms of 



BURGER: FLORA COSTARICENSIS 5 

grasses, but in many cases axillary ones are also produced. In one genus (Pariana) 
naked inflorescences arise from the soil level, and in a few grasses (C Moris chl&ridea, 
the genus Amphicarpum) entirely subterranean inflorescences occur. 

The spikelet is the basic unit of the grass inflorescence. It is a small axis (rachilla) 
bearing alternate overlapping bracts distichously. It is never secondarily branched, 
thereby differing from other inflorescence structures. Usually spikelets are borne on 
slender stalks, the pedicels. The lowermost two (rarely one) bracts of the spikelet 
(glumes) are sterile. 

Successive nodes of the rachilla above the glumes bear flowering units called florets. 
The floret consists of an outer bract, the lemma, attached to the rachilla itself, an inner 
bract, the palea, attached to the flower axis, and the included flower. The lemma and 
palea together are sometimes called the anthoecium (anthecium). The lemma may bear a 
projecting midrib, the awn. Rarely lateral nerves (vascular bundles) may also be ex- 
tended into awns, as in Aristida. The inner floral bract, the palea, is the homologue of 
the prophyllum found on vegetative parts of the plant. In spikelets with several florets, 
disarticulation often takes place at the apex of each rachilla internode, so that the 
disseminules are individual florets. In the Subfamily Panicoideae, in general, and in 
various other genera, the entire spikelet is shed from the plant as a unit. 

Grass flowers are very small, and lack a conspicuous perianth. The vestiges of the 
perianth are small fleshy or scale-like bodies called lodicules. Two lodicules are present 
in all the grass subfamilies with the exception of the Bambusoideae. They are placed at 
the base of the ovary on the side toward the lemma, and serve, by their rapid swelling, 
to force the lemma outward and permit the exposure of the anthers and stigmas at 
anthesis. The shape, number, and vasculation, or lack of it, of the lodicules are char- 
acteristic of the various subfamilies of the Gramineae. In the Subfamily Pooideae, the 
lodicules are more or less pointed, flattened except near the swollen base, and non- 
vascular. In the Subfamilies Chloridoideae, Oryzoideae, and Panicoideae, the lodicules 
are thick, fleshy, truncate, and possess vascular traces. In the Bambusoideae, three 
lodicules are ordinarily present. They are flat, ovate, pointed, and have conspicuous 
forking vascular traces. A great majority of grasses have three stamens, with elongated 
flexuous filaments and large, versatile anthers. A few isolated species have one or two 
anthers, and the Bambusoideae ordinarily have six, or rarely other numbers. The 
gynoecium in most grasses, with the exception of the Bambusoideae, has two style 
branches bearing enlarged plumose stigmas. A third carpel is represented only by a 
vascular bundle in the ovary wall. In the Bambusoideae, most species have a single style 
bearing three rather small stigmas. With rare exceptions, grasses have some or all of the 
flowers perfect. A few monoecious or dioecious grasses occur in widely disparate groups 
of grasses. 

The fruit in grasses is generally a caryopsis, a single-seeded dry indehiscent grain 
with the pericarp and seed united. In a few genera, notably Sporobolus, the pericarp 
gelatinizes and separates from the seed. In the bamboos, various types of specialized 
grass fruits occur. 

While true grass spikelets never rebranch, some bamboos and their herbaceous rela- 
tives have complex bracted structures which branch secondarily into the true spikelets. 
Such structures are designated as pseudospikelets. 

The duration of the life of grasses is usually designated as annual or 
perennial. While this distinction is fairly usable in the temperate zone, 



6 FIELDIANA: BOTANY 

it does not work well in the tropics, where frost or drought does not 
often occur to terminate the life of the individual. In instances where it 
seems impossible to determine the life span of plants of a species, I 
have indicated this by the statement "duration indefinite." In the 
tropics, stoloniferous grasses frequently fall into this category. 

Measurements given in this work are derived primarily from Cen- 
tral American specimens. It is possible that material from other areas 
might yield larger or smaller values. Plane shapes of structures are 
designated according to the International Association for Plant Tax- 
onomy chart (Taxon 11:145-156. 1962). According to this system, a 
shape is designated by a general class, followed by a ratio indicating 
the length to width proportions, as for example: ovate 4:1; obovate 
3-7:1. 

The abbreviations CIA, for Carretera Interamericana (the Pan 
American Highway), and P.&D., for collections of Pohl & Davidse, are 
often used in the discussions under the species. 

Chromosome numbers cited in the text are mostly derived from 
counts made by the author and Dr. Gerrit Davidse and published 
in the following series of papers: R. W. Pohl & G. Davidse, Chromo- 
some numbers of Costa Rican grasses, Brittonia 23:293-324. 1971. G. 
Davidse & R. W. Pohl, Chromosome numbers and notes on some Cen- 
tral American grasses, Canad. J. Bot. 50:273-283. 1972; Chromosome 
numbers, meiotic behavior, and notes on some grasses from Central 
America and the West Indies, Canad. J. Bot. 50:1441-1452. 1972; 
Chromosome numbers, meiotic behavior, and notes on tropical Ameri- 
can grasses (Gramineae), Canad. J. Bot. 52:317-328. 1974. 



CLASSIFICATION OF THE GRASS FAMILY 

For many years, the standard classification of the Gramineae used in 
most works of American origin was that of A. S. Hitchcock. This 
system featured the use of two large subfamilies, the Festucoideae and 
Panicoideae, and a rather limited number of inclusive tribes. Studies in 
grass morphology, anatomy, cytology, ecology, and physiology indi- 
cate that this system did not make sufficient allowance for the wide- 
spread and frequent occurrence of convergent evolution in external 
form. A number of newer systems of classification, utilizing a much 
wider range of data in the formulation of the major categories, have 
been proposed in recent years. The system used for this work is based 
largely on the one proposed for the American temperate zone elements 
of the family by G. L. Stebbins and Beecher Crampton. I have 
modified this system in detail, but the general outline follows the work 
of the above authors. While the system has much higher phylogenetic 
and predictive value than older arrangements, it does not lend itself to 
use for routine identification. I have therefore constructed artificial 
keys to assist in identification, and the arrangement in the text is 
strictly alphabetical. 

The following brief summary will serve to indicate the principal 
characteristics of each of the six subfamilies recognized in this treat- 
ment, and indicate the Costa Rican genera belonging to each one. 

SUBFAMILY I. BAMBUSOIDEAE 

This subfamily includes the bamboos and a number of herbaceous 
grasses, mostly found in moist forests of the tropics, which resemble 
the bamboos in their leaf epidermal and cross-sectional anatomy, the 
number and nature of lodicules, the number of stamens and stigmas. 
The bamboos are readily recognized by their woody stems, and all of 
these grasses possess at least short pseudopetioles. The following gen- 
era occur in Costa Rica: 

Woody bamboos. Arthrostylidium, Aulonemia, Bambusa, 



FIELDIANA: BOTANY 

Chusquea, Elytrostachys, Merostachys, Rhipidocladum, Swallen- 
ochloa. A number of other genera are cultivated, including species of 
Phyllostachys, Yushania, and Bambusa. 

Herbaceous bamboos: Cryptochloa, Lithachne, Olyra, Pariana, 
Raddia, Pharus, Streptochaeta, Streptogyna. 

The treatment of the bamboos in this work is necessarily tentative. 
Many of the species bloom only after long intervals of years, and some 
have never been observed to bloom in our area. Much more field and 
herbarium work will have to be done before a definitive treatment of 
the Central American bamboos can be produced. 

SUBFAMILY II. ORYZOIDEAE 

This is a relatively small subfamily, allied to the bambusoids by 
anatomical characteristics and chromosome numbers. Their spikelets 
have very reduced or vestigial glumes, usually appearing as a minute 
cupule at the apex of the pedicel. There is only one fertile floret. All are 
plants of wet ground or water. The following genera occur in Costa 
Rica: Leersia, Luziola, Oryza. 

SUBFAMILY III. POOIDEAE (FESTUCOIDEAE) 

This is a large subfamily, containing many of the grasses of the 
temperate and cold regions of the world. In Central America, rela- 
tively few of them occur, and these mostly at high elevations. They are 
characterized by rather simple leaf anatomy, reduced embryo struc- 
ture, and the possession of large chromosomes in multiples of seven. 
The following genera occur in Costa Rica, some of them as introduc- 
tions in upland pastures: Aciachne, Agropyron, Agrostis, Aira, 
Anthoxanthum, Avena, Briza, Brachy podium, Bromus, Calama- 
grostis, Cinna, Cynosurus, Dactylis, Deschampsia, Festuca, Gly- 
ceria, Hierochloe, Holcus, Lolium, Lorenzochloa, Nassella, Phalaris, 
Poa, Polypogon, Secale, Stipa, Triniochloa, Trisetum, Vulpia. 

SUBFAMILY IV. ARUNDINOIDEAE 

This subfamily contains numerous large, reedlike grasses, often 
with plumelike, fuzzy panicles. Other genera included here are placed 
largely on anatomical grounds. Costa Rican representatives are: 
Aristida, Arundo, Cortaderia, Danthonia, Gynerium, Orthoclada, 
Phragmites, Zeugites. 

SUBFAMILY V. CHLORIDOIDEAE (ERAGROSTOIDEAE) 

This is an abundant subfamily of warm climates. They are funda- 
mentally characterized by microscopic characters, including the elabo- 



BURGER: FLORA COSTARICENSIS 9 

rately structured leaf cross-section, featuring a number of quasi- 
independent units, the cells of each radiating around a single vascular 
bundle. In many, the lemmas have three strong vascular bundles, in 
contrast to the five or more faint bundles in lemmas of most pooid 
grasses. The following genera occur in Costa Rica, mostly at low or 
middle elevations: Aegopogon, Bouteloua, Chloris, Cynodon, Dac- 
tyloctenium, Eleusine, Eragrostis, Gouinia, Gymnopogon, Jouvea, 
Leptochloa, Muhlenbergia, Pentarraphis, Pereilema, Spartina, Spor- 
obolus, Triplasis, Uniola, Zoysia. 

SUBFAMILY VI. PANICOIDEAE 

This is by far the largest subfamily of warm climate grasses, forming 
a significant portion of the grass cover in tropical regions. Spikelets, 
with rare exceptions, are dorsally compressed, have a single perfect 
flower, and disarticulate below the glumes. Genera occurring in Costa 
Rica are the following: Acroceras, Andropogon, Anthephora, Arthra- 
xon, Arundinella, Axonopus, Bothriochloa, Brachiaria, Cenchms, 
Chaetium, Coelorachis, Coix, Cymbopogon, Diectomis, Digitaria, 
Echinochloa, Echinolaena, Eremochloa, Eriochloa, Eriochrysis, 
Euclasta, Hackelochloa, Homolepis, Hymenachne, Hyparrhenia, 
Hypogynium, Ichnanthus, Imperata, Isachne, Ischaemum, Ixo- 
phorus, Lasiacis, Leptocoryphium, Melinis, Mesosetum, Oplis- 
menus, Panicum, Paratheria, Paspalidium, Paspalum, Penni- 
setum, Polytrias, Pseudechinolaena, Rhynchelytrum, Rottboellia, 
Saccharum, Sacciolepis, Schizachyrium, Setaria, Sorghastrum, Sor- 
ghum, Stenotaphrum, Thrasya, Trachypogon, Tripsacum, Urochloa, 
Vetiveria, Zea. 

MASTER KEY 

la. Culms at least 2 m. tall, woody and perennial; foliage leaves usually borne on 

secondary branches; rarely blooming KEY I 

Ib. Culms herbaceous, usually less than 2 m. tall; foliage leaves on main culms as well 

as branches; blooming annually 2 

2a. All or some spikelets borne partially or completely concealed, in spiny burs, 
or bony rachis joints, or bead-like or horn-like structures, or detachable fasci- 
cles of hard bracts, or completely hidden in leaf sheaths with only the stamens 

and stigmas visible KEY II 

2b. Spikelets borne in the open, in panicles, racemes, rames, or spike-like 

inflorescences 3 

3a. Leaf blades separated from sheaths by slender pseudopetiole, 5 mm. -several cm. 

long KEY III 

3b. Leaf blades attached directly to sheaths, or with short pseudopetioles not more 
than 1-3 mm. long 4 



10 FIELDIANA: BOTANY 

4a. Spikelets disarticulating above the glumes which remain attached to pedicels 

as visible bracts KEY IV 

4b. Spikelets disarticulating completely from the pedicels, no glumes remaining 

on the plant, or at the most a minute nerveless cupule 5 

5a. Spikelets all falling as single units, without attached accessory structures 

KEY V 

5b. Spikelets, or some of them, falling in clusters or with attached rachis, pedicels, or 
sterile, bristle-like branches KEY VI 

KEY I 

GIANT GRASSES; CULMS 2-30 M. TALL, OFTEN WOODY OR SOLID 

la. Culm internodes solid, without central lumen 2 

Ib. Culm internodes with small or large central lumen 4 

2a. Leaf blades 1-several m. long, borne on main culm; culms pithy, not ex- 
tremely woody 3 

2b. Leaf blades usually less than 20 cm. long, mostly borne on small lateral 

branches, main culms naked or bearing bladeless sheaths Chusquea 

3a. Leaf blades distributed along culms; spikelets single-flowered, disarticulating 
below glumes; cultivated crop (sugar cane; cana de azucar); pith sweet 

Saccharum officinarum 

3b. Leaf blades borne in a large, fan-shaped cluster at the apex of culm; spikelets 
2-flowered, disarticulating above the glumes; wild plants, usually growing on river 

banks; pith not sweet Gynerium sagittatum 

4a. Leaf blades 1-2 m. long, cordate-clasping at base, borne on main culm, often 
yellow-striped; culms thin-walled; plants cultivated for ornament, rarely 

escaping to the wild Arundo donax 

4b. Leaf blades usually 20 cm. long or shorter, not cordate-clasping, mostly with 

short pseudopetioles; wild or cultivated plants 5 

5a. Culms with thorny branches Bambusa 

5b. Culms lacking thorny branches 6 

6a. Culms barely woody, internodes slender (1 cm. or less), green, and soft (can 

be crushed with the fingers) 7 

6b. Culms definitely woody, of various diameters 9 

7a. Culms with glistening, viscid band at nodes; plants rarely blooming 

Aulonemia 

7b. Culms not viscid; plants annual bloomers 8 

8a. Spikelets alike, black and shiny when mature, placed at an angle to 
pedicel; disarticulation below glumes; leaf blades sessile, without pseudo- 
petioles Lasiacis 

8b. Spikelets unisexual, of 2 kinds, not black, aligned with pedicel; disarticulation 

above glumes; leaf blades with short pseudopetiole Olyra 

9a. Bamboos of various habits, in forested or savanna habitats below 3,000 m. eleva- 
tion; lumen of internodes usually large and with definite boundary membrane; 

branches 2-many per node 10 

9b. Small, shrubby bamboos of paramos above 3,000 m. elevation; central lumen of 



BURGER: FLORA COSTARICENSIS 11 

culm internodes small, lacking definite boundary membrane; branches stiff and 

erect, usually 3-5 per node Suxillenochloa 

lOa. Branches at midculm nodes numerous, arising from edges of flat, triangular 

plate-like meristem that is closely appressed to main culm 11 

lOb. Branches at midculm nodes not arising from flat plate, of varying number . 12 
lla. Midculm sheaths with a narrow reflexed blade that is constricted at its base and 

much narrower than sheath apex Merostachys 

lib. Midculm sheaths with an erect blade that is as wide as the sheath apex and not 

constricted at the base Rhipidocladum 

12a. Primary midculm branches solitary, soon branched near the base; auricular 
bristles very prominent, up to 8 cm. long on the main culm sheaths 

Elytrostachys 
12b. Primary midculm branches 2-several per node; auricular bristles short . 13 

13a. Branches 3-many per node, arising above the node at the apex of a prominent bulge 
that continues down to the node; internodes cylindrical in cross-section; wild plants 

Arthrostylidium 

13b. Primary branches usually 2 per node; internodes D-shaped in cross-section; culti- 
vated bamboos, used for hedges, banana props, etc Phyllostachys 



KEY II 

GRASSES WITH VARIOUSLY CONCEALED OR HIGHLY MODIFIED SPIKELETS 

la. Low, stoloniferous grass of mountain pastures; spikelets concealed within sheaths, 

only stigmas and stamens protruding Pennisetum clandestinum 

Ib. Grasses of various statures; spikelets not all concealed in leaf sheaths 2 

2a. Inflorescence a spike of densely spiny, readily detached burs, each concealing 

1-several spikelets Cenchrus 

2b. Inflorescence not bearing spiny burs 3 

3a. Inflorescence an unbranched spike bearing fascicles of coriaceous flat bracts which 
conceal spikelets, fascicles readily detached from zigzag rachis 

Anthephora hermaphrodita 

3b. Inflorescence rachis without detachable fascicles 4 

4a. Low stoloniferous or rhizomatous widely spreading plants 5 

4b. Plants not stoloniferous or rhizomatous; culms erect 6 

5a. Sheaths strongly flattened and keeled; plants stoloniferous on moist soil; spikelets 
sunken into one side of flattened, corky, club-shaped erect rachis; spikelets 

perfect-flowered Stenotaphrum secundatum 

5b. Sheaths not keeled; plants stoloniferous or rhizomatous, forming mats or mounds 
on coastal sand dunes or mud flats; plants dioecious; pistillate plants bearing rigid, 

pointed horns containing caryopses, in clusters at tips of the culms Jouvea 

6a. Pistillate spikelets borne in single spheroidal beads on tips of axillary pedun- 
cles; staminate inflorescence a short cluster of spikelets protruding from 

opening of bead Coix laeryma-jobi 

6b. Pistillate spikelets borne in exposed spikes or on axillary cobs concealed in 

leaf sheaths, never in beadlike structures 7 

7a. Staminate spikelets borne on terminal panicle; pistillate spikelets borne on a thick 



12 FIELDIANA: BOTANY 

axillary spike (cob), completely covered with leaf sheaths, styles protruding as 

"silks" Zea mays 

7b. Staminate and pistillate spikelets borne together on 1-several spikes, basal portion 
of each spike composed of a series of hard, bony internodes, each containing a 
single pistillate spikelet, internodes separating when mature; terminal portion of 
spike with flattened, non-disarticulating rachis, each node bearing a pair of stami- 
nate spikelets Tripsacum 

KEY III 

LEAF BLADES WITH PSEUDOPETIOLES AT LEAST 5 MM. LONG 

la. Spikelets laterally compressed, with 2-many florets 2 

Ib. Spikelets not compressed, with a single floret 3 

2a. Spikelets 2-flowered; flowers perfect Orthoclada laxa 

2b. Spikelets several-many flowered; lowermost flower pistillate, the others 

staminate Zeugites 

3a. Veins of leaf blades diverging from midrib, running straight to lateral leaf margins; 

lemmas awnless; inflorescence a panicle Pharus 

3b. Veins of leaf blades running from base to tip of blades, parallel to midrib; spikelets 
with a long, coiled awn; inflorescence a spike Streptochaeta 

KEY IV 

SPIKELETS WITH I-MANY FLORETS; GLUMES EVIDENT, WITH A MIDRIB; 
DlSARTICULATION ABOVE THE GLUMES, WHICH REMAIN ON THE PEDICELS 

la. Spikelets with 1 floret 2 

Ib. Spikelets with 2-many florets, some of which may be staminate or sterile ... 23 

2a. Spikelets unisexual, the two kinds different in appearance 3 

2b. Spikelets with perfect flowers, all alike 7 

3a. Leaf blades with veins running from base to tip 4 

3b. Leaf blades broad, with veins running from midrib to lateral margins; fertile lemma 

bearing hooked hairs Pharus 

4a. Fertile floret broad and flat at apex, obpyramidal, hard and bony 

Lithachne pauciflora 

4b. Fertile floret acute-tipped, elliptical 5 

5a. Inflorescence with usually less than 5 spikelets; low grasses of rain forests, less 
than 30 cm. tall; leaf blades short, crowded; leafy culms resembling the pinnately 

compound leaves of some legumes 6 

5b. Inflorescence with many spikelets; plants small or up to 3-4 m. tall; leaves not 

crowded, lanceolate to linear Olyra 

6a. Leaf blades hirsute Raddia costaricensis 

6b. Leaf blades glabrous Cryptochloa 

7a. Dwarf paramo plants, less than 5 cm. tall, forming flat, circular mats, with stiff, 
short leaves less than 1.5 cm. long; inflorescences of 1-7 spikelets, mostly hidden 
among the leaves 8 



BURGER: FLORA COSTARICENSIS 13 

7b. Plants large or small, of various habitats; inflorescences with many spikelets, sup- 
ported above foliage on peduncle 9 

8a. Leaf blades sharp-pointed; first glume 3-5-nerved Aciachne pulvinata 

8b. Leaf blades with boat-shaped tips; first glume 1-nerved 

Muhlenbergia calcicola 

9a. Floret hard, smooth, usuaUy awned 10 

9b. Floret soft-textured, awned or awnless 16 

lOa. Floret awnless, laterally compressed, with 2 minute rudimentary florets at- 
tached below it and closely appressed to it, the three falling as a unit from 

glumes Phalaris 

lOb. Floret awned, without rudimentary florets below, terete or nearly so . . 1L 

lla. Lemma bearing 3 awns, lateral 2 often smaller Aristida 

lib. Lemma bearing single awn 12 

12a. Awn attached to back of lemma below tip Triniochloa stipoides 

12b. Awn attached at tip of lemma 13 

13a. Palea exposed between edges of lemma Lorenzochloa 

13b. Palea concealed by overlapping margins of cylindrical lemma 14 

14a. Floret plump, swollen near apex, the readily deciduous awn attached eccen- 
trically Nassella 

14b. Floret slender-cylindrical, firmly attached awn attached at center of apex . 15 
15a. Awn glabrous, curved, not strongly twisted above base; in savannas at low eleva- 
tions Aristida 

15b. Awn hairy below, straight but geniculate, strongly twisted above the base; upper 

elevations in mountains Stipa icku 

16a. Fertile spikelets surrounded by cluster of bristles (abortive spikelets) 

Pereilema 
16b. Spikelets not surrounded by bristles 17 

17a. Inflorescence a panicle 19 

17b. Inflorescence of several-many 1-sided spikes or racemes 18 

18a. Stoloniferous or rhizomatous plants; spikes digitate; lemmas awnless; com- 
mon weed Cynodon 

18b. Tufted plants; spikes racemose; lemmas awned; rare, Boruca 

Gymnopogon fastigiatus 

19a. Both glumes longer than floret 20 

19b. One or both glumes shorter than floret 21 

20a. Rachilla prolonged behind palea of the floret as a thin, often hairy bristle; 

callus hairs often long and abundant, rarely short or scanty 58 

20b. Rachilla not prolonged behind palea; callus hairs usually short or minute . 59 

21a. Awn arising from the back of lemma below tip Triniochloa stipoides 

21b. Awn absent or arising from tip of lemma 22 

22a. Lemmas 1-nerved, awnless; ovary wall gelatinous and swollen when wet, the 

seed extruding from burst ovary Sporobolux 

22b. Lemmas 3-nerved, usually awned; ovary wall not becoming gelatinous, seed 

not extruding Muhlenbergia 

23a. Inflorescence a single balanced or 1-sided spike or raceme 24 



14 FIELDIANA: BOTANY 

23b. Inflorescence a panicle, or group of spikes or racemes borne on common pedun- 
cle 29 

24a. Florets becoming entangled into single group by the elongated, stiff, 

spirally-coiled styles; stigmas 3 Streptogyna americana 

24b. Florets not becoming entangled by styles; stigmas 2 25 

25a. Spikelets on short, erect, hairy pedicels Brachypodium mexicanum 

25b. Spikelets sessile 26 

26a. Spikelets 2-flowered; keels of lemmas with row of short, stiff, spreading hairs; 

cultivated, upper elevations, rare Secale cereale 

26b. Spikelets with more than 2 flowers; keels of lemmas without spreading 

hairs 27 

27a. Spikelets placed edgewise to rachis, only exterior glume present; flowers perfect; 

upper elevation pastures Lolium perenne 

27b. Spikelets placed flatwise to rachis; both glumes present 28 

28a. Flowers staminate; wiry stoloniferous seashore plants Jouvea 

28b. Flowers perfect; caespitose alpine plants; Cerro Chirripo Grande 

Agropyron 

29a. Tall, stout, reedlike grasses, culms usually 2-12 m. tall; panicles large, plumelike, 
spikelets silky because of abundant long hairs attached to lemmas or rachillas 

(glabrous in staminate Gynerium) 30 

29b. Grasses of various statures, but usually less than 2 m. tall; inflorescences not 

silky-hairy 33 

30a. Culms solid; leaves all in fan-shaped cluster near top of culms; spikelets with 2 
florets, the staminate ones glabrous; panicles more than 1 m. long on larger 

plants Gynerium sagittatum 

30b. Culms hollow; leaves basal or along culms; spikelets with more than 2 

florets 31 

31a. Lemmas hairy 32 

31b. Lemmas glabrous; rachilla internodes long-hairy Phragmites australis 

32a. Leaf blade bases very broad, conspicuously clasping; leaves spaced evenly 
along culms; blades often yellow-striped; flowers perfect; cultivated for orna- 
ment, or escaped Arundo donax 

32b. Leaf blades narrow; leaves aggregated into basal cluster, the culms few- 
leaved; flowers functionally unisexual; usually paramo plants, one species 

rarely cultivated Cortaderia 

33a. One or both glumes much shorter than spikelet 42 

33b. Both glumes at least three-fourths as long as spikelet 34 

34a. Lower 1 or 2 florets much longer than terminal floret and either staminate or 

sterile 35 

34b. Lower florets about as long as upper florets, all perfect-flowered and similar 

to lowermost 37 

35a. Spikelets 3-flowered, 1 or both of lower florets with awns and either staminate or 

sterile; plants with sweet odor of coumarin 36 

35b. Spikelets 2-flowered, lower floret staminate, awnless; upper floret perfect, with 

conspicuous geniculate awn; plants not sweet-scented Arundinella 

36a. Glumes very unequal; both of the 2 lower florets sterile 

Anthoxanthum odoratum 



BURGER: FLORA COSTARICENSIS 15 

36b. Glumes equal; at least 1 of lower florets staminate HierochloU 

37a. Spikelets 2 cm. or more long; glumes many-nerved; annual crop, persisting after 

cultivation in mountain fields Avena saliva 

37b. Spikelets less than 2 cm. long; glumes 1-5-nerved 38 

38a. Lemmas with 3 conspicuous nerves; spikelets nearly sessile, arranged in 2 
rows along lower sides of the simple, elongated panicle branches; lemmas 

awnless or short-awned Leptochloa 

38b. Lemmas with 5 or more nerves; spikelets variously arranged, mostly in open 

panicles, not along lower sides of simple panicle branches 39 

39a. Florets 4-5; lemmas nearly awnless, bidentate at tip; rare introduction in high- 
elevation pastures Danthonia decumbens 

39b. Florets 2-3; lemmas awned, the awn from the back or between teeth; plants of 

upper elevations 40 

40a. Awn attached above middle of lemma Trisetum 

40b. Awn attached near base of lemma 41 

4 la. Rachilla extending above base of upper floret as a minute hairy bristle; perennial 

Deschampsia 
41b. Rachilla not extending beyond second floret; diminutive annual 

Aira caryophyllea 

42a. Lemmas with 3 conspicuous nerves 43 

42b. Lemmas with 5 or more inconspicuous nerves, or rarely only the midrib 

visible 50 

43a. Spikelets with single fertile floret, a differently shaped rudimentary floret above 

it 44 

43b. Spikelets with several-many similar florets 45 

44a. Inflorescence of 1-several whorls of spikes; second floret with evident 

lemma 60 

44b. Inflorescence a raceme of spikes; second floret much reduced, lemma scarcely 

wider than awn; rare, Boruca savannas Gymnopogon fastigiatus 

45a. Spikelets sessile, pectinately arranged in short, thick, 1-sided spikes borne in 1 or 2 

whorls 46 

45b. Spikelets borne on pedicels, either in panicles, or racemosely along slender 

branches attached to central rachis 47 

46a. Rachis of each spike extended beyond spikelets as naked tip; second glume 

bearing short, divergent awn Dactyloctenium aegyptium 

46b. Rachis covered with spikelets to its tip; glumes not bearing awns 

Eleusine indica 
47 a. Palea long-hairy on its upper half; tip of lemma split, the short awn arising between 

2 teeth; sandy Caribbean beaches Triplosis 

47b. Palea not long-hairy; tip of lemma various; plants not confined to sandy beaches . 48 

48a. Primary panicle branches elongated and simple, spikelets arranged in 2 rows 

along the lower side, on very short pedicels; lemmas awned or awnless . 49 

48b. Primary panicle branches at least in part with secondary branches; spikelets 

not arranged in rows along lower sides; some of pedicels at least half as long 

as spikelets; lemmas awnless Erogrostis 

49a. Glumes several-nerved; lemmas long-awned, spikelets 1-2 cm. long 

Gouinia virgata 



16 FIELDIANA: BOTANY 

49b. Glumes 1-nerved; lemmas short-awned or awnless; spikelets less than 5 mm. long 

Leptochloa 

50a. Spikelets all alike 51 

50b. Spikelets paired, one of each pair sterile, containing only empty lemmas, its 
rachilla not disarticulating; the other fertile, its lemmas 1-nerved, rachilla 
disarticulating; panicle dense, spikelike; introduced in upper elevation 

pastures Cynosurus cristatus 

51a. Leaf sheaths with united edges, at least for basal third of their length 52 

51b. Leaf sheaths with overlapping edges 54 

52a. Lemmas blunt-tipped, nerves running parallel to the midrib 

Glyceria plicata 

52b. Lemmas acute or awned, nerves converging toward the midrib 53 

53a. Spikelets 2 cm. or more long, all on evident pedicels Bromus 

53b. Spikelets less than 1 cm. long, subsessile, crowded in dense fascicles at tips of the 

few, rigid panicle branches Dactylis glomerata 

54a. Plants tall, stout, extensively stoloniferous; on coastal sand dunes; spikelets 

strongly compressed and keeled Uniola pittieri 

54b. Plants not stoloniferous; growing at middle and upper elevations; spikelets 
not strongly compressed and keeled 55 

55a. Lemmas nearly circular in outline, spreading at right angles to rachilla, awnless 

and without evident nerves Briza minor 

55b. Lemmas longer than wide, acute or awned at tip, placed at acute angles to 

rachilla 56 

56a. Lemmas awned or acuminate; callus never bearing cottony hairs; leaf blades 

with acuminate tips 57 

56b. Lemmas awnless, blunt or acute, pubescent on nerves or with a tuft of cot- 
tony hairs on callus; leaf blades with blunt, boat-shaped tips Poa 

57a. Anther 1, usually not exserted from the cleistogamous florets; small caespitose 

annuals, leaf blades usually 1-2 mm. wide Vulpia 

57b. Anthers 3, usually exserted during anthesis; leaf blades mostly 3 mm. or more 

wide; caespitose perennials, often tall Festuca 

58a. Low, delicate grasses with abundant tufts of capillary basal leaves; panicles 

open, delicate; spikelets 2 mm. or less long; anthers 3 . Agrostis bacillata 

58b. Coarse grasses, lacking capillary basal foliage; leaf blades elongated, often 

stiff and involute; panicles dense or spikelike; spikelets mostly more than 

4 mm. long; anthers 1, 2, or 3 Calamagrostis 

59a. Lemmas plainly 3-nerved, tapering to an acuminate apex; panicle dense, cylindri- 
cal, dark gray; rare; Chirripo Grande Muhlenbergia nigra 

59b. Lemmas faintly 5-nerved, awnless or with dorsal awn; panicles open or dense; 

plants widespread at upper elevations Agrostis 

60a. Culm internodes solid, pithy; spikelets arranged in 2 evident rows along 
rachis; fertile lemma greenish or tan, bearing an awn as long as or longer than 

body; plants widespread Chloris 

60b. Culm internodes hollow; spikelets 2-rowed but overlapping and forming a 
single file; fertile lemma chocolate brown, nearly awnless; plants of sandy 
Caribbean beaches Eustachys petraea 



BURGER: FLORA COSTARICENSIS 17 

KEYV 

SPIKELETS DISARTICULATING FROM THE PEDICELS INDIVIDUALLY, 
WITHOUT ATTACHED RACHIS OR BRISTLES 

la. Spikelets all alike in appearance, usually with perfect flowers 3 

Ib. Spikelets of 2 unlike kinds, frequently some abortive or unisexual 2 

2a. Inflorescence a single erect rame, bearing pairs of unlike spikelets; 1 of each 
pair long-awned, detachable, and perfect-flowered, the other awnless, persis- 
tent, and staminate; grasses of dry savannas Trachypogon 

2b. Inflorescence a panicle or raceme; spikelets awnless, all unisexual; plants of 

moist or marshy areas 43 

3a. Spikelets when mature covered with hooked spines 

Pseudoechinolaena polystachya 

3b. Spikelets not covered with hooked spines 4 

4a. Spikelets laterally compressed 5 

4b. Spikelets dorsally compressed or terete 17 

5a. Spikelets borne in single raceme or spike 6 

5b. Spikelets borne in panicle or cluster of spikes 8 

6a. First glume missing, second glume leathery, its lower margins united; floret 

1 Zoysia 

6b. First glume present; margins of glumes not united; sterile lemma present 

below fertile floret 7 

7a. Spike erect, slender; first glume about as long as spikelet . . Mesosetum pittieri 
7b. Spike strongly reflexed, short and thick; first glume twice as long as rest of 

spikelet, tuberculate-hispid Echinolaena gracilis 

8a. Spikelets sessile, in slender or dense spikes 9 

8b. Spikelets pedicellate, in open or dense panicles 10 

9a. Spikelets awned, in very slender spikes; delicate annual weed; Meseta Central 

Arthraxon qvartinianus 
9b. Spikelets awnless, densely imbricated in stiff, short spikes; wiry perennial; coral 

beaches north of Limdn Spartina spartinae 

lOa. Spikelets concealed by long pinkish or silvery hairs Rhynchelytrum repens 

lOb. Spikelets not concealed by hairs 11 

11 a. Spikelets with 2 bracts only (lemma and palea), glumes missing; lemma awnless 

Leersia 

lib. Spikelets with 4 or more bracts; lemmas awned or awnless 12 

12a. Leaf blades borne on pseudopetioles Zeugites 

12b. Leaf blades lacking pseudopetioles 13 

13a. Spikelets with numerous florets; tall, stout, stoloniferous grasses of sea beaches 

Uniola pittieri 

13b. Spikelets with 1-2 florets; not sea beach grasses 14 

14a. Glumes longer than florets 15 

14b. "Glumes" (actually sterile lemmas) much shorter than floret Oryza 

15a. Foliage densely velvety-hairy; florets 2 Holcus lanatus 

15b. Foliage not velvety; floret 1 16 

16a. Glumes and lemma awned; rachilla not prolonged . . . Polypogon elongatus 



18 FIELDIANA: BOTANY 

16b. Glumes and lemma awnless; rachilla prolonged behind palea 

Cinna poaeformis 

17a. Spikelets covered with long, dense, silky hairs 18 

17b. Spikelets glabrous or pubescent, but not silky-hairy 20 

18a. Inflorescence golden-brown Eriochrysis cayanensis 

18b. Inflorescence white or grayish 19 

19a. Both glumes longer than thin, delicate floret Imperata 

19b. First glume much shorter than stiff, dark-colored floret Digitaria insularis 

20a. Leaf blades broad, longitudinally pleated Setaria 

20b. Leaf blades never pleated 21 

21a. Each spikelet subtended by 1 or more stiff bristles (sterile branchlets); inflores- 
cence a panicle 22 

21b. Spikelets not subtended by sterile bristles, every branchlet ending in a spikelet; 

inflorescence a panicle or group of racemes 23 

22a. Each spikelet subtended by a single bristle; spikelets with a broad papery 

wing when mature Ixophorus unisetus 

22b. Each spikelet subtended by several-many bristles; spikelets never winged 

Setaria 

23a. Inflorescence a single 1-sided raceme on each peduncle 24 

23b. Inflorescence of several-many racemes, or a panicle 25 

24a. Spikelets in 2 or 4 longitudinal rows, their sterile lemmas facing outward; first 

glume present or absent Paspalum 

24b. Spikelets in single longitudinal row, paired so that sterile lemmas of each 2 
successive spikelets are facing each other; first glume present . . . Thrasya 

25a. Spikelets awnless, with hardened knob-like protrusion at base, formed of first 
glume and rachilla joint Eriochloa 

25b. Spikelets awned or awnless, without basal knob-like protrusion; first glume evident 

or missing 26 

26a. Spikelets awned or awn-tipped 27 

26b. Spikelets blunt or acute, never awned 30 

27a. Foliage densely covered with sticky hairs; plants aromatic . Melinis minutiflora 

27b. Foliage not sticky-hairy; plants not aromatic 28 

28a. Plants decumbent or stoloniferous; leaf blades short, lanceolate or elliptical 

Oplismenus 
28b. Plants not stoloniferous; leaf blades linear 29 

29a. Spikelets narrow, with pointed basal callus; both glumes long-awned 

Chaetium bromoides 

29b. Spikelets ovoid, blunt at base; glumes not long-awned Echinochloa 

30a. Spikelets with 2 fertile florets, nearly spherical Isachne 

30b. Spikelets with a perfect terminal floret, lower floret staminate or sterile . 31 

31a. Spikelets borne in panicles 36 

31b. Spikelets borne in 1-sided spikelike racemes, all on lower sides of flattened or 

triangular rachises 32 

32a. Backs of fertile lemma and second glume turned toward rachis 33 

32b. Backs of fertile lemma and second glume turned away from rachis 35 

33a. Fertile floret soft and flexible, edges of lemma thin, exposed Digitaria 



BURGER: FLORA COSTARICENSIS 19 

33b. Fertile floret rigid, edges of lemma inrolled and concealed 34 

34a. Fertile lemma smooth; spikelets plano-convex; first glume small or absent 

Paspalum 
34b. Fertile lemma transversely corrugated; spikelets with rounded edges; first 

glume well developed 44 

35a. First glume well developed; spikelet with 3 bracts below fertile floret; fertile 

lemma corrugated Brachiaria 

35b. First glume absent; spikelet with 2 bracts below fertile floret; fertile lemma smooth 

Axonopus 
36a. Spikelets with 2 bracts below fertile floret, first glume missing 

Leptocoryphium lanatum 

36b. Spikelets with 3 bracts below fertile floret, first glume present 37 

37a. Spikelets placed very obliquely on tip of pedicel, rotund, turning black when 
mature; second glume and florets with minute tufts of hairs at tip; some species 

with woody culms Lasiacis 

37b. Spikelets not obliquely placed on pedicel; florets lacking tufts of hairs at tip; culms 

not woody 38 

38a. Fertile lemma with small, fleshy blisters, which leave scar-like depressions in 

drying, along its edges at base Ichnanthus 

38b. Fertile lemma lacking blisters or scars along its edges 39 

39a. Panicles dense, cylindrical and spikelike 40 

39b. Panicles more or less open, not spikelike 41 

40a. Spikelets strongly inflated or bulging on second glume side; blades narrow; 

culms less than 1 m. tall Sacciolepis 

40b. Spikelets not inflated; blades very wide, with prominent cordate bases; culms 

usually 2-3 m. tall Hymenachne 

41a. Both glumes as long as the pointed spikelet Homolepis aturensis 

41b. First glume shorter than spikelet 42 

42a. Fertile lemma with a laterally flattened, beaklike tip . Acroceras zizanioides 

42b. Fertile lemma rounded to tip, without beak Panicum 

43a. Leaf blades linear, elongated, acuminate, lacking pseudopetioles; aquatic or marsh 

plants Luziola 

43b. Leaf blades narrowly triangular, blunt-tipped, less than 5 x longer than wide, 

borne on short pseudopetioles Olyra 

44a. Leaf blades ovate, 4-5 times longer than wide, base cordate; racemes divari- 
cate, few; rachis of each raceme terminating in a spikelet Urochloa 

44b. Leaf blades linear, many times longer than wide, not cordate; racemes ap- 
pressed to rachis, many; rachis of each raceme terminating in a flattened 
sterile tip Paspalidium 

KEY VI 

SPIKELETS ALL OR SOME FALLING IN CLUSTERS OF Two OR MORE, OR ATTACHED TO 
RACHIS INTERNODES, PEDICELS, OR BRISTLES (REDUCED BRANCHLETS OR ABORTIVE 

SPIKELETS) 

la. Inflorescences usually arising directly from soil on short, leafless peduncles, club 
shaped, disarticulating into individual internodes, each bearing 3 flattened bracts, 



20 FIELDIANA: BOTANY 

each with 2 minute staminate spikelets, and concealing within them a slender 
rachis and a solitary sessile pistillate spikelet; rain forests, Caribbean lowlands 

Pariana parvispica 
Ib. Inflorescences all borne on leafy culms, various but never as in la 2 

2a. Inflorescence a slender simple panicle, each branch reduced to single stiff 
unbranched bristle that falls from rachis at maturity, bearing a single appressed 
permanently attached spikelet near its base Paratheria 

2b. Inflorescence various, but never with simple deciduous branches, each bear- 
ing solitary spikelet 3 

3a. Inflorescence a dense cylindrical bristly panicle; each spikelet or spikelet group 
surrounded by ring of long stiff bristles (reduced branchlets), with which it falls 

from the persistent rachis Pennisetum 

3b. Spikelets not surrounded by elongated bristles; inflorescence a panicle or group of 

spikes, rames, or spikelet fascicles 4 

4a. Rachis of individual spike or rame disarticulating into individual internodes at 

maturity, each carrying spikelets with it 9 

4b. Rachis remaining intact, spikelet groups falling from it, or entire inflores- 
cence falling 5 

5a. Inflorescence a single cylindrical or flattened spike or rame, without visible 

branches 6 

5b. Inflorescence a raceme of spikelet fascicles or short 1-sided spikes 7 

6a. Rachis flattened, corky, spikelets acute, sunken into 1 side of the rachis; 
leaves subopposite in pairs; sheaths strongly keeled 

Stenotaphrum secundatum 
6b. Rachis thin, truncate spikelets closely overlapping and surrounding it; leaves 

alternate Eremochloa ophiuroides 

7a. Spikelets borne in short, 1-sided spikes of more than 3 spikelets Bouteloua 

7b. Spikelets borne in fascicles of 1-3, often with short attached bristles 8 

8a. Spikelets 1-2 in each cluster, accompanied by bristles (reduced or abortive 

spikelets) Pentarraphis annua 

8b. Spikelets 3 in each cluster, all pedicellate; sterile bristles absent 

Aegopogon cenchroides 

9a. Sessile spikelets laterally compressed, glumes keeled 10 

9b. All spikelets dorsally compressed or spherical, glumes not keeled 12 

lOa. Spikelets awnless, members of each pair equal; inflorescence a large ter- 
minal panicle of verticillate rames; plants up to 2 m. tall, in dense, hard 

clumps Vetiveria zizanioides 

lOb. Spikelets awned, the pedicellate one absent or different from the sessile one; 

inflorescence not a large panicle 11 

lla. Spikelets solitary, the lowermost ones sometimes accompanied with a minute 
pedicel; low, creeping plants with short, cordate leaf blades 

Arthraxon quartinianus 
lib. Spikelets paired, dimorphic, pedicellate ones enlarged and flattened; plants erect; 

leaf blades linear Diectomis 

12a. Inflorescence silky-hairy, abundant hairs exceeding and concealing spike- 
lets 13 

12b. Inflorescence not silky-hairy, spikelets easily visible 14 



BURGER: FLORA COSTARICENSIS 21 

13a. Inflorescence open, pyramidal; hairs white Saccharum officinarum 

13b. Inflorescence dense, cylindrical (like Typha); hairs golden-brown 

Eriochrysis cayanensis 
14a. Spikelets, or some of them, sunken into hollows of thickened cylindrical 

rachis 15 

14b. Spikelets never sunken into thin or partially thickened rachis internodes . 17 
15a. Spikelets all unisexual, lower part of each inflorescence made up of a series of bony 
cylindrical internodes, each containing single pistillate spikelet; upper portion flat- 
tened, bearing paired staminate spikelets Tripsacum 

15b. Sessile spikelet of each pair with a perfect flower; inflorescence not as in 14a . 16 
16a. Rachis internode united with edge of the pedicel; pedicellate spikelets sterile; 

foliage bristly-hispid, irritating to touch Rottboellia exaltata 

16b. Rachis internode not united with pedicel, pedicellate spikelet sometimes with 

a flower; foliage not bristly Coelorachis aurita 

17a. Rames 1 on each peduncle (but culms sometimes bearing several to many pedun- 
cles, interspersed with bracts) 18 

17b. Rames 2-many on each peduncle, forming an inflorescence 21 

18a. Low, creeping stoloniferous grass; spikelets equal, in pairs or trios, at each 

node of rachis Polytrias amaura 

18b. Plants not low and creeping; spikelets in pairs, the sessile one fertile, usually 

awned, the pedicellate spikelet much reduced and sterile 19 

19a. Sessile spikelets spherical, 1-2 mm. in diameter, hard, black, rough and ridged, 

awnless Hackelochloa granularis 

19b. Sessile spikelets ovate, acute, never spherical, awned or awnless 20 

20a. Sessile spikelets perfect-flowered, usually awned; pedicellate spikelets re- 
duced, sterile Schizachyrium 

20b. Sessile spikelets pistillate, awnless; pedicellate spikelets staminate, awnless, 

as large as sessile ones Hypogynium virgatum 

21a. One spikelet of each pair sessile 22 

2 1 b. Both spikelets of each pair pedicellate and usually alike: pedicels of unequal length 

Ischaemum 

22a. First glume strongly cross-wrinkled; lower floret staminate . . Ischaemum 
22b. First glume not cross-wrinkled; lower floret sterile, represented by an empty 

lemma 23 

23a. Rachis segment and pedicels with thick margins and a very thin, translucent center 

line; first glume of sessile spikelets 5-9-nerved 24 

23b. Rachis segments and pedicels not thin in center; first glumes of sessile spikelets 

usually 2-5-nerved 25 

24a. First glume of sessile spikelets with conspicuous circular pit in the center, 
rames sessile in fan-shaped cluster, spikelet-bearing to their bases 

Bothriochloa 
24b. First glume of sessile spikelets lacking a pit; rames borne individually on 

slender weak peduncles along central rachis Euclasta 

25a. Foliage strongly lemon-scented; plants very rarely blooming 

Cymbopogon citratus 
25b. Foliage not lemon-scented; annual bloomers 26 



22 FIELDIANA: BOTANY 

26a. Individual rames of numerous pairs of spikelets 28 

26b. Individual rames numerous, of 1-7 segments (spikelet pairs), borne on lateral 
branches of large terminal, bractless panicle 27 

27a. Pedicellate spikelets present but awnless Sorghum 

27b. Pedicellate spikelets absent, only hairy pedicels present Sorghastrum 

28a. All pairs of spikelets of each rame alike, each with a fertile sessile spikelet 

Andropogon 

28b. Lowermost 1 or 2 pairs of spikelets of each rame awnless, staminate or 
sterile, others with perfect-flowered, awned sessile spikelets and awnless 
or rudimentary pedicellate spikelets Hyparrhenia 



ACIACHNE Bentham 

REFERENCES: Agnes Chase, Aciachne, a cleistogamous grass of the 
high Andes, J. Wash. Acad. Sci. 14:364-366. 1924. J. Reeder & C. 
Reeder, Parodiella, a new genus of grasses from the high Andes, Bol. 
Soc. Argent. Bot. 12:268-283. 1968. 

Low, pungent cushion grasses of high altitudes. Inflorescence a short spike of 1-3 
spikelets, mostly hidden among the leaves. Glumes obtuse, equal, stiff, the first 3-5- 
nerved, the second 5-nerved; nerves evident; disarticulation above the glumes; floret 1; 
lemma faintly 3-nerved, indurate, smooth and shining, tapering into a short, stiff, awn- 
like tip; callus blunt; palea about as long as the body of the lemma; lodicules 3, dimorphic, 
the broader pair each 1-nerved; third lodicule solitary, spatulate, nerveless. 

One species, restricted to the paramos of high mountains, mostly in 
the Andes. The genus is closely related to Lorenzochloa, which occurs 
in similar habitats. (Pooideae: Stipeae.) 

Aciachne pulvinata Bentham, in Hook., Icon. PL 14:44, pi. 1362. 
1880. Figure 1. 

Perennial, forming low cushions, 1-3 cm. high; culms much-branched; internodes very 
short, concealed by the densely overlapping sheaths; sheaths thin, hyaline, 3-5-nerved, 
somewhat gaping; ligule stiff, erect, truncate, scabrid on the back, ca. 0.7 mm. long, 
decurrent onto the sheath margins; blades numerous, forming a pungent fan-shaped 
cluster near the culm apex, folded, 4-10 mm. long, terete, glabrous beneath, erect or 
slightly recurved, with a pungent tip; upper surface with abundant short, peg-like hairs; 
blade in cross-section with a thick, continuous sclerenchyma layer covering the entire 
external surface and the edges of the upper epidermis; vascular bundles 3; mesophyll 
somewhat radially arranged, densely packed; prophylla prominent, stiff, the keels ex- 
serted as 2 pungent teeth. Inflorescence scarcely exceeding the foliage, a short spike of 
1-3 spikelets. Glumes obtuse, stiff, evidently nerved; lemma stiff, faintly 3-nerved, 
smooth and shining, tapering to a short awnlike tip; palea nearly as long as the lemma; 
anthers 3; style branches 2, separate. Chromosome number 2n = 22 (Reeder & Reeder, 
1968). 

The only Central American collection of this species is the following: 
Prov. San Jose: Valle de los Conejos, Chirripo Massiv, 3,500 m., 16 




FIG. 1. Aciachne pulvinata. A, portion of a matted plant; B, spikelet; C, floret. 

23 



24 FIELDIANA: BOTANY 

March 1971. H. Kuhbier 0393 (BREM, CR, ISC). High mountains of 
southern Costa Rica; Venezuela, Peru, and Bolivia. 

The occurrence of Aciachne along with two other xeromorphic 
grasses of Andean distribution, Lorenzochloa erectifolia and Stipa 
hans-meyeri, on the high paramos of Chirripo Grande in Costa Rica, 
poses a difficult question as to the manner of migration of these and 
many other high-altitude paramo plants that occur in both Central 
America and the Andes. 

ACROCERAS Stapf in Prain 

Sprawling annuals and perennials, the culms rooting at the lower nodes; inflorescence 
a panicle. Spikelets large, apiculate, the glumes and sterile lemma with pronounced 
crest-like keels at their tips; first glume nearly as long as the spikelet, 3-5-nerved; second 
glume and sterile lemma equal, 5-nerved; sterile lemma with a well-developed palea; 
fertile lemma rigid, smooth, with a laterally flattened herbaceous green beak, a circular 
depressed area on the back above the base; margins of lemma thickened but not involute; 
palea flat, rigid, with a small flattened bidentate herbaceous beak at its tip; rachilla thick 
and indurate, with definite internodes between the glumes and between the second 
glume and the sterile lemma. 

Acroceras is a small genus of tropical grasses, widespread in Africa 
and Asia. Acroceras zizanioides appears to be the only species found in 
the Americas, where it may have been introduced. The genus is some- 
what similar to the endemic American Lasiacis, but the resemblances 
may be coincidental. (Panicoideae: Paniceae.) 

Acroceras zizanioides (H.B.K.) Dandy, J. Bot. 69:54. 1931. A. 
oryzoides Stapf in Prain, Fl. Trop. Africa 9:622. 1920. Panicum 
oryzoides Swartz, Prodr. Veg. Ind. Occ. 23. 1788, not P. oryzoides 
Ard., Animadv. Spec. Alt. 16, pi. 5. 1764. P. zizanioides H.B.K. , Nov. 
Gen. & Sp. 1:100. 1816. Figure 2. 

Duration indefinite; plants sprawling or scrambling, rooting at the lower nodes; culms 
up to 2 m. long, the tips ascending; branching freely at lower nodes; culms glabrous, 
smooth, thick-walled, hollow; nodes glabrous or papillose-hispid. Sheaths shorter than 
the internodes, glabrous or papillose-hispid, especially near the apex; exposed margin of 
sheath papillose-hispid; ligule 0.2-0.5 mm. long, membranaceous; blades cordate at the 
base above a short pseudopetiole, glabrous or nearly so, sometimes papillose-hispid on 
the basal lobes of the blade, collar, and midrib above the base. Inflorescence terminal on 
the main culm or on leafy branches; panicles open, with few rather simple ascending 
branches, 9-35 cm. long, 2-10 cm. wide, mostly 2-4 times longer than wide. Spikelets 
mostly paired, one short pedicellate and the other longer pedicellate, on angular 
pedicels, appressed along the main panicle branches; Spikelets dorsally compressed, 
elliptic-ovate, 5.5-6.6 mm. long, glabrous; first glume 4.0-5.4 mm. long, ovate, 3-5- 
nerved, clasping the second glume; second glume 5-6 mm. long, 5-nerved; lower (sterile) 
lemma 4.5-5.4 mm. long, 5-nerved; palea 3.5-4.0 mm. long; anthers purple, 2 mm. long; 




FIG. 2. Acroceras zizanioides. A, spikelet; B, fertile floret; C, panicle. 

25 



26 FIELDIANA: BOTANY 

fertile floret 4.5-5.0 mm. long, palea with 2 marginal triangular membranaceous flanges 
just above the base. Chromosome number from Costa Rican specimens, n = 18. 

Common on shaded riverbanks and forest margins, shaded road- 
sides; mostly below 100 m. but occasionally to 1,100 m.; Caribbean and 
Pacific slopes; June to December, possibly yearlong. Southern Mexico 
to northern Argentina; West Indies; Tropical Africa. 



AEGOPOGON Humboldt & Bonpland ex Willdenow 

REFERENCE: A. A. Beetle, The genus Aegopogon Humb. & Bonpl. , 
Univ. of Wyoming Publications XIII:17-23. 1948. 

Delicate sprawling or stoloniferous grasses; inflorescence a unilateral raceme of de- 
tachable triads of spikelets, the triads borne on short persistent branchlets, in 2 rows 
along 2 sides of a triquetrous rachis; triad deciduous as a group, with a short segment of 
the branch below as a hairy stipe; each triad with 1 short-pedicellate or subsessile fertile 
spikelet and 2 longer-pedicellate sterile or staminate ones; fertile spikelet 1-flowered; 
glumes equal, shorter than the floret, awned from a bifid apex; lemma 5-lobed, the 2 
marginal lobes nerveless, membranaceous, the 3 prominent nerves each extending into 
an awn, the 2 lateral awns much shorter than the central one; palea about as long as the 
lemma, the nerves extending into awns; rachilla not extended beyond the floret. 

Aegopogon is a small genus of American grasses, found in warm, dry 
regions from the southwestern United States to South America. It is 
most closely related to Pentarraphis and Bouteloua. (Chloridoideae: 
Chlorideae.) 

KEY TO SPECIES OF Aegopogon 

la. Glumes oblong, narrow, lateral lobes acute; ligules 1.5-4.5 mm. long 

Ae. cenchroides 

Ib. Glumes flabellate, lateral lobes broadly rounded; ligules 0.7-1.5 mm. long 

Ae. tenellus 

Aegopogon cenchroides Humb. & Bonpl. ex Willd., Sp. PL 899. 
1806. Figure 3. 

Duration indefinite; plants sprawling, the culms rooting at the nodes, forming large 
patches; erect portions of culms 3-30 cm. long; branching abundant from the trailing 
culms; prophylla pointed, ciliate on the keels, 7-15 mm. long; culms 0.2-0.3 mm. thick, 
hollow, glabrous; sheaths much shorter than the internodes, glabrous to puberulent; 
ligules 1.5-4.5 mm. long, membranaceous; blades 2-10 cm. long, 1-2 mm. wide, glabrous, 
scabrous, or puberulent; peduncle slender, exserted 3-10 cm.; inflorescences solitary, 
terminal on the erect culm branches, 2-9 cm. long; spikelet triads in 2 rows, but usually 
oriented in one direction; stalk of the spikelet triad ca. 0.2 mm. long, bearded; pedicel of 
fertile spikelet ca. 0.3 mm. long, those of the sterile pair 0.4-0.7 mm. long; sterile 
spikelets range from nearly as long as the fertile one to minute rudiments; fertile 
spikelet 3.7-5.5 mm. long, excluding the central awn; glumes subequal, 3-9 mm., nar- 
rowly oblong, the apex bifid, the lobes acute, the awn making up half or more of the total 




FIG. 3. Aegopogon cenchroides. A, inflorescence; B, triad of spikelets. 



27 



28 FIELDIANA: BOTANY 

length; lemma glabrous, membranaceous, lanceolate, the undivided portion 1.5-2.5 mm. 
long, the lateral awns 1.5-2.5 mm. long, the central awn 3.5-8.5 mm. long; palea 2.5-5.2 
mm. long, including keel awns up to 1 mm. long; anthers 3, 0.5-2.0 mm. long, yellow. 
Chromosome numbers, from Costa Rican material, n = 20, 40. Hexaploids with n = 30 
are also known. 

Road embankments and open slopes, mid elevations from 1,400- 
2,700 m., volcanoes of the Meseta Central; Cordillera de Talamanca. 
June to December. Mexico to Colombia and Venezuela. 

The spikelets are extremely variable in awning and in the degree of 
development of the two sterile lateral spikelets, which range from 
sterile rudiments to a few which are either staminate or pistillate. The 
extreme morphological variability of our material does not appear to 
be correlated with the ploidy level. This small genus obviously needs 
further study. 

Aegopogon tenellus (DC.) Trin., Gram. Unifl. 164. 1824. Lamarckia 
tenella DC., Cat. Hort. Monspel. 120. 1813. 

Duration indefinite; culms sprawling and rooting at the nodes, the erect flowering 
portions 10-30 cm. long; branching abundant from the decumbent portions; prophylla 
10-12 mm. long, ciliate on the keels; culms 0.5 mm. or less thick, hollow, glabrous; nodes 
dark colored, glabrous; sheaths shorter than the internodes, glabrous or sparingly hir- 
sute; ligule a lacerate membrane, 0.7-1.5 mm. long; blades 1-7 cm. long, 1-2 mm. wide, 
glabrous or puberulent; inflorescence a unilateral raceme of spikelet triads, 2-5 cm. long, 
linear; pedicels of spikelets 1.0-1.5 mm. long, bearded; spikelets laterally compressed, 
4.5-5.5 mm. long, excluding the central awn; glumes 4.0-4.5 mm. long, 1-nerved, flabel- 
late, with a broad cordate apex, the midrib occasionally bearded near the base; un- 
divided portion of lemma ca. 2.5 mm. long; lateral awns ca. 2.5 mm. long, the central one 
ca. 11 mm.; palea ca. 4.5 mm. long, including awns ca. 2 mm. long; anthers 3, 0.6 mm. 
long, tan. 

The above measurements are taken from well-developed spikelets. 
Many specimens show much reduced spikelets , often with reduced 
awns (var. abortivus (Fourn.) Beetle). This species is known from 
Costa Rica only by the following specimen: Prov. de San Jose, Vicinity 
of Santa Maria de Dota, alt. 1,500-1,800 m., Standley 41720. Southern 
Arizona to Costa Rica. 



AGROPYRON Gaertner 

Caespitose or rhizomatous perennial grasses; inflorescence a solitary terminal bal- 
anced spike, the spikelets solitary at each node of the thin rachis and laterally appressed 
to it. Glumes equal, several-many-nerved; florets several; disarticulation above the 
glumes and between the florets; lemmas 5-7-nerved, awnless or awned from the tip; 
palea nearly as long as the lemma. 



BURGER: FLORA COSTARICENSIS 29 

A large genus in temperate and cold regions of both Old and New 
Worlds, much rarer in the southern hemisphere. The genus is closely 
related to Elymus, Triticwn, Secale, Hordeum, etc. (Pooideae: 
Triticeae). Compare also Brachy podium, which has similar inflores- 
cence and spikelets, but the individual spikelets on short pedicels. 

Agropyron attenuatum (H.B.K.) Roem. & Schult., Syst. Veg. 
2:751. 1817. Triticum attenuatum H.B.K. , Nov. Gen. & Sp. 1:180. 
1816. Figure 4. 

Perennial, 1-2 m. tall; culms erect, unbranched, the bases decumbent or rhizomatous; 
internodes glabrous, 2-3 mm. thick, thin-walled; nodes dark, contracted; sheaths mostly 
overlapping, striate, slightly puberulent near the apex; ligule firm, membranaceous, 0.7 
mm. long, continuous with the membranaceous sheath margin; blades up to 20 cm. long, 
2-5 mm. wide, glabrous or puberulent above and below; uppermost blade reduced. Spike 
11-14 cm. long, 5 mm. wide, the spikelets longer than the internodes and overlapping; 
rachis internodes thin, flat, scabrid on the angles, 6-7 mm. long. Spikelets 15-17 mm. 
long, laterally compressed; glumes equal, lanceolate or narrowly ovate, acute, flat, 
overlapping on the abaxial side of the spikelet, 11 mm. long, 5-7-nerved; florets 3-5, the 
terminal one rudimentary; lemmas lanceolate, 9-13 mm. long, rounded on the back, 
scabrid; awn lacking or up to 1.5 mm. long; palea 9-10 mm. long, scabrid on the keels; 
rachilla segments thick, 2.5-2.8 mm. long, the scar of disarticulation very oblique; 
anthers 3, 2.5 mm. long, yellow; ovary with a large deltoid pubescent appendage. 

Rare, paramos near summit of Chirripo Grande. This is the only 
North American locality for this species, previously known only from 
the Andes of Ecuador, Peru, and Bolivia. November-April. 

This species can easily be confused with Brachypodium mexi- 
canum, which occurs in the same area. The Brachypodium has short 
pedicels, 1-3 mm. long, whereas the spikelets of Agropyron are sessile 
or nearly so. 

AGROSTIS Linnaeus 

Mostly perennial grasses of temperate climates; plants caespitose, rhizomatous, or 
stoloniferous. Inflorescence a terminal panicle; spikelets numerous, small, laterally com- 
pressed; glumes nearly equal or the first slightly longer than the second, both exceeding 
the single floret; disarticulation above the glumes; lemma thin, faintly 3-5-nerved, the tip 
blunt or narrow, sometimes minutely toothed; callus often minutely bearded; lemma 
occasionally bearing a straight or geniculate awn; palea in various species absent, min- 
ute, or well developed; rachilla in one of our species (A. bacillata) produced behind the 
palea as a minute bristle, otherwise absent; anthers 3. 

Agrostis is a large genus of temperate and cold climates, in the 
tropics confined to high altitudes. The spikelets are similar to those of 
Calamagrostis, which differs in the possession of abundant callus hairs 
and a prolonged, usually hairy rachilla. (Pooideae: Agrostideae.) 



B 



FIG. 4. Agropyron attenuatum. A, spike; B, spikelet; C, a single floret. 



BURGER: FLORA COSTARICENSIS 31 

KEY TO SPECIES OF Agrostis 

la. Rachilla extended beyond base of palea as a bristle; lemmas awned or awnless 

A. bacillata 

Ib. Rachilla not evident beyond base of the palea 2 

2a. Palea at least half as long as lemma 3 

2b. Palea absent or less than half as long as lemma 5 

3a. Ligule of innovations less than 1 mm. long, those of culm leaves up to 2 mm. 

A. tennis 

3b. Ligules mostly 3-8 mm. long 4 

4a. Erect, rhizomatous plants A. gigantea 

4b. Trailing, mat-forming stoloniferous plants A. stolonifera var. palustris 

5a. Panicles narrow or spikelike, 5-10 x longer than wide, usually less than 1 cm. wide; 

basal leaf blades capillary, less than 1 mm. wide 6 

5b. Panicles open or diffuse, branches spreading, at least during flowering 7 

6a. Panicles dense, the rachis mostly concealed; pedicels shorter than spikelets; 
palea absent; awn twisted and geniculate; Cordillera de Talamanca 

A. tolitcensis 

6b. Panicles narrow but loose, rachis partly exposed; pedicels once to twice as long 
as spikelets; palea ca. 1 mm. long; awn straight; around summit of Volcan Poas 

A. pittieri 

7a. Plants with abundant basal foliage, leaf blades narrow, flat or folded; palea absent; 

awn present or absent 8 

7b. Plants lacking conspicuous basal foliage; panicles very lax and much-branched; palea 

minute; awn minute or absent A. perennans 

8a. Spikelets ca. 2 mm. long; lemma 1.2-1.4 mm. long, awnless or with a minute awn 

just below apex A. turrialbae 

8b. Spikelets 2.9-3.7 mm. long; lemma 1.7-2. 2 mm. long; awn inserted below middle 
of back, twisted and geniculate, exserted A. subpatens 

Agrostis bacillata Hack., Oesterr. Bot. Z. 52:59. 1902. Figure 7. 

Delicate, densely tufted perennial, 10-30 (-50) cm. tall; foliage mostly basal; culms 
erect, unbranched, glabrous, ca. 0.2-0.3 mm. thick, with 1-2 shorter internodes above 
the base, the terminal internode (peduncle) the longest; nodes purple; sheaths nearly as 
long as the internodes; ligule a thin white membrane, 1.7-4.3 mm. long, tapering to an 
acute apex; leaf blades 2-15 cm. long, 0.2-0.3 mm. thick as folded, stiffish and erect, 
minutely scaberulous on the lower surface, tightly folded; upper surface with a few 
coarse ridges. Peduncle exserted 2-6 cm.; inflorescence solitary, terminal, an open cylin- 
drical delicate panicle, 4-11 cm. long, 3-5 cm. wide; branches delicate, mostly paired, thin 
and flexuous, bearing spikelets on their outer half; pedicels spreading, longer than the 
spikelets. Spikelets 1.8-2.0 mm. long, the glumes equal or the second slightly shorter 
than the first, spreading apart at the tips, 3-nerved, ovate 4.5:1 as folded, acute, usually 
purple, the keel slightly scabrid; lemma ovate-obovate 3:1 as folded, 5-nerved, the apex 
blunt; a thin awn sometimes present, 0.3-0.6 mm. long, inserted on the back of the 
lemma ca. one-third below its tip; palea 1.1-1.4 mm. long; anthers 3, purple, 0.8-1.0 mm. 
long; rachilla prolonged behind the palea as a slender naked bristle, 1.1-1.4 mm. long. 
Chromosome number n = 14 from a Costa Rican specimen. 



32 FIELDIANA: BOTANY 

PaYamos above 3,000 m. elev.; Asuncidn, Cerro de las Vueltas, Chir- 
rip<5 Grande, above Llano Grande on Irazii. Apparently blooming 
yearlong. Endemic to Costa Rica. The type, Pittier 10477, was col- 
lected on the Cerro de la Muerte. 

This species is unusual in the genus Agrostis by its possession of a 
rachilla internode extended beyond the floret. In this it resembles 
species of Calamagrostis, which differ in having unequal glumes and 
prominent callus hairs. 

Agrostis gigantea Roth, Tent. Fl. Germ. 1:31. 1788. Agrostis alba 
Auth., non L. 

Vigorous rhizomatous perennial; plants 40-120 cm. tall, erect or the culm bases de- 
cumbent in wet sites; culms unbranched or branched from the lower nodes, glabrous, 
hollow; nodes glabrous; sheaths glabrous; ligule a thin white membrane, usually 3-6 mm. 
long, lacerate at the tip. Peduncle slender, exserted; inflorescence a solitary terminal 
panicle, 8-25 cm. long, 3-15 cm. wide, ovoid-pyramidal, usually rather open; branches 
fascicled, of various lengths; spikelets clustered, the pedicels usually shorter than the 
spikelet. Spikelets 2-3 mm. long; first glume ovate, acute, 1-nerved, longer than the 
similar second glume; glumes scabrous on the keel; lemma ca. 2 mm. long, ovate, acute, 
faintly 3-5-nerved; callus minutely bearded, tip blunt, usually awnless; palea ca. half as 
long as the lemma, with 2 faint vascular bundles; anthers 3, yellow, 1.0-1.5 mm. long. 

Moist pastures and roadsides; volcanoes of the Meseta Central, 
above 2,000 m. Blooming yearlong. 

This species is a cool-climate pasture grass of European origin. Its 
occurrence in dairy pastures on the volcanoes suggests that it was 
introduced in pasture seed mixtures, along with other European 
species. Two similar species, A. stolonifera and A. tennis, occur in the 
same types of habitats. This species has consistently been called A. 
alba in American literature for many years. However, European au- 
thors universally reject that name. The panicles have a reddish or 
brownish tinge when well developed, hence the English common 
name, "redtop." 

Agrostis perennans (Walt.) Tuckerm., Amer. J. Sci. 45:44. 1843. 
Cornucopiae perennans Walt., Fl. Carol. 74. 1788. An extensive 
synonymy is given in Hitchcock, Man. Gr. U.S., ed. 2. 1950. Figure 5. 

Weak, somewhat decumbent caespitose perennial; culms up 100 cm. long, unbranched 
or branching only from the base; internodes glabrous, hollow, 0.7-1.0 mm. thick; sheaths 
glabrous, ridged, shorter than the elongated internodes; ligule a thin, lacerate mem- 
brane, decurrent on the sheath margins, 2-5 mm. long; leaf blades flat, 6-13 cm. long, 
1.5-3.0 mm. wide, ridged, scaberulous. Peduncle slender, exserted 8-15 cm.; inflores- 
cence a solitary terminal panicle, 11-15 cm. long, 6-11 cm. wide, open and delicate, 
ovoid-pyramidal; branches up to 7 per node, including some solitary elongated pedicels; 




B 



FIG. 5. Agrostis perennans. A, panicle; B, spikelets; C, floret. 



33 




FIG. 6. Agrostis species. A. turrialbae: A, panicle; A. tolucensis: B, plant, C, spikelet, 
D, floret; A pittieri: E, panicle, F, spikelet, G, floret. 



34 



BURGER: FLORA COSTARICENSIS 35 

branches delicate, flexuous, rebranching at or below the middle; pedicels all spreading, 
longer than the spikelets. First glume 2.2-2.9 mm. long, 1-nerved, ovate, caudate, the 
tip slightly keeled; midrib scabrous; second glume similar, shorter, 1.9-2.3 mm. long; 
lemma ovate, 1.7-1.8 mm. long, very faintly nerved; callus appearing glabrous except 
under high magnification, tip erose or bifid, occasionally with a minute awn from the bifid 
apex; palea minute, nerveless; anthers 3, purple, 0.8-1.0 mm. long. 

Forests and paramos, 2,900-3,300 m. elevation, Asuncion, La Geor- 
gina, and other scattered localities on the Cordillera de Talamanca. 
June to August. 

Our plants seem similar to the woodland phase of A. perennans from 
the United States; however, three of our specimens for which we have 
chromosome counts indicate a number of n = 14, whereas counts from 
temperate North America shown = 21. A single count from Mexico by 
Dr. Reeder also indicates n = 14. Agrostis laxissima Swallen from 
Guatemala appears very similar to our plants, but has a well-developed 
awn. Agrostis turrialbae, which is regarded as endemic to Costa Rica, 
is similar to A. perennans, differing in the possession of abundant 
basal foliage. Its chromosome number is not yet known. This complex 
of species needs detailed morphological and cytological study. 

Agrostis pittieri Hack., Oesterr. Bot. Z. 52:60. 1902. Figure 6. 

Perennial, 30-60 cm. tall, in dense tufts with numerous intravaginal innovations; culms 
erect, 0.5-1.0 mm. thick, the internodes glabrous; culm nodes purple; internodes 3, 2 
shorter internodes at the base of the culm, the peduncle longer; foliage mostly basal; 
sheaths glabrous or slightly scaberulous toward the apex; ligule a thin membrane, 
2.5-3.5 mm. long; basal blades 7-15 cm. long, 0.6-1.0 mm. wide, folded, minutely 
scaberulous on the lower surface, coarsely ridged above; culm blades usually shorter and 
not folded. Inflorescence a solitary terminal panicle, 9-11 cm. long, narrow but loose, 
0.5-1.0 cm. wide, relatively few-flowered; branches slender, erect, 2-many from each 
node; pedicels erect, scabrous, 1-2 x as long as the spikelet. Spikelets laterally com- 
pressed; glumes 1-nerved, purplish toward the tips, scabrous on the keels; first glume 
2.9-3.9 mm. long; second slightly shorter, 2.8-3.4 mm. long; lemma 1.9-2.0 mm. long, 
ovate, thin, faintly nerved, 4-toothed at the apex; callus minutely bearded; awn 2.0-3.0 
mm. long, straight, inserted at or just below the middle of the lemma; palea a minute 
nerveless scale, 0.7-1.1 mm. long; anthers 3, purple, 1.2-1.5 mm. long. Chromosome 
number n = 21 from a collection from Poas. 

This species is endemic around the crater of Volcan Poas, above 
2,500 m. It occurs in meadows, on road embankments, on cinders near 
the crater, and in openings of the cloud forest. Blooming yearlong. 

Agrostis stolonifera L., Sp. PL 62. 1753, var. palustris (Huds.) 
Farwell, Rep. Michigan Acad. Sci. 21:351. 1919. A. palustris Huds., 
Fl. Angl. 27. 1762. 



36 FIELDIANA: BOTANY 

Perennial; low, creeping, spreading extensively by slender, elongated stolons, form- 
ing a dense leafy mat; branching frequent; stems hollow, glabrous; sheaths glabrous; 
ligule a thin membrane, up to 8 mm. long; blades 6-20 cm. long, 3-7 mm. wide. Inflores- 
cence solitary, terminal on the trailing stems; panicle slender, contracted, 6-12 cm. long, 
1-2 cm. wide, the branches ascending, the rachis usually hidden by the densely clustered 
short-pedicellate spikelets. Spikelets 2-3 mm. long; first glume ovate, acute, scabrous on 
the keel; second glume similar but slightly shorter; lemma ca. 1.5 mm. long, ovate, 
acute, faintly nerved; palea ca. two-thirds as long, anthers 3, ca. 1 mm. long, yellow. 

This European grass has been collected in moist pastures of 
Hacienda Central de Volcan Turrialba, at 2,600 m. elevation. Like A. 
gigantea and A. tennis, which occur in similar habitats, it was proba- 
bly introduced from Europe in pasture seed mixtures. It produces a 
lush, soft turf and is much used in temperate climates for golf greens. 
This group of European species is difficult to interpret, the species 
being highly variable, with several chromosome numbers and some 
reported hybridity. The English common name is "creeping bent." 

Agrostis subpatens Hitchc., N. Amer. Fl. 17:527. 1937. Figure 7. 

Perennial, in dense tufts; plants 20-50 cm. tall; culms erect; internodes 0.5-1.0 mm. 
thick, hollow, thin-walled, glabrous; culm nodes 2, purple, glabrous; sheaths nearly as 
long as the internodes, glabrous; ligule a thin white membrane, 3-5 mm. long; foliage 
mostly basal, the basal blades numerous, erect, tightly folded, ca. 0.6 mm. wide, 
scaberulous beneath, 5-15 cm. long; culm blades wider, 1-2 mm. wide, flat, up to 15 cm. 
long. Peduncle exserted up to 5 cm.; inflorescence a solitary, terminal, narrowly ovoid, 
purple panicle, 8-9 cm. long, the length 2-4 x the width; branches clustered, up to 7 per 
node, spreading at least during anthesis, scabrous, bearing spikelets mostly near the 
outer ends; pedicels spreading, scabrous, 1-2 x as long as the purple spikelets. First 
glume 2.9-3.7 mm. long, acute, ovate 6:1 as folded, scabrous on the keel; second glume 
similar but slightly shorter, 2.5-3.5 mm. long; lemma 1.7-2.2 mm. long, ovate, 4-toothed 
at the apex; awn inserted below the middle, usually about one-fourth above the base, 
twisted below, geniculate, exserted near the tips of the glumes; palea absent; anthers 3, 
purple, 1.0-1.5 mm. long; caryopsis 1.3-1.4 mm. long, narrowly ovate, amber. 

Open paramos above 3,000 m. elevation; frequent at Asuncion and 
Buena Vista; Villa Mills; Irazii; Chirripo Grande. Endemic to Costa 
Rica, the type from Cerro de la Muerte, Pittier 10470. 

This species is very similar to A pittieri which occurs on Poas. It 
differs in its more open panicle, lack of a palea, and longer awns. 
Despite the close resemblance, the single chromosome counts for these 
species indicate that A. pittieri is hexaploid, with n = 21, whereas A. 
subpatens is tetraploid with n = 14. 

Agrostis tenuis Sibth., Fl. Oxon. 36. 1794. 

Perennial, 10-70 cm. tall; plants erect or decumbent in some forms, spreading by 
rhizomes or stolons; culms branching from the base, hollow, glabrous; sheaths glabrous; 
ligule a short membrane, 0.2-2.0 mm. long, usually less than 1 mm.; leaf blades flat, 




FIG. 7. Agrostis species. A. subpatens: A, panicle and basal foliage; B, leaf base and 
ligule; C, spikelet and floret; A. bacillata: D, spikelets; E, plant and floret. 



37 



38 FIELDIANA: BOTANY 

glabrous or scaberulous, up to 15 cm. long, 1-5 mm. wide. Peduncle exserted; inflores- 
cence a solitary terminal panicle, ovoid-pyramidal, up to 20 cm. long, open and delicate, 
the branches naked below; pedicels short. Spikelets 2.0-3.5 mm. long; glumes ovate, 
acute, the first slightly longer than the second; lemma two-thirds to three-fourths as long 
as the glumes, ovate, blunt, faintly 3-5-nerved, rarely with an awn; palea one-half or 
more as long as the lemma; anthers 3, 1.0-1.5 mm. long. 

Rare or overlooked, moist pastures on the south slopes of Volcan 
Turrialba and Volcan Irazu. This species was introduced from Europe, 
probably as a pasture grass and appears to persist in pastures over 
2,000 m. elevation. Certain strains are "bent grasses," forming dense 
turf by the spreading stolons. 

Agrostis tolucensis H.B.K., Nov. Gen. & Sp. 1:135. 1816. A. 
hoffmannii Mez, Repert. Sp. Nov. 18:3. 1922. Figure 6. 

Dwarf perennial; plants erect, in dense small tufts; culms slender, ca. 0.5 mm. thick, 
hollow, glabrous, 8-32 cm. tall; nodes 1-3, purple, the lower internodes shorter; sheaths 
about as long as the internodes, glabrous; ligule 2.8-4.5 mm. long, a thin white mem- 
brane, its margins decurrent onto the sheath; foliage mostly basal, the numerous basal 
blades 0.7-1.0 mm. wide, tightly folded, 5-10 cm. long, erect, scaberulous; culm blades 
wider, 1-2 mm. wide, flat, scaberulous on both surfaces, coarsely ridged above, 2-9 cm. 
long. Peduncle included or exserted up to 8 cm. Inflorescence a solitary spikelike termi- 
nal panicle, very narrow and dense, 3-10 cm. long, 3-8 mm. wide, the branches fascicled, 
erect, short, rarely to 2 cm. long, spikelet-bearing to the base; pedicels erect, mostly 
scabrous, from very short to about as long as the spikelet; inflorescence purple or 
lead-colored. First glume 2.3-3.6 mm. long, acute, 1-nerved, ovate 6:1 as folded, scab- 
rous on the keel, usually purple; second glume similar but slightly shorter, 2.1-3.2 mm. 
long; lemma 2.0-2.8 mm. long, ovate, the apex 4-toothed; awn twisted and geniculate, 
inserted on the lower third of the lemma, 2.0-2.8 mm. long; palea absent; callus minutely 
barbed; anthers 3, purple, ca. 1 mm. long. Chromosome number n = 14 from a specimen 
from Irazii. 

Paramos, 3,000-3,400 m.; Asuncion, Las Vueltas, Villa Mills, Irazu, 
Turrialba; probably blooming yearlong. Mexico to Chile. 

This species, A. pittieri, and A. subpatens are all very similar in 
spikelet structure and appear to be closely related. The group merits 
further study. 

Agrostis turrialbae Mez, Rep. Sp. Nov. 18:4. 1922. Figure 6. 

Perennial, 10-40 cm. tall; culms erect or the bases decumbent and rooting when grow- 
ing in very wet sites; culms unbranched or somewhat branched from the base, 0.5-1.0 
mm. thick, glabrous, hollow; nodes 1-2, purple, glabrous; foliage mostly from near the 
base, the terminal internodes much longer than the lower; sheaths glabrous; ligule a 
thin, white membrane, 1.5-3.5 mm. long; leaf blades thin, flat, 5-10 cm. long, 1-2 mm. 
wide, the margins scabrid, surfaces glabrous or minutely scaberulous. Inflorescence 
solitary, terminal; peduncle slender, exserted up to 10 cm.; inflorescence a very open, 
delicate, elliptical or narrowly pyramidal panicle, 4-12 cm. long, 2-6 cm. wide; branches 



BURGER: FLORA COSTARICENSIS 39 

fascicled, up to 6 per node, sometimes a few very elongated solitary pedicels with the 
branches; branches branching once or twice, mostly on the outer half; pedicels longer 
than the spikelets, diverging strongly from the branches; rachis, branches, and pedicels 
usually shiny, glabrous or slightly scabrous. Spikelets purplish; first glume ovate, acute, 
scabrous on the keel, 2.0-2.1 mm. long; second glume similar, 1.8-2.0 mm. long, both 
apparently 1-nerved; lemma ovate, 1.2-1.4 mm. long, rather blunt, sometimes with a 
minute abortive awn on the back just below the summit; callus minutely bearded; palea 
absent; anthers 3, purple, 0.7 mm. long; caryopsis narrowly elliptical, amber. Chromo- 
some number n = 14 from Pinette 1297 from the Cerro de la Muerte. 

Moist areas in paramos, mostly above 3,000 m. elevation; Turrialba, 
Irazu, Las Vueltas, Cerro de la Muerte. February to August. Endemic 
to Costa Rica. 

This species has been identified from material available to me and 
from the original description and a purported portion of the type in 
US. The latter specimen, collected by Pittier, unfortunately has lost all 
of its spikelets, but resembles our specimens in other features. The 
original description by Mez indicates that the spikelets have long 
paleas. None of our specimens possesses a palea, but Mez may have 
been in error in his original observations. 

AIRA Linnaeus 

Caespitose annual grasses; inflorescence a terminal panicle; spikelets small; laterally 
compressed; glumes equal, longer than the concealed florets, hyaline, 1-nerved, rounded 
on the back; florets 2; disarticulation above the glumes and beneath the second floret; 
lemmas rounded on the back, tapering to 2 acuminate teeth; awns geniculate, twisted 
below, inserted on the lower part of the backs of the lemmas; rachilla not extended 
beyond the palea of the second floret. 

Aira is a genus of the temperate zone of the Old World, represented 
in the western hemisphere only by introductions. The genus is related 
to Deschampsia and Trisetum. (Pooideae: Aveneae.) 

Aira caryophyllea L., Sp. PI. 66. 1753. Figure 8. 

Diminutive caespitose annual; culms 4-15 cm. long, erect or decumbent at the base, 
branching from the base only, 0.5 mm. thick, hollow, glabrous; nodes glabrous; blades 
usually 1-2 per culm, borne on the lower half of the culm, 1-2 cm. long, less than 1 mm. 
wide; ligules pointed, 2-4 mm. long, membranaceous, decurrent on the sheaths; blades 
mostly withered at flowering time. Peduncle glabrous, slender, elongated, 4-7 cm. long; 
panicle very open, pyramidal, about as wide as long, 2-3.5 cm. long, with few branches, 
the spikelets clustered near their tips; pedicels 1-several times as long as the spikelets. 
Spikelets 2.5-3.0 mm. long; glumes equal or the first slightly longer; florets equal; lem- 
mas lanceolate, brownish, roughened above, 2. 1-2.2 mm. long, the nerves obscure; callus 
minutely bearded; awns once-geniculate, 2.8-3.2 mm. long; the basal segments brown, 
twisted, the tip exserted from the glumes; anthers 3, 0.3-0.6 mm. long. Chromosome 
number n = 14 from Costa Rican specimens. 




FIG. 8. Aira caryophyllea. Plant, spikelet, and florets. 
40 



BURGER: FLORA COSTARICENSIS 41 

This delicate little annual grass has been collected from pastures 
and the devastated area on Irazu, and also on Turrialba, from 3,000- 
3,400 m. elevation. June to August. This species is native to Eurasia 
and Africa. It occurs as an introduction in eastern and western United 
States, but has not previously been recorded from Mexico or Central 
America. Probably introduced in seed mixtures. 

European authors differ widely in their treatment of this species. 
Some separate a diploid race (n = 7) as true A. caryophyllea and 
regard the tetraploids as a separate species. Bocher & Larsen include 
both forms as A. caryophyllea (in Kongel. Danske Vidensk.-Selsk. 
Biol. Skr. 10, 2:4. 1958). 



ANDROPOGON Linnaeus 

REFERENCES: S. T. Blake, Taxonomic and nomenclatural studies in 
the Gramineae, No. 1, Proc. Roy. Soc. Queensland 80:55-84. 1969. W. 
D. Clayton, Studies in the Gramineae XXXI. The awned genera of 
Andropogoneae, Kew Bull. 27:457-474. 1972. F. W. Gould, The grass 
genus Andropogon in the United States, Brittonia 19:70-76. 1967. 

Usually perennial and caespitose grasses; inflorescences often complex, but basically 
composed of units of 2-many rames borne on a bracted or bractless peduncle; rames 
composed of several to many internodes, these disarticulating at maturity; rachis inter- 
nodes and pedicels flattened, not thin in the center; each internode bears a sessile, 
well-developed, fertile, usually awned spikelet at its base; pedicel similar, bearing a 
reduced, abortive, or obsolete spikelet; internode, pedicel, and spikelet pair shed from 
the plant as a unit; terminal segment of the rame composed of a sessile spikelet accom- 
panied by two pedicels bearing reduced or abortive spikelets. Sessile spikelet s ovate, 
acute, usually with an exserted geniculate awn; first glume flat or concave between 2 
laterally winged submarginal keels, its inflexed edges covering the margins of a boat- 
shaped, 1-nerved, keeled second glume; glumes subequal, cartilaginous, completely 
covering and concealing the inner spikelet parts; lower (sterile) lemma hyaline, nerve- 
less, flattened, conforming to the outline of the first glume, lacking a flower or palea; 
upper (fertile) lemma hyaline, narrow, tapering into an exserted awn, rarely with apical 
teeth; awn, when present, usually geniculate and twisted just above the base; palea 
lacking; lodicules oblong, hyaline, vasculated; anthers 1 or 3; style branches 2, separate; 
caryopsis linear or narrowly ovoid. Pedicellate spikelets much reduced or abortive, 
mostly lacking flowers, sometimes entirely lacking. 

The genus Andropogon is variously construed by authors. There is 
little agreement as to the generic limits. The following genera included 
in this treatment may by some writers be included in Andropogon: 
Bothriochloa, Cymbopogon, Diectomis, Euclasta, Hyparrhenia, 
Hypogynium, and Schizachyrium. The genus is worldwide in warm 
temperate and tropical regions. (Panicoideae: Andropogoneae.) 



42 FIELDIANA: BOTANY 

KEY TO SPECIES OF Andropogon 

la. Spikelets all lacking awns; anthers 3 2 

Ib. Sessile spikelets with conspicuous, exserted awns; anther 1 4 

2a. One or several of pedicellate spikelets at tips of each rame enlarged, conspicu- 
ous, longer than sessile spikelets; inflorescence a large ovoid compound mass; 

plants 1-1.5 m. tall A. bicornis 

2b. Pedicellate spikelets all much reduced or rudimentary; inflorescences 1-several 

per culm, individually long-stalked; plants less than 1 m. tall 3 

3a. Leaf blades up to 5 mm. wide, rounded abruptly to a boat-shaped tip; rames 3-5 per 

peduncle A. selloanus 

3b. Leaf blades 1.5-2.5 mm. wide, tapering to an acuminate tip; rames 2-3 per peduncle 

A. leucostachyus 
4a. Inflorescence a dense corymbose mass of numerous crowded pedunculate pairs 

of rames near apex of culm A. glomeratus 

4b. Inflorescence slender and elongated, made up of small groups of axillary pedun- 
cles bearing paired rames and arising from sheath axils of upper half of culm 

A. virginicw 



Andropogon bicornis L., Sp. PL .1046. 1753. Figure 9. 

Coarse caespitose perennial, in large, dense clumps; culms erect, up to 2.5 m. tall, 
branching abundantly from the middle and upper nodes; internodes glabrous, up to 6 
mm. thick, hollow, thick-walled; nodes glabrous; basal leaf sheaths densely overlapping, 
keeled; upper sheaths shorter than the internodes, glabrous; ligule a short, stiff mem- 
brane, 1.0-1.2 mm. long, minutely ciliolate; leaf blades up to 50 cm. long, 2-6 mm. wide, 
mostly glabrous or with a few hairs on the upper surface behind the ligule and occasion- 
ally with scattered papillose-based hairs on the basal margins; edges and midrib promi- 
nently scabrous. Inflorescence a large feathery ovoid compound mass, made up of 
numerous repeatedly branching axillary branches which terminate in slender wiry 
peduncles bearing 1-3 slender bladeless sheaths and terminating in a digitate pair (rarely 
3) of rames. Rames divergent, 2.5-3.5 cm. long, the rachis and pedicels bearded with 
hairs up to 8 mm. long; spikelets paired, the pedicellate member of each pair rudimen- 
tary or absent, or in the terminal triad, much enlarged and differing from the sessile 
spikelets; rachis internodes 2.5-3.0 mm. long; pedicels 3.4-4.0 mm. long. Sessile spikelets 
3.0-3.5 mm. long, ovate, acute; first glume flattened, with 2 lateral keels, nerveless 
between the keels; margins inflexed, clasping the edges of a boat-shaped, 1-nerved 
second glume 2.3-2.7 mm. long; lower (sterile) lemma 2.0-2.4 mm. long, conforming in 
shape to the first glume, hyaline, nerveless, its upper margins ciliate; upper (fertile) 
lemma 1.6-2.2 mm. long, hyaline, nerveless; anthers 3, 0.5-0.7 mm. long, purple; cary- 
opsis cylindrical, brown, 1.6-2.0 mm. long. One pedicellate spikelet of the terminal triad 
and occasionally 1 to several of the lower ones enlarged, conspicuous, 3.7-4.1 mm. long, 
somewhat laterally compressed, first glume convex on the back, 5-nerved; second glume 
boat-shaped, 3-nerved, 3.5-3.7 mm. long; sterile lemma 3.0-3.5 mm. long; fertile lemma 
2.8-3.0 mm. long; flower lacking or staminate, the 3 anthers 0.5-1.0 mm. long. Chromo- 
some number n = 30 from Costa Rican specimens. 

This species is a common weedy inhabitant of open roadsides and 
savannas or brushy areas, on both Pacific and Caribbean slopes, from 
low elevations to 1,500 m. The plants are conspicuous because of their 




FIG. 9. Andropogon species. A. bicomis: A, portion of a rame showing enlarged 
terminal spikelet; B, plant base and compound inflorescence; A. glomeratus: C, portion 
of rame with awned spikelets. 



43 



44 FIELDIANA: BOTANY 

large, plumy inflorescences. Flowering mostly from July to October, 
but more or less intact inflorescences may be found at other times of 
the year. Southern Mexico to Bolivia and Argentina; West Indies. 
Common names: Cola de Venado, Cola de Coyote. 

Andropogon glomeratus (Walt.) B.S.P., Prelim. Cat. N.Y. 67. 
1888. Cinna glomerata Walt., Fl. Carol. 59. 1788. Andropogon mr- 
ginicus L., var. abbreviatus (Hack.) Fern. & Grisc., Rhodora 37:142. 
1935. Figure 9. 

Densely caespitose perennial; culms erect, 60-150 cm. tall, branching freely from the 
middle and upper nodes; internodes up to 6 mm. thick, solid, pithy, glabrous; nodes 
glabrous; basal sheaths strongly keeled, closely overlapping; much of the foliage basal; 
margins of the sheaths appressed-hirsute, the back usually glabrous; ligule a stiff ciliolate 
membrane, 0.8-1.5 mm. long; leaf blades up to 60 cm. long, 4-7 mm. wide, the tip acute, 
boat-shaped; midrib keeled beneath, scabrous; margins sometimes with a few long hairs 
near the base. Inflorescence a large ovoid feathery mass, the numerous upper branches 
repeatedly branching, terminating in bracted peduncles, each bearing a pair (rarely 3) of 
divergent rames, each 2-3 cm. long; rachis internodes and pedicels strongly ciliate with 
silky hairs 5-8 mm. long; internodes 2.0-3.2 mm. long, the pedicels 3.5-4.2 mm. long. 
Sessile spikelets 3.2-3.5 mm. long, ovate 6:1, acute; first glume flat, with 2 marginal 
ciliate scabrous keels, the edges inflexed over the margins of the second glume; second 
glume 3.0-3.2 mm. long, 1-nerved, boat-shaped, keeled; lower (sterile) lemma hyaline, 
2.3-2.7 mm. long, conforming to the shape of the first glume; upper (fertile) lemma 
hyaline, 1-nerved, 2.0-2.5 mm. long, narrow, tapering to an awn 10-15 mm. long; base of 
the awn weakly twisted and geniculate near the base; anther 1, 0.8-1.3 mm. long, 
brownish; lodicules 2, oblong, hyaline, vasculated; caryopsis linear, up to 1.8 mm. long, 
brown. Pedicellate spikelets abortive, linear, 1-2 mm. long. 

Open roadsides, marshes, pastures, occasional in the Meseta Cen- 
tral; San Vito; elevations from 1,100-1,800 m.; beach at Limon. July to 
November, rarely later. Southeastern and southern United States; 
Yucatan and Central America; West Indies. 

This species is superficially similar to A. bicomis, but the plants are 
smaller, and the spikelets are awned. It also differs from A. bicomis in 
stamen number, the latter having three anthers. 

Andropogon leucostachyus H.B.K., Nov. Gen. & Sp. 1:187. 1816. 

Caespitose perennial in dense tufts; plants 40-100 cm. tall, culms erect, branching on 
the upper half; internodes 0.7-2.0 mm. thick, solid, pithy, glabrous; nodes glabrous; 
foliage mostly basal; sheaths keeled, glabrous; ligule membranaceous, 0.7-1.7 mm. long; 
leaf blades up to 32 cm. long, 1.5-2.5 mm. wide, keeled beneath, tapering to an acumi- 
nate apex; upper surface with a few weak hairs above the ligule. Peduncles slender, 
wiry, several exserted from each of the upper 3 or more leaf sheaths, each bearing a 
bladeless sheath; each peduncle bears a terminal inflorescence of 2-3 slightly divergent 
silky rames, 2-4 cm. long, the tan to purplish spikelets mostly concealed by the white to 
beige hairs; rachis internodes flattened, 1.8-2.7 mm. long, the apex obliquely cup- 



BURGER: FLORA COSTARICENSIS 45 

shaped; hairs up to 9 mm. long, the longest ones near the summit; pedicels similar but 
thinner, 2.5-3.5 mm. long. Sessile spikelets 2.7-3.2 mm. long, ovate 5-6:1, acute; callus 
bearded with silky hairs 4-5 mm. long; first glume 2.6-3.2 mm. long, 2-keeled; its margi- 
nal flanges inflexed and clasping the margins of the second glume; second glume 2.3-2.7 
mm. long, boat-shaped, 1-nerved, the keel convex; lower (sterile) lemma hyaline, con- 
forming in shape to the first glume, 1.8-2.6 mm. long, its upper margins ciliate, tip 
tapering into a slender weak included awn; upper (fertile) lemma hyaline, keeled, 1.5-2.5 
mm. long, ciliate on the upper margins; palea absent or a short, nerveless scale; anthers 
0.6-0.7 mm. long, yellow; caryopsis 1.8-2.3 mm. long, fusiform, amber; pedicellate 
spikelet abortive, 1.1-1.5 mm. long. Chromosome number n = 10 from Costa Rican 
specimens. 

Dry savannas at elevations up to 740 m.; La Cruz, Nuestro Amo, 
Buenos Aires, Paso Real, Boruca, Cabagra, Canas Gordas. April to 
December. Southern Mexico to Argentina; West Indies. 

Andropogon selloanus (Hack.) Hack., Bull. Herb. Boissier II. 
4:266. 1904. Andropogon leucostachyus ssp. selloanus Hack, in DC., 
Monogr. Phan. 6:420. 1889. 

Perennial, caespitose in small, dense clumps; culms 40-110 cm. tall, branching from the 
middle and upper nodes, erect; internodes to 3.5 mm. thick, solid, pithy, glabrous; nodes 
glabrous, slightly shrunken; foliage mostly basal, the upper leaf blades more or less 
reduced; sheaths shorter than the internodes, strongly compressed and keeled, gla- 
brous; ligule a short-ciliate membrane, 0.5-1.0 mm. long; leaf blades up to 40 cm. long 
and 5 mm. wide, ciliate near the base with scattered elongated, weak, papillose-based 
hairs; blade tip concave, boat-shaped, blunt. Peduncles several from each of the upper 
2-3 sheaths, slender, bearing bladeless sheaths. Individual inflorescences of 3-5 rames 
borne subdigitately at the bearded apex of the peduncle; rames forming a fan-shaped 
group, ascending, 3-6 cm. long; rames very silky, whitish or beige; rachis internodes 
2.0-2.8 mm. long, flattened, the apex obliquely cup-shaped, the edges bearded, the hairs 
up to 10 mm. long, the longest ones near the summit of the internode; pedicels similar 
but thinner, 3.5-3.8 mm. long. Sessile spikelets 3.2-3.5 mm. long, bearded on the callus 
with hairs up to 6 mm. long; spikelet acute, ovate ca. 5:1, the glumes glabrous; first 
glume concave between the 2 marginal keels, slightly winged below the bifid tip, its 
marginal flanges clasping the edges of the second glume; second glume equal to the first, 
boat-shaped, 1-nerved, the keel convex; lower (sterile) lemma 2.0-2.5 mm. long, flat- 
tened, conforming to the shape of the first glume, hyaline, nerveless, empty; upper 
(fertile) lemma hyaline, keeled, conforming to the second glume, narrowly triangular, 
nerveless, 1.5-2.0 mm. long, tapering to an acuminate apex or a weak short awn, the 
upper margins ciliate; palea absent or a small nerveless ciliate scale; anthers ca. 0.6 mm. 
long, white; stigmas emerging laterally from the glumes; caryopsis linear, ca. 1.7 mm. 
long. Pedicellate spikelet rudimentary, 0.6-1.2 mm. long, inconspicuous. 

This species is apparently rare in Costa Rica. Our only specimen is 
the following: Guanacaste, 4 km. S of LaCruz along the CIA, 230 m., 
rocky roadside in open savanna, 27 June 1968, Pohl & Davidse 10590B. 
Southern Mexico, Guatemala, Belize, Honduras, Costa Rica, and 
Panama to Argentina; West Indies. 



46 FIELDIANA: BOTANY 

Andropogon virginicus L., Sp. PL 1046. 1753. 

Caespitose perennial in dense tufts; plants 50-100 cm. tall; culms erect, branching 
freely from the middle and upper nodes; internodes compressed, to 4 mm. thick, hollow 
but partially pithy, glabrous; basal sheaths closely overlapping, strongly keeled, hirsute 
on the margins; foliage mostly basal; ligule a ciliolate membrane, 0.5-0.7 mm. long; leaf 
blades up to 35 cm. long, the basal ones longest, 2-5 mm. wide, hirsute near the base and 
on lower margins, strongly keeled beneath; branches several from each of the middle and 
upper nodes, slender and wiry, erect or ascending, each bearing several peduncles that 
arise in the axils of bladeless spathes; peduncles very short, less than 1 cm. long, each 
bearing at its apex 2-4 digitate, diverging rames 2-3 cm. long; subtending spathes mostly 
as long as the rames; rachis internodes and pedicels ciliate with abundant silky hairs, 
these up to 8 mm. long; rachis internodes 1.5-3 mm. long; pedicels 3.1-5 mm. long. 
Sessile spikelets narrowly ovate 4-5:1, acute, 3.8-4.1 mm. long; first glume flattened, the 
2 lateral keels scabrous-ciliate near the apex, the margins inflexed and covering the 
edges of the second glume. Second glume 3.5-3.6 mm. long, boat-shaped, keeled, 1- 
nerved; lower (sterile) lemma hyaline, 3.0-3.5 mm. long, conforming in shape to the first 
glume; upper (fertile) lemma hyaline, narrow, 2.5-3.0 mm. long, ciliate; awn 11-17 mm. 
long, twisted near the base; anther 1, 0.8 mm. long, purple; caryopsis ovate 4-5:1, 1.9-2.4 
mm. long, brown. Pedicellate spikelets rudimentary or absent. 

This is a common, highly variable species in the eastern and mid- 
western United States, extending southward to Panama and the West 
Indies. It is rare in Costa Rica, being known only by the following 
specimen: San Jose, Guadalupe, Hitchcock 8483, 22-24 October 1911. 

Andropogon virginicus is a member of an intricate complex of 
species or subspecific populations that intergrade freely. The common 
member of this group in Central America is A. glomeratus, which 
differs in its much denser and more compact inflorescence. 

ANTHEPHORA Schreber 

REFERENCE: J. P. Reeder, The systematic position of the grass 
genus Anthephora, Trans. Amer. Microscop. Soc. 79:211-218. 1960. 

Caespitose annual grasses; inflorescence a cylindrical spike of fascicled spikelets; fasci- 
cles overlapping, attached singly at the nodes of a tortuous rachis and readily detachable 
from it; fascicle with a short, thick basal stipe which bears 4 thick, rigid, many-nerved 
ovate bracts, these enclosing 2-4 spikelets, 1 or 2 of them sterile or reduced to small 
rudiments; first glume absent, second glume acicular, awned, 1-nerved; sterile lemma, 
fertile lemma and its palea subequal, as long as the spikelet; sterile lemma 7-nerved; 
fertile lemma faintly 3-nerved; caryopsis plump, elliptical, with a large embryo. 

Some authors interpret the bracts of the fascicle as first glumes of 
the spikelets. (Panicoideae: Paniceae.) 

Anthephora hermaphrodita (L.) 0. Kuntze, Rev. Gen. PI. 2:759. 
1891. Tripsacum hermaphroditum L., Syst. Nat. ed. 10. 2:1261. 1759. 
Figure 10. 






FIG. 10. Anthephora hermaphrodite. A, inflorescence; B, detached fascicle; C, 
spikelet inside of external bract; D, caryopsis. 



47 



48 FIELDIANA: BOTANY 

Caespitose annual; culms erect or sometimes decumbent and rooting at the lower 
nodes, branching from the base; culms glabrous, hollow, the nodes not prominent; 
prophylla up to 17 mm. long; leaves numerous, the sheaths mostly overlapping; sheaths 
and blades papillose-hispid to nearly glabrous; ligule a brownish membrane, 1.5-2.5 mm. 
long; blades flat, 4-17 cm. long, 2-8 mm. wide; peduncle included or exserted up to 10 
cm.; inflorescence solitary, terminal, slender, cylindrical, 4-12 cm. long, 5-8 mm. in 
diameter, bearing up to 60 fascicles; fascicles 5-7 mm. long, the bracts ovate, acuminate, 
flat and somewhat recurved near the tips; fertile spikelets 3.5-4.5 mm. long, ovate, 
acute; first glume absent; second glume acicular, awn-tipped, 1.7-4.2 mm. long; sterile 
lemma 3.6-4.5 mm. long, 7-nerved, scabrid between the nerves; fertile lemma 3.7-4.0 
mm. long, glabrous, faintly 3-nerved, its thin margins overlapping the edges of the 
palea; caryopsis plump, elliptical, ca. 2 mm. long. Chromosome number n = 9 from Costa 
Rican material. 

Sea beaches and lowland pastures and disturbed areas, especially 
common along the Pacific Coast. June to December, probably year- 
long. Mexico to Peru and Brazil; Caribbean Islands. 



ANTHOXANTHUM Linnaeus 

Caespitose grasses; inflorescence a dense, spikelike terminal panicle; spikelets later- 
ally compressed; glumes unequal, the first 1-nerved, much shorter than the 3-nerved 
second, which exceeds the florets and envelopes them; disarticulation above the glumes; 
florets 3, falling as a group; lower 2 florets sterile, lacking paleas; lemmas 5-nerved, 
obtuse and bifid at the tip; first floret with a straight awn from the back above the 
middle; second floret with a longer twisted geniculate awn from near the base; third 
(fertile) floret awnless, blunt, the lemma 1-nerved, slightly bifid; palea 1-nerved, longer 
than the lemma; anthers 2; flower perfect. Plants with odor of coumarin. (Pooideae: 
Phalarideae.) 

Anthoxanthum odoratum L., Sp. PL 28. 1753. Figure 11. 

Slender perennial, forming small tufts; culms erect or spreading, 30-60 cm. long, ca. 1 
mm. thick, hollow, glabrous; nodes dark, somewhat contracted, glabrous; leaves few; 
sheaths shorter than the intemodes, glabrous or with weak retrorse hairs, ciliate at the 
throat; blades 5-20 cm. long, 2-7 mm. wide, glabrous or with scattered weak, soft hairs, 
conspicuously auriculate, the dewlap often purplish. Peduncle slender, smooth, 10-35 
cm. long; panicle solitary, terminal, dense, 4-8 cm. long, cylindrical, the rachis covered 
by the imbricated spikelets; branches very short, the spikelets subsessile; spikelets 
lanceolate in outline, 6.5-9 mm. long; glumes membranaceous, glabrous or with scattered 
weak hairs, the first ovate, acute, 3.5-4 mm. long, 1-nerved, the second ovate, acumi- 
nate, 3-nerved, 6.5-8.5 mm. long; sterile florets subequal, 2.5-3.2 mm. long, the lemmas 
oblong, dilated near the tip, brownish and appressed-hirsute on the lower parts, whitish, 
glabrous, translucent near the tip; fertile floret 2.0-2.5 mm. long, the lemma glabrous, 
broadly ovate; flower protogynous, the stigmas and anthers extruding apically; lodicules 
absent or not functioning; anthers pink or purplish, 4-5 mm. long. Chromosome number 
n = 10 from Costa Rican material. 

Common along roads and in moist pastures; upper elevations of 




FIG. 11. Anthoxanthum odoratum. A, plant and inflorescence; B, awned sterile floret; 
C, awnless fertile floret; D, spikelet. 



49 



50 FIELDIANA: BOTANY 

Poas, Barba, Irazu, Turrialba; blooming from June to November, pos- 
sibly yearlong. This Eurasian grass was introduced into North 
America to give a sweet odor to hay. It occurs from Greenland and 
British Columbia southward through the moister parts of the United 
States. In Costa Rica, its occurrence in dairy pastures suggests that it 
was introduced as a component of early seed importations. 

This species is generally regarded as an undesirable weed, since it 
contains the bitter toxic substance coumarin, which is also responsible 
for the sweet, vanilla-like odor. 

ARISTIDA Linnaeus 

REFERENCES: J. Th. Henrard, A critical revision of the genus Aris- 
tida, Meded. Rijks-Herb. 54:VIII + 747. 1926, 1927, 1928, 1933; A 
monograph of the genus Aristida, Meded. Rijks-Herb. 58:1-325 + 159 
plates + XII. 1929, 1932. A. S. Hitchcock, The North American 
species of Aristida, Contr. U.S. Natl. Herb. 22:7:517-586. 1924. 

Annual or perennial, nearly always caespitose grasses of low to moderate stature, 
often of xeromorphic aspect; culms unbranched or less commonly branched; internodes 
slender, solid or thick-walled; sheaths usually somewhat keeled; ligule a minute ciliolate 
rim; blades flat or usually folded or involute. Inflorescence a terminal panicle, open or 
congested. Spikelets 1-flowered, disarticulating above the glumes; glumes keeled, sub- 
equal or unequal, usually 1-nerved, at least the first scabrous on the keel, the apices 
often bifid and with a short straight awn-tip; floret about as long as the glumes, or the 
column exceeding them; lemma rigid, cylindrical, its margins overlapping; callus oblique, 
sharp-pointed, often prominent, bearded with ascending hairs; apex of the lemma often 
prolonged into a straight or twisted beak or column, this often scabrous; awns 3, or by 
abortion of the lateral ones, single; central awn usually longer than the lateral ones, 
sometimes bent or curved; lateral awns similar to the central one or much shorter in 
some species; all awns in our species upwardly scabrous; palea small, completely con- 
cealed by the lemma, or not evident; lodicules 2 or 3; anthers 3, or by abortion, 1; 
caryopsis linear-cylindric. 

Aristida ; s a large genus of grasses distributed in temperate and 
tropical climates throughout the world. They are most abundant in 
grassland, savanna, and desert climates. Most of the species are low in 
the plant successional stages, and become very abundant upon distur- 
bance or overgrazing of grasslands. They have little forage value, and 
are disliked because of their offensive florets. The combination of a 
sharp, bearded callus, rigid lemma, and upwardly scabrous awns en- 
ables the florets to penetrate clothing, fur, or hair, or to irritate eyes, 
nostrils, and mouth. Henrard indicates that the genus contains about 
320 species. In spikelet structure, the genus resembles Stipa, but is 
not regarded as being closely related. Species such as A. temipes and 



BURGER: FLORA COSTARICENSIS 51 

A. jorullensis, with reduced lateral awns, may be confused with 
species of Muhlenbergia. (Arundinoideae: Aristideae.) 

KEY TO SPECIES OF Aristida 

la. Central awn well-developed, lateral awns rudimentary (up to 3 mm. long), or 

absent 2 

Ib. All 3 awns well-developed, laterals at least half as long as central awn 3 

2a. Lateral awns present but short; plants lacking scattered long weak hairs; pani- 
cles large and very open, up to 50 cm. long; spikelets borne near the tips of 

branches A. ternipes 

2b. Lateral awns absent; foliage and inflorescences bearing elongate weak hairs; 

panicle slender, up to 20 cm. long A. jorullensis 

3a. Panicles open, elliptical or pyramidal, rachis plainly exposed throughout the 

length 4 

3b. Panicles narrow, usually congested, axis more or less concealed by the branches and 

spikelets 5 

4a. Lemmas less than 3 mm. long; delicate low annual, usually less than 35 cm. tall, 

lacking curled basal leaves A. capillacea 

4b. Lemmas 10-12 mm. long; perennial, up to 1 m. tall; basal leaf blades persistent, 

conspicuous, curly A. laxa 

5a. All 3 awns loosely contorted above the base into loose ascending spiral; basal leaf 

blades conspicuous, persistent, curly A. recurvata 

5b. Awns not spirally contorted, central awn sometimes strongly recurved; plants lack- 
ing curly basal foliage 6 

6a. Lemma 8-9 mm. long, the upper 2.0-2.5 mm. twisted, scabrous; first glume 

scabrous only on the keel; foliage bearing elongated weak hairs A. orizabensis 

6b. Lemma less than 5.5 mm. long, the upper portion straight, not twisted; first 

glume scabrous on the keel and surface; foliage lacking elongated weak hairs 

A. tincta 

Aristida capillacea Lam., Tabl. Encycl. 1:156. 1791. Figure 12. 

Delicate tufted annual, in small dense clumps; plants 5-37 cm. tall; culms very slender, 
ca. 0.5 mm. thick, the internodes angular, reddish-speckled, glabrous, solid, branching 
from the base and usually from a middle node; leaves ca. 4 per culm, 2 from the base and 
2 from 2 adjacent middle nodes that are separated by a very short internode; sheaths 
glabrous; ligule a minute ciliolate rim, ca. 0.2 mm. long; leaf blades 0.5-0.7 mm. wide, 
folded; lower surface glabrous; upper surface ridged, scabrous, bearing scattered 
elongate weak hairs that emerge between the folded edges of the blades. Peduncle 
elongated, making up, with the panicle, ca. two-thirds of the height of the plant; inflores- 
cences terminal, often a second axillary one borne from a middle node of the culm; 
panicle open, delicate, ovoid 3:1, 3-10 cm. long; branches usually paired, up to 3 cm. long, 
bearing spikelets on their outer half; rachis and branches angular, scabrous; pedicels 
slender, flexuous, longer than the spikelets. Spikelets V-shaped, the glumes spreading; 
glumes subulate, scabrous on the keel and with scattered scabrous hairs on the surfaces, 
often purplish; first glume 2.2-3.0 mm. long, 1-nerved, scabrous on the keel, tapering to 
an awn tip; second glume similar, 2.5-3.5 mm. long, faintly 3-nerved; lemma linear- 
cylindric, 1.8-2.2 mm. long, including the blunt, bearded callus, scabrous near the apex; 




FIG. 12. Aristida capillacea. A, plant with panicles; B, group of spikelets; C, single 
floret. 



52 



BURGER: FLORA COSTARICENSIS 53 

column twisted, 1.5-2.2 mm. long; awns 3, slightly contorted, the central one 4.5-7.5 mm. 
long, the lateral ones slightly shorter; palea not seen; anthers 3, purple, 0.3 mm. long; 
caryopsis linear-cylindric, 1.4 mm. long, amber, translucent. Chromosome number n = 
11 from a Costa Rican specimen. 

The delicate little plants of this species occur on dry, open sites, 
mostly at low elevations and never over 1,000 m. They are especially 
common on volcanic tuff savannas in Guanacaste and have also been 
collected in the General Valley at Boruca, Buenos Aires, and Paso 
Real; Hacienda Argentina; San Ramon. December to February. 
Southern Mexico to northern South America, Brazil and Bolivia. 

Aristida jorullensis Kunth, Rev. Gram. 1:62. 1829. Figure 13. 

Caespitose annual, in dense, small tufts; culms 10-60 cm. tall; branching abundant 
from 1-3 culm nodes; inter-nodes very slender, solid, glabrous; nodes glabrous; leaf 
sheaths glabrous; ligule a minute ciliate rim, 0.1-0.2 mm. long; leaf blades 4-20 cm. long, 
1.0-1.5 mm. wide, folded or involute; upper surface uniformly finely ridged, scaberulous, 
with scattered elongated flexuous hairs that gyrate when wetted. Inflorescences termi- 
nal on the main culm or on leafy branches; peduncle slender, weak, up to 15 cm. long; 
panicle slender, 6-20 cm. long; rachis exposed between the isolated solitary branches; 
branches 1-4 cm. long, bearing appressed spikelets to their bases; rachis, branches, and 
glumes bearing elongated weak flexuous hairs. Spikelets V-shaped, the glumes diverg- 
ing, subequal; first glume subulate, 1-3-nerved, scabrous on the keel, 4.5-9.0 (rarely 19) 
mm. long; second glume similar, 5.0-8.5 (rarely 13) mm. long; floret 4-7 cm. long, without 
clear distinction of lemma and awn; callus ca. 0.5 mm. long, bearded with hairs ca. 1 mm. 
long; lemma somewhat laterally compressed, scabrous above in lines, linear, tapering 
gradually into a flattened scabrous beak and flexuous awn; lateral awns absent; palea 
1.0-1.5 mm. long; anthers 3, 1.1-1.7 mm. long, purple. Chromosome numbern = 11 from 
a Costa Rican specimen. 

This species occurs on dry Curatella-Byrsonima savannas on vol- 
canic tuff in northern Guanacaste, from sea level to 200 m. elevation, 
and in Crescentia savannas. It has also been collected at Turricares 
and Rodeo de Pacaca. Blooming mostly from September to January, 
occasionally in June and July. Pacific Coastal regions, from Central 
Mexico to Panama. 

This species is somewhat anomalous in the genus Aristida because of 
its lack of lateral awns. The general structure of the spikelets, how- 
ever, indicates that it is closely related to A. temipes, in which the 
lateral awns are very short. 

Aristida laxa Cavanilles, Icon, et Descr. PI. 5:44. 1799. A. spadicea 
H.B.K., Nov. Gen. & Sp. PL 1:123. 1816. 

Caespitose perennial in small dense tufts; plants up to 1 m. tall; culms unbranched; 
internodes 1.0-1.5 mm. thick, glabrous, solid; nodes glabrous, not prominent; sheaths 




FIG. 13. Aristida species. A. temipes: A, panicle; B, single floret; A. jorullensis: C, 
spikelet and single floret; D, portion of a panicle. 



54 



BURGER: FLORA COSTARICENSIS 55 

glabrous, slightly keeled; ligule ca. 0.5 mm. long, a short ciliolate crown; leaf blades 
15-30 cm. long, up to 2.5 mm. wide, flat near the base, involute above; lower surface 
glabrous; upper surface ridged, scaberulous, with scattered weak thin hairs near the 
base and throat; basal blades becoming twisted with age. Peduncle elongated, slender; 
inflorescence an open, solitary, terminal, pyramidal panicle; rachis and branches angu- 
lar, scaberulous; branches ascending, straight, solitary but branched into 2 just above 
the base, up to 8 cm. long; spikelets borne on the outer half of the branch, appressed, 
short-pedicellate. Glumes subequal, the first 9.5-11.8 mm. long, subulate 6:1, scabrous 
on the keel and the surfaces; second glume similar but glabrous, 10-12 mm. long; lemma 
linear-cylindrical, 10-12 mm. long; callus short, 0.5 mm. long, bearded with hairs up to 
1.5 mm. long; body of lemma often mottled with dark coloration, glabrous below, scabr- 
ous above, passing into a scabrous, twisted beak or column, 5-9 mm. long; central awn 
strongly curved at the base, straight above, 24-30 mm. long, the lateral awns shorter, 
somewhat spreading; anthers 3, ca. 1.6 mm. long, dark. 

Known from Costa Rica only by the following specimen: Guanacaste, 
Liberia, hilly Curatella-Byrsonima savanna on volcanic tuff, 14 Jan- 
uary 1969, P. & D. 11653. Mexico to Ecuador. 

Aristida orizabensis Fourn., Mex. PL 2:78. 1881. A. pseudo- 
spadicea Hubb., in Proc. Amer. Acad. Arts 49:500. 1913. A. orizaben- 
sis, \ar.pseudospadicea (Hubb.) Henrard, Meded. Rijks-Herb. 54:473. 
1928. A. arizonica, sensu Hitchc., Contr. U.S. Natl. Herb. 22:7: 568. 
1924, non Vasey. 

Caespitose perennial in dense tufts; plants erect; culms unbranched or sparingly 
branched, 15-85 cm. tall, ca. 1 mm. thick, hollow, glabrous; sheaths usually longer than 
the internodes, glabrous; ligule a minute ciliolate rim, 0.2-0.3 mm. long; leaf blades 
usually 15-30 cm. long, 1.5-2.0 mm. wide, glabrous beneath, flat near the base and folded 
or involute above; upper surface with flat, thickened marginal bands of sclerenchyma, 
the central parts finely ridged, scaberulous; throat and basal parts of upper leaf surface 
with scattered elongated weak hairs that gyrate when wetted; leaf tip tapering to a 
long attenuate point. Inflorescence a solitary terminal panicle, 8-17 cm. long, ca. 2 cm. 
wide, narrow, interrupted, the solitary branches ascending, branched immediately 
above the base and spikelet-bearing to the base, angular and scabrous. Spikelets ap- 
pressed to the branches, V-shaped, the glumes spreading; first glume 6.5-8.0 mm. long, 
including the short awn tip, triangular 6:1, scabrous on the keel; second glume similar, 
slightly longer, 7.0-8.0 mm. long, not scabrous; lemma linear-cylindric, dark mottled, 
7.8-9.0 mm. long, including the bearded callus 0.5-1.0 mm. long and slightly twisted, 
scabrous column 2.0-2.5 mm. long; awns divergent, the central one longer than the 
lateral ones and more curved at the base, 10-25 mm. long, the lateral ones slightly 
shorter; anthers 3, purple or yellow, 1.7-1.9 mm. long. Chromosome numbern = 22 from 
a Costa Rican specimen. 

Dry savannas, northern Guanacaste, at elevations up to 400 m.; 
Boruca. Blooming June to December. Principal season of bloom ap- 
pears to be from June to August. Southern Mexico to Panama. 

The plants are quite variable. Early season collections are generally 
shorter, whereas those collected in the dry season are tall. 



56 FIELDIANA: BOTANY 

Aristida recurvata H.B.K., Nov. Gen. & Sp. 1:123. 1816. 

Tufted perennial, in dense clumps; culms usually 50-70 cm. tall, erect, unbranched; 
internodes ca. 1 mm. thick, hollow, glabrous; basal foliage abundant and persistent, the 
blades flat, 2-3 mm. wide, up to 30 cm. long, thick, with broad, flat marginal bands of 
sclerenchyma; middle of upper suface finely ridged and scaberulous, bearing scattered 
elongate weak hairs; blades becoming spirally curled; upper blades involute, ca. 1 mm. 
wide; sheaths longer than the internodes, glabrous; ligule a minute ciliolate rim, less 
than 0.2 mm. long. Peduncle slender, glabrous, 10-23 cm. long; inflorescence a solitary 
terminal panicle, 5-30 cm. long, narrowly cylindrical, less than 2 cm. wide, dense; 
branches numerous, ascending, overlapping, mostly 1-3 cm. long, many-flowered; 
spikelets crowded on the branches, their pedicels erect, 1-3 mm. long. Spikelets 8.5-12.5 
mm. long, excluding the awns, slender; first glume linear, tapering to a short awn, 
1-nerved, 8.5-12.5 mm. long, the keel scabrous; second glume similar but slightly 
shorter, 8.0-10.5 mm. long, 1-nerved, not scabrous; floret linear, the short callus 
bearded; lemma glabrous below but scabrous in lines on the upper portion, 3.5-4.0 mm. 
long, tapering into a scabrous, twisted beak ca. 2 mm. long; awns loosely spirally con- 
torted on the lower part, 12-16 mm. long, the central awn slightly longer than the 2 
lateral awns; anthers 3, 1.4 mm. long, orange, connivent around the style branches. 

Uncommon or overlooked; dry Curatella-Byrsonima savannas on 
volcanic tuff, 200 m. elevation; Hacienda Las Animas; Liberia. De- 
cember and January. Belize, Costa Rica, Panama, Venezuela to Brazil. 

Aristida ternipes Cavanilles, Icon, et Descr. PI. 5:46. 1799. Figure 
13. 

Perennial, caespitose in large tufts, 80-150 cm. tall, the culms ascending to erect, 
unbranched, 1.5-4.0 mm. thick, glabrous, solid; nodes not prominent, glabrous; sheaths 
mostly overlapping, glabrous; ligule a stiff ciliolate rim, ca. 0.2 mm. long; leaf blades flat 
near the base and involute above, passing into an elongated attenuate scabrous tip; 
length up to 50 cm.; width 3-5 mm.; upper surface with appressed hispid hairs near the 
base; surface marked with alternating wide flat white bands of sclerenchyma and sets of 
several very narrow green scaberulous ridges. Inflorescence a solitary terminal open 
panicle, making up, with the exserted peduncle, half or more of the total height of the 
plant; length up to 50 cm.; shape open pyramidal; branches solitary but branched im- 
mediately above the base, appearing binate or ternate; rachis angular and scabrous 
above; branches slender, wiry, scabrous, bearing short-pedicellate spikelets only on the 
outer half and appressed to the branchlets. Spikelets linear, the glumes subulate, not 
strongly diverging; first glume 6.5-11.5 mm. long, faintly 3-nerved, tapering to a short 
awn, scabrous on the keel; second glume similar, 8-12 mm. long; lemma subulate, cylin- 
drical, glabrous, 15-22.5 mm. long to the point of insertion of the awns; callus 0.5-1.0 
mm. long, bearded with hairs 2-3 mm. long; central awn stiff, arched, 10-15 mm. long; 
lateral awns erect, obsolete or up to 3 mm. long; palea stiff, up to 1.3 mm. long; anthers 
3, ca. 2.7 mm. long, tan; caryopsis linear-cylindric, 7.0-8.5 mm. long, amber. 

Dry savannas, northern Guanacaste, Nicoya Peninsula; Atenas; Rio 
Catarata; sea level to 600 m. elevation. Blooming principally from late 
October to December. Rare bloom may occur on old culms at the 



BURGER: FLORA COSTARICENSIS 57 

beginning of the rainy season. Southwestern United States to Colom- 
bia and Venezuela; Caribbean Islands. 

This species is not readily recognized as belonging to Aristida be- 
cause the minute lateral awns can be overlooked. Aristida jorullensis 
has similar spikelets, but is much smaller. 

Aristida tincta Trin. & Rupr., Gramina Agrostidea III. Mem. Acad. 
Imp. Sci. Saint-Petersbourg, Ser. 6, Sci. Math., (Seconde Pt. Sci. Nat. 
5:111. 1849.) A. breviglumis Mez, Repert. Sp. Nov. (Fedde) 17:152. 
1921. 

Perennial; densely caespitose in small hard tufts; plants erect, 25-85 cm. tall; culms 
unbranched, 0.5-1.3 mm. thick, hollow but thick-walled, glabrous; sheaths longer than 
the internodes, glabrous; ligule a minute rim, ca. 0.2 mm. long; auricles sometimes with 
a few slender hairs; leaf blades stiff, ascending, flat or folded, up to 25 cm. long and 2.5 
mm. wide, glabrous beneath, ridged and scaberulous above, the margins with thick 
bands of sclerenchyma. Inflorescences solitary, terminal; peduncle exserted up to 20 
cm.; panicle narrowly cylindrical, 10-18 cm. long, rather dense; branches solitary, erect, 
1-4 cm. long, densely flowered to their bases. Glumes subequal, the first scabrous on the 
keel and surface, 4.5-6.7 mm. long, subulate; second glume similar but glabrous, 4.5-5.8 
mm. long; lemma 4.2-5.3 mm. long, including the very short, nearly glabrous callus, 
linear-cylindric, without a twisted column, coarsely scabrous toward the apex; central 
awn recurved, ca. 15 mm. long, the lateral awns ascending, 8-11 mm. long; anthers 3, 
1.2 mm. long. 

Aristida tincta occurs on the savannas of Buenos Aires, elevation 
250 m. It was collected by Tonduz in 1891 and 1892. The latter (Tonduz 
4879) is the type number of A. breviglumis Mez. Collections made in 
1943 by Jorge Leon and in 1966 by Alfonso Jimenez are from the same 
area. Blooming in February and March. This species is primarily South 
American, ranging from Brazil and the Guyanas to Venezuela, 
Panama, and Costa Rica. 

The name of this species was published in November 1849, although 
the title page indicates that the work was exhibited in a meeting in 
June 1842. The title, usually misstated, is Gramina Agrostidea, III., 
Callus obconicus (Stipacea). 

ARTHRAXON Beauvois 

Delicate creeping annual; inflorescences numerous, borne on slender terminal and 
axillary peduncles, fan-shaped, each composed of 2-several slender digitate spikes; 
spikelets sessile, solitary at each node of a slender disarticulating rachis, falling accom- 
panied by the rachis internode, sometimes with a minute abortive pedicel also attached 
at the base of the spikelet; spikelets laterally compressed; glumes subequal, completely 
concealing the inner bracts of the spikelet; first glume 5-nerved, membranaceous, folded 



58 FIELDIANA: BOTANY 

asymmetrically, keeled; second glume 3-nerved, keeled; sterile lemma a minute nerve- 
less scale; fertile lemma narrow, thin and hyaline, bearing a twisted brown awn near 
its base, the awn exserted from the tip of the spikelet; palea lacking. (Panicoideae: 
Andropogoneae.) 

Arthraxon quartinianus (A. Rich.) Nash, N. Amer. Fl. 17:2:99. 
1912. Alectoridia quartiniana A. Rich., Tent. Fl. Abyss. 2:448. 1852. 
Figure 14. 

Culms sprawling, rooting at the lower nodes, 10-75 cm. long; branching profuse, the 
plants making spreading patches; prophylla brown, membranaceous, 10-20 mm. long; 
culms slender, hollow, glabrous; nodes bearded with spreading pubescence; sheaths 
much shorter than the internodes, ciliate along the margin, sometimes sparsely hirsute 
on the back; ligule a ciliate membrane, 1.0-1.5 mm. long; blades lanceolate, cordate- 
based, 2-6 cm. long, 3-11 mm. wide, ciliate on the margins, more or less papillose-hirsute 
on both surfaces; peduncles thin, flexuous, up to 10 cm. long; inflorescences 1.5-5 cm. 
long, fan-shaped, purplish, the rachis internodes silky-ciliate; spikelets sessile, oblong- 
lanceolate, 3.0-3.5 mm. long, usually purplish, scabrous on the nerves near the apex; 
awn geniculate, exserted 3-5 mm; anthers purple, 0.5-0.6 mm. long. Chromosome 
number n = 18 from Costa Rican material. 

Occasional along roads and in moist seepy open areas, mostly in or 
near the Meseta Central. In Costa Rica, this species appears to flower 
from October to December. In Honduras, however, we have collected 
it in June and July. Southern Mexico, Guatemala, Honduras, Central 
Costa Rica. Introduced from the Old World. 

ARTHROSTYLIDIUM Ruprecht 

REFERENCE: F. A. McClure, Genera of bamboos native to the New 
World, Smithsonian Contr. Bot. 9:15-21. 1973. 

Plants caespitose; culms and branches not thorny; culms cylindrical, hollow, erect or 
clambering and drooping; midculm nodes with a single branch bud, covered with a pair of 
flattened bracts; branch subtended by a bulge on the main culm below the branch 
attachment; branches few-numerous in a fan-shaped cluster from the midculm and upper 
nodes; one branch (the primary one) usually larger than the others; leaf blades lacking 
pronounced commissural veins. Inflorescences determinate racemes, lacking bracts. 
Spikelets sessile or nearly so; glumes 1 or 2, the third bract a sterile lemma; perfect- 
flowered florets several, the rachilla terminating in a sterile reduced floret; lemma and 
palea gaping; lodicules 3, one smaller than the other two; anthers 3; stigmas 2. (Bam- 
busoideae: Arthrostylideae.) 

KEY TO SPECIES OF Arthrostylidium 

la. Erect or pendent plants, culms up to 2 cm. thick and 10-15 m. long; sheaths and 
internodes strongly hispid with appressed hairs A. pubescens 

Ib. Plants sprawling or trailing; culms 3 mm. or less thick, up to 3 m. long; culms and 
sheaths not hispid , A. venezuelae 

Arthrostylidium pubescens Ruprecht, Bambuseae Monogr. Ex- 




FIG. 14. Arthraxon qiMrtinianns. A, portion of a spike, the spikelets accompanied by 
rudimentary pedicels; B, inflorescence. 



59 



60 FIELDIANA: BOTANY 

ponit 29. 1839. Arundinaria pubescens (Rupr.) Hack., Oesterr. Bot. 
Z. 53:69. 1903. Figure 15. 

Caespitose bamboos, the culms 10-50 per clump, 10-15 m. long, at first erect, later 
arching and leaning, the upper ends long trailing and forming curtains of foliage; inter- 
nodes cylindrical, hollow, up to 2 cm. in diameter, green, densely hispid-scabrous with 
appressed glassy papillose-based hairs, their lumens filled with blackish material; 
sheaths tight, appressed-hispid as the internodes; blades of midculm sheaths erect, as 
wide as the sheath apex, up to 23 cm. long, appressed-hispid. Hairs of culm internodes 
and sheaths irritating, readily penetrating human skin; ligules of culm sheaths ca. 2 mm. 
long, thick and stiff, erose, bearing stiff brown branching trichomes up to 5 mm. long on 
their outer surface. Foliage-bearing branches numerous, up to ca. 40 per node, one 
longer and thicker than the others; internodes and sheaths of branchlets mostly glab- 
rous, the sheath margins ciliolate; auricles densely fringed with stiff erect branching 
brown bristles up to 9 mm. long; pseudopetioles flattened, 2-3 mm. long; leaf blades 
ovate 7-10:1, acute or acuminate, drooping, slightly glaucous, glabrous except for a few 
fine hairs on the lower surface near the base; margins scabrous. 

Forested slopes at elevations below 1,200 m., rare. We have col- 
lected this species twice in Costa Rica, these collections apparently 
being the first North American records. Although both colonies were 
vegetative, the specimens are a good match for South American mate- 
rial so named by McClure in the U.S. National Herbarium. The colony 
along Hwy. 232 between Bajo de Pacuare and Grano de Oro occupies 
an extensive area on a south-facing hillside below the road. The culms 
clamber into trees and their upper portions form dense drooping cur- 
tains of foliage. Our collections are: Prov. Cartago, 7 km. by road E of 
Rio Pacuare, elevation 900 m., 6 June 1976, Pohl & Pinette 13183; 
Moravia de Chirripo, 1,100-1,200 m., 9 August 1968, Pohl & Dwoidse 
10875. 

Arthrostylidium venezuelae (Steud.) McClure, J. Wash. Acad. Sci. 
32:172. 1942. Chusquea venezuelae Steud., Syn. PI. Glum. 1:337. 1854. 
Arundinaria standleyi Hitchc., Proc. Biol. Soc. Wash. 40:79. 1927. 

Slender weak bamboo, the culms 1-3 mm. thick, the lower internodes solid, the upper 
hollow, glabrous or retrorsely appressed-pubescent, scaberulous toward the apex; 
branches few per node; nodes glabrous or sparsely retrorse-pubescent; sheaths mostly 
glabrous, ciliolate on the overlapping margin toward the apex; sheath auricles truncate, 
bearing numerous flexuous brown bristles, up to 9 mm. long; ligule a minute ciliolate rim 
ca. 0.2 mm. long; pseudopetioles flattened, puberulent above, 1.0-3.5 mm. long; leaf 
blades flat, dark green, ovate 5-8:1, acuminate, 5-14 cm. long, 10-15 mm. wide, glabrous 
above, bearing scattered weak hairs beneath. Inflorescence of short racemes borne on 
leafy branches, 5-8 cm. long; rachis strongly flexuous; internodes 1.0-1.5 cm. long; 
spikelets subsessile, diverging strongly from the rachis. Spikelets 1-2 cm. long, very 
narrow; florets 4-8; first glume 3-4 mm. long, 5-nerved; second glume 4-5 mm. long, 
7-nerved; lemmas appressed-pilose, 9-nerved, 6.0-7.5 mm. long, tapering to an obtuse, 
awnless apex; palea subequal, ciliolate on the keels near the tip; rachilla internodes at 
least three-fourths as long as the lemma, flat below, tapering to a strongly thickened 




FIG. 15. Arthrostylidium pubescens. A, culm sheath with erect blade; B, foliage- 
bearing branch; C, a floret; D, a branch with spikelets; E, foliage-bearing branches 
arising from a bulge above the node. 

61 



62 FIELDIANA: BOTANY 

cupulate apex, glabrous except for minute cilia at the apex; anthers 3, yellow, 3.2-3.5 
mm. long. 

This species was originally collected in Costa Rica from the vicinity 
of El Muneco. The only flowering specimens are the type of Arun- 
dinaria standleyi, Standley & Torres 51060 and another specimen 
from the same area, Standley & Torres 50897. One recent collection 
(Pohl & Damdse 11787) from this area is vegetative. It occurred in 
dense moist forests south of El Muneco. Our most recent collection 
(Pohl & Pinette 13303) occurred in wet forests 3.6 km. by road NE of 
the Tapanti Bridge. The species here occurred as a large colony, the 
plants vinelike and ascending into trees to ca. 8 m., forming dense 
curtains of foliage. The slender culms arose from dense, knotty 
crowns. Lower portions of the culms were solid, but upper internodes 
had a small lumen. 

ARUNDINELLA Raddi 

REFERENCES: H. J. Conert, Beitrdge zur Monographic der Arun- 
dinelleae, Bot. Jahrb. 77:226-354. 1957. C. E. Hubbard, The genera of 
the Tribe Arundinelleae, Bull. Misc. Inform. 317-322. 1936. 

Perennial, mostly caespitose grasses; inflorescence a terminal panicle; spikelets usu- 
ally paired, on pedicels of differing lengths; spikelets laterally compressed, 2-flowered, 
usually V-shaped and wide open; glumes unequal, narrow, acute or acuminate, the first 
3-nerved, slightly shorter than the first floret, the second 3-5-nerved, much longer than 
the florets; disarticulation at the base of the second floret; lower floret sterile or stami- 
nate, its lemma acute, awnless, membranaceous, 3- or weakly 5-nerved; second floret 
much shorter than the first, perfect-flowered, its lemma acuminate, long-awned from the 
tip or between 2 minute teeth, weakly nerved, the margins inrolled over the margins of 
the palea, the callus bearded, awn geniculate, exserted; rachilla not prolonged beyond 
the floret. (Panicoideae: Arundinelleae.) 

KEY TO SPECIES OF Arundinella 

la. Awn 4-6 mm. long, the lower segment tightly twisted A. confinis 

Ib. Awn 8-13 mm. long, the lower segment straight or only loosely twisted 2 

2a. Leaf blades 3-6 mm. wide; culms 1.5-2.0 mm. thick, usually less than 1 m. long 

A. berteroniana 

2b. Leaf blades 8-25 mm. wide; culms 3-7 mm. thick, 1-4 m. long . . A. deppeana 

Arundinella berteroniana (Schult.) Hitchc. & Chase, Contr. U.S. 
Natl. Herb. 18:290. 1917. Trichochloa berteroniana Schult., Mant. 
2:209. 1824. 

Perennial, in small, dense clumps, tightly clinging to rocks or timbers; culms 75-115 
cm. long, erect to arching, rarely becoming decumbent and rooting from the lower 
nodes, usually unbranched, 1.5-2 mm. thick, hollow, glabrous; nodes appressed-pubes- 
cent; sheaths mostly overlapping, more or less appressed papillose-hispid; ligule 0.5 mm. 
long, a thickish membrane; blades up to 25-35 cm. long, 3-6 mm. wide, flat, more or less 



BURGER: FLORA COSTARICENSIS 63 

papillose-hispid above and beneath; auricular hairs prominent; midrib prominent; mar- 
gins with a thick stramineous band, scabrous. Panicle solitary, terminal, slender, 20-40 
cm. long, 4-6 x longer than wide; branches slender, virgate, mostly simple, 10-15 cm. 
long. Spikelets mostly paired, V-shaped, the glumes recurved, conspicuously nerved; 
first glume lanceolate 3.2-4.5 mm. long, 3-nerved, the nerves scabrous; second glume 
lanceolate, tapering to a narrow but often truncate apex, smooth, 4.2-5.5 mm. long; 
lower floret sterile, the lemma lanceolate, acute, usually 3-nerved or rarely weakly 4- or 
5-nerved near the apex, glabrous, palea 1.5-2 mm. long; upper floret disarticulating 
above the first floret, perfect-flowered; lemma 1.5-1.8 mm. long, narrowly lanceolate, 
faintly 3-nerved, scabrid, brownish when mature, the margins inrolled over the edges of 
the palea; palea 1.3-1.5 mm. long; awn once geniculate, the lower segment not strongly 
twisted; anthers 3, purple, 0.6-0.7 mm. long. Chromosome number n = 10 from Costa 
Rican material. 

Conert states that this species is rhizomatous. While rooting culms 
are found, these were usually knocked down by flowing water, and are 
not true rhizomes. The plants occur along streams, usually anchoring 
very tightly on rocks or dead logs. This species occurs occasionally 
along rocky streams on both the Caribbean and Pacific slopes, at eleva- 
tions from 60-1,400 m. Blooming is apparently yearlong. Mexico to 
Brazil; West Indies. 

Arundinella confinis (Schult.) Hitchc. & Chase, Contr. U.S. Natl. 
Herb. 18:290. 1917. Piptatherum confine Schult., Mant. 2:184. 1824. 
Figure 16. 

Stout caespitose perennial; culms 95-185 cm. tall, erect, unbranched; culm 4-5 mm. 
thick, hollow, glabrous; nodes appressed pubescent; leaf sheaths mostly overlapping, 
glabrous near the base, hispid near the apex; ligule a minute thickish membrane, 0.2-0.3 
mm. long; leaf blades 20-25 cm. long, 9-16 mm. wide, more or less papillose-hispid above, 
especially just above the ligule, or on both sides. Peduncle hollow, glabrous, 2-4 mm. 
thick, exserted 20-45 cm.; panicle solitary, terminal, cylindrical, dense, about 25 cm. 
long, 4-6 x longer than wide; branches densely whorled; floriferous to the base. 
Spikelets usually paired, rather densely arranged on the branches, laterally compressed, 
3.7-4.2 mm. long; first glume 2.2-2.9 mm. long, lanceolate, 3-nerved, the nerves ridged, 
scabrous; second glume 3.7-4.2 mm. long, 3-5-nerved, lanceolate, tapering to a slender 
truncate apex; lower floret sterile, its lemma 2.1-1.5 mm. long, glabrous, narrowly 
ovate, acute, 3-nerved, the nerves faint, palea 1.8-2. mm. long; fertile floret lanceolate, 
1.5-2. mm. long, bearded on the callus; awn 4-6 mm. long, geniculate, the lower segment 
brown, tightly twisted when mature; palea 1.3-1.6 mm. long; anthers 3, 0.8-0.9 mm. 
long, purple. 

Rare; savannas near El Paraiso, Boruca, and Canas Gordas at eleva- 
tions from 400-1,200 m. November to December. Mexico to Panama; 
West Indies. 

Arundinella deppeana Nees, Bonplandia 3:84. 1855. Figure 16. 

Perennial from knotty crowns, with many basal innovations; culms 1-4 m. tall, erect to 
arching or scrambling through brush, unbranched, 3-7 mm. thick, hollow, thick-walled, 




FIG. 16. Arundinella species. A. deppeana: A, panicle; B, spikelets and fertile floret; 
A. confinis: C, spikelets; D, fertile florets. 



64 



BURGER: FLORA COSTARICENSIS 65 

glabrous; nodes appressed-pubescent; sheaths overlapping, ciliate on the margin, 
appressed-papillose hispid, especially near the apex; ligule a minute ciliate membrane, 
0.2-0.3 mm. long; larger blades 25-50 cm. long, 8-25 mm. wide, more or less appressed- 
hispid on both sides, strongly so on the upper surface just above the ligule. Peduncle 
glabrous, 4-30 cm. long; panicle solitary, terminal, loosely cylindrical, 20-60 cm. long. 
4-5 x longer than wide. Spikelets usually paired and unequally pedicellate, often 
purplish, laterally compressed, 3.8-4.8 mm. long; first glume 2.8-3.2 mm. long, 3-nerved, 
lance-attenuate; second glume 3.8-4.8 mm. long, 5-nerved, lance-attenuate; lower floret 
2.3-2.5 mm. long, sterile; lemma lanceolate, acute, 3-nerved, glabrous, acute; the palea 
1.5 mm. long; second floret disarticulating above the first floret, perfect-flowered; lemma 
ca. 1.5 mm. long, lanceolate, faintly 3-nerved, bearded at the base; tapering to a min- 
utely bifid apex; awn flat, only slightly twisted, geniculate, 10-13 mm. long; palea 1-1.3 
mm. long; anthers 3, 0.7-1 mm. long, purple; mature fertile lemma scabrid, brownish, its 
margins inrolled over the edges of the palea. Chromosome number n = 10 from Costa 
Rican plants. 

Occasional, savannas, forest margins, brush, road embankments; 
Pacific slope, 300-1,700 m. elevation, from northern Guanacaste to 
Panama. Blooming yearlong. Mexico to Brazil; West Indies. 

Common name: Cola de venado. The panicles are sometimes sold for 
ornament. 

ARUNDO Linnaeus 

Giant perennial reeds, the culms arising from thick scaly rhizomes and forming large 
colonies; inflorescence a large plumy terminal panicle. Spikelets laterally compressed, 
plumose, V-shaped; glumes about equal, 3-5-nerved, nearly as long as the entire 
spikelet; florets 4-5, their tips all about at the same level; rachilla disarticulating above 
the glumes and between the florets; lemmas with 3 principal vascular bundles and 2-4 
weak secondary ones, densely long-hairy on the lower portions of the back, minutely 
awned between 2 hyaline teeth; tip of the glabrous rachilla bearing a reduced abortive 
floret. 

Species three, in Formosa, Asia, and the Mediterranean lands; one 
species naturalized in warm temperate and tropical parts of the 
Americas. The genus is related to Cortaderia and Gynerium, and, like 
them, has plumy spikelets. (Arundinoideae: Arundineae.) 

Arundo donax L., Sp. PL 81. 1753. Figure 17. 

Culms arising from thick, scaly rhizomes; plants up to 8 m. tall, culms erect or arching, 
simple or extravaginally branched above; nodes glabrous, mostly concealed; internodes 
hollow, up to 4 cm. thick; foliage distributed rather uniformly along the culm except in 
old stems, strongly distichous; sheaths longer than the internodes and strongly overlap- 
ping, glabrous; leaf blades up to 1 m. or more long, up to 6 cm. wide, glabrous, the 
margins scabrous; leaf bases broader than the sheaths, with prominent triangular 
brownish flanges ciliate on the margins; ligule a thin whitish or brownish minutely ciliate 
membrane, 1.0-1.5 mm. long. Inflorescence borne on a cylindrical glabrous hollow 
peduncle up to 1.5 cm. thick; panicle up to 60 cm. long, ovoid, dense, the branches 




FIG. 17. Arundo donax. A, culm internode and leaf; B, branch of panicle with 
spikelets; C, single spikelet; D, one floret. 



66 



BURGER: FLORA COSTARICENSIS 67 

ascending. Spikelets densely clustered along secondary or tertiary branches, 10-14 mm. 
long; glumes hyaline, brownish or purplish, 11-13 mm. long, acuminate; florets 4-5, the 
upper ones progressively shorter than the lower, so that the tips are about at the same 
level; lemmas 8-12 mm. long, lance-ovate, tapering into a short straight awn which arises 
between 2 delicate lateral teeth; nerves 3-7, usually 3 major ones anastomosing with the 
midrib; lower portions of the back of the lemma heavily bearded with long, silky whitish 
hairs, up to 8 mm. long; palea up to 5 mm. long, about half as long as its lemma, whitish, 
membranaceous, scabrid on the keels and pubescent near the base between them, hya- 
line, truncate; callus short, rounded, short-hairy at its upper end; rachilla glabrous; 
flower with 2 truncate lodicules; stamens 3, the anthers 2.5-3.0 mm. long, yellow; pistil 
with 2 apical elongated style branches, terminating in plumose cylindrical brownish 
stigmas. 

Cultivated in the Meseta Central for ornament, and escaping to 
roadsides and river banks; practically never blooming under Costa 
Rican conditions. 

Most of the cultivated plants of this species in Costa Rica are the 
form with leaves longitudinally yellow-striped. This has been called 
var. versicolor (Mill.) Stokes. Our only flowering specimens of this 
species are of the striped form, and were growing in San Jose. It seems 
probable that the plants will bloom under Costa Rican conditions only 
where supplied with artificial illumination to extend the day length. 
Some escaped stands are of the wild type with green leaf blades. 
Common name: carrizo. 

AULONEMIA Goudot 

REFERENCE: F. A. McClure, Genera of bamboos native to the New 
World, Smithsonian Contr. Bot. 9. Aulonemia, pp. 53-61. 1973. 

Caespitose bamboos of small stature, forming small clumps; culms succulent, arising 
from scaly short, thick (pachymorph) rhizomes; culms leafy above the middle, erect or 
scrambling in vegetation; midculm branches mostly solitary and about as large as the 
main culm and strongly divergent from it, the subtending leaf sheath gaping; sheaths 
often bearing conspicuous oral setae; leaf blades broad, lanceolate or ovate; inflorescence 
an open panicle. Spikelets few- to many-flowered, the uppermost floret reduced and 
sterile; disarticulation above the glumes; first glume small, acute, 3-nerved; second 
glume obtuse, 7-nerved; lowermost floret sometimes sterile; lemmas 7-9-nerved, mucro- 
nate or awned; paleas 2-keeled; lodicules 3, unequal; stamens 3; stigmas 2. 

Aulonemia is a tropical American genus of 24 species. The largest 
number of species occurs in Brazil, with others from Guyana to 
Ecuador. Three species occur in Central America and Mexico. (Bam- 
busoideae: Arthrostylidieae.) 

KEY TO SPECIES OF Aulonemia 

la. Leaf blades broadly ovate, 2.7-3.5 x longer than wide; auricular bristles numerous, 
up to 30 mm. long A. patriae 



68 FIELDIANA: BOTANY 

Ib. Leaf blades narrowly ovate, 4.7-6.0 x longer than wide; auricular bristles absent 

A. viscosa 

Aulonemia patriae Pohl, sp. nov. 

Gramen altum, sublignosum, perenne, monocarpicum, ab A. laxa (Maekawa) McClure 
spiculis muticis, gluma inferiore longiore (5-7 mm. vs. 2 mm.), lemmate primo fertili, 
palea lemmatum fertilium lemmatibus aequante, et ab A. viscosa (Hitchc.) McClure 
spiculis longioribus (2.5-4.0 cm. vs. 1.5-2.5 cm.), gluma prima longiore (5-7 mm. vs. 2-5 
mm.), laminis foliorum latioribus, orificio vaginarum setiferarum recedit. 

Perennial, in small clumps of up to 10 culms; culms erect below, to 5 m. long, the lower 
internodes up to 1 m. long, less than 1 cm. thick, naked or with reduced leaf blades; 
culms branching from the middle and upper nodes; branches one per node, diverging 
from the main stem at angles of 30-45 deg. , pushing the leaf sheath away from the main 
stem; upper stem portions scrambling through brush; internodes glabrous, hollow, soft 
and succulent, easily crushed, strongly viscid just below the nodes; a short, thick obconi- 
cal internode, ca. 5-6 mm. long present just above the insertion of each leaf sheath, the 
prophyllum and branch attached at the summit; leaf sheaths glabrous, often purple- 
spotted, viscid at the apex; pseudopetioles flattened, viscid, 5-6 mm. long; sheath apex 
truncate, bearing numerous flattened flexuous bristles up to 30 mm. long; external ligule 
a short, stiff membrane; internal ligule a stiff ciliolate membrane 1.2-2 mm. long; leaf 
blades spreading or drooping, flat, glabrous except for the scabrous margins; tip rather 
abruptly acuminate; blades 20-26 cm. long, 4-8 cm. wide, ovate 2.7-3.5:1, the base 
rounded and asymmetric; undersurface glaucous; prophylla ca. 5 cm. long, with 2 strong 
keels, many-nerved, the smaller nerves occurring both between the keels and on the 
marginal flanges. Peduncles terminal, exserted to 25 cm.; panicles ca. 40 cm. long; 
branches ascending, solitary, to 34 cm. long, their branches strongly divaricate, solitary; 
pedicels solitary, stiff, divaricate, 20-40 mm. long; spikelets relatively few. Spikelets 
2.5-4.0 cm. long, 3-5 mm. wide, linear; first glume ovate 3:1, 5-7 mm. long, 7-nerved; 
second glume 7 mm. long, ovate 3:2, 11-nerved; florets ca. 5; disarticulation above the 
glumes and between the florets; lemmas 13-17 mm. long, awnless, 9-11-nerved, ovate 
3:1, acute, scaberulous on the back; palea as long as the lemma, strongly 2-keeled, the 
keels ciliolate; lateral flanges broad, enveloping the flower; tip bidentate; rachilla inter- 
nodes 6-8.5 mm. long; lodicules 3, brown or purple, obovate, the upper two-thirds of the 
margins ciliolate; anthers ca. 9 mm. long; styles separate; caryopsis cylindric, 8-10 mm. 
long, crowned with the persistent style bases; terminal floret rudimentary, cylindric, ca. 
9 mm. long. 

Aulonemia patriae is similar to A. viscosa of the Talamanca Range 
and A. laxa of Mexico. With the recent discovery of fruiting material 
of all three species, it has been possible to differentiate them. Their 
principal differential characters are given below. 



A. laxa 
A. patriae 
A. viscosa 



Auricular 
bristles 




Palea/ 
lemma 
length 
0.3-0.7 
equal 
equal 


Awn 
length 
(mm.) 
7-10 




Spikelet 
length 
(cm.) 
5.5-7.0 
2.5-4.0 
1.5-2.5 


First glume 


Sterile 
lemmas 
1 




L (mm.) 
2 
5-7 
2-5 


Nerves 
1 
7 
3-5 



BURGER: FLORA COSTARICENSIS 69 

This species occurs in a scattered stand on steep, wet canyon walls of 
the pass at Alto del Roble, just south of the new bridge over the Rio 
Patria (Rio Las Vueltas). The colony consists of possibly several 
hundred individuals, most of them very inaccessible on the steep walls, 
with a few other plants growing on steep embankments north of the 
Rio Patria. I have observed the colony repeatedly since 1968, and saw 
no signs of flowering until 1978. The stems are very soft and succulent 
for a bamboo, and the nodes, upper portions of the sheaths, 
pseudopetioles, and bases of the leaf blades are prominently viscid. 
Flowering occurred prior to June, 1978, when the colony was revis- 
ited. At this time, the entire colony had flowered, and the plants were 
moribund. Most of the spikelets had disarticulated, and many of the 
stems were disarticulating at the nodes. This species presumably has 
been more widespread in the past, since it also occurs on the Cordillera 
de Talamanca. Because the appearance of the vegetative and flowering 
plants is so radically different, I am designating specimens of both 
phases from the type locality as syntypes. 

SYNTYPES: Costa Rica: Prov. Heredia: Alto del Roble, N of 
Heredia, in the pass, just S of the new bridge; elev. 2,000 m., entire 
colony, on both vertical walls of canyon E of road, fruiting and dead or 
dying; old culms disarticulating. Pohl & Gabel 13577. 12 June 1978 
(fruiting); Same locality and colony: Pohl 12798. 8 April 1972 (vegeta- 
tive). Syntypes in ISC. 

Other collections: Costa Rica: Prov. Heredia: Alto del Roble. Pohl & 
Davidse 11781, 30 March 1969; Prov. Cartago: Madre Selva, km. 67, 
along CIA; elevation 2,500 m. Pohl & Davidse 10751. 25 July 1968. 

Aulonemia viscosa (Hitchc.) McClure, Smithsonian Contr. Bot. 
9:61. 1973. Arundinaria viscosa Hitchc., Proc. Biol. Soc. Wash. 40:79. 
1927. Figure 18. 

Caespitose perennial bamboo, the culms solitary or in small clumps from pachymorph 
rhizomes, 4-5 m. tall, 5-15 mm. thick, hollow, glabrous, erect or scrambling, forking, the 
solitary branch at each middle node nearly as thick as the main culm and strongly 
divaricate from it; surface of culms strongly purple spotted or solid purple; nodes con- 
spicuous, very viscid in living plants; sheaths shorter than the internodes, glabrous, 
striate, conspicuously purple spotted; apex of sheath with an erect rounded auricle on 
one side; internal ligule a firm membrane, 1.0-2.5 mm. long; external ligule (exterior to 
the insertion of the pseudopetiole) 0.5-1.0 mm. long, thick; pseudopetiole 5-7 mm. long, 
viscid; leaf blades few, flat, ovate 4.7-6:1, acuminate, 21-26 cm. long, 4-5 cm. wide, the 
bases rounded and oblique; glabrous and dark green above, scaberulous and glaucous 
beneath. Peduncle purple splotched, viscid, as also the rachis and branches of the pani- 
cle; inflorescence apparently terminal, an open pyramidal panicle, 15-25 cm. long; 
branches solitary, naked at the base; spikelets solitary, on elongated stiff flexuous 




JEM 



FIG. 18. Aulonemia viscosa. A, panicle; B, spikelet with sterile terminal floret; C, 
culm internode with a single leaf. 



70 



BURGER: FLORA COSTARICENSIS 71 

pedicels. Spikelets laterally compressed, linear, 1.5-2.5 cm. long, disarticulating above 
the glumes and between the 3-6 florets; glumes 2, the first 3-5 mm. long, lanceolate, 
acute, 3-nerved; second glume 7-9 mm. long, narrowly ovate, blunt-tipped, 7-nerved; 
lemmas narrowly ovate, blunt-tipped, 13-14 mm. long, 7-nerved, internally purple 
spotted; palea equal to the lemma, scabrous on the keels; caryopsis ovoid 4:1, tapering to 
an acuminate apex, dark brown. 

Cerros de Velirla near Copey (TYPE: Tonduz 11729); between Divi- 
sion and Lagunilla; Chirripo Grande. Rare, moist forests between 
1,800-3,000 m. elevation. Recent specimens have all been vegetative, 
and no blooming material has been collected since 1898. Known also 
from Venezuela. 

AVENA Linnaeus 

Caespitose annual grasses; inflorescence a solitary terminal panicle. Spikelets usually 
large, laterally compressed; glumes about as long as the entire spikelet, equal, many- 
nerved, papery; florets several; disarticulation above the glumes and usually between 
the several florets; lemmas rounded on the back, firm, 5-9-nerved; apex 2-toothed; awn 
usually present, originating on the back of the lemma above the middle. (Pooideae: 
Aveneae.) 

Avena sativa L., Sp. PI. 79. 1753. Figure 19. 

Caespitose annual in small clumps; culms ca. 1 m. tall. Inflorescence an open pyramidal 
terminal panicle. Spikelets large, drooping, usually 3.5-4.5 cm. long; glumes equal, 
spreading at maturity, conspicuously nerved; florets usually 2-3, the upper ones shorter 
than the lowermost and the terminal one often abortive; callus sometimes short-bearded; 
back of the lemma glabrous; awn well developed and geniculate or reduced to a short 
rudiment in some strains; cultivated strains disarticulate tardily by a straight line of 
fracture at the base of each lemma. 

Oats is grown as a grain crop in the temperate zone and the grain is 
frequently used for human food in the tropics as a breakfast cereal or in 
drinks. It is rarely cultivated at middle elevations on the volcanoes of 
the Meseta Central as a forage crop for dairy cattle, sometimes mixed 
with Lolium. Common names: avena, "oats." 

AXONOPUS Beauvois 

REFERENCES: G. A. Black, Grasses of the genus Axonopus (a 
taxonomic treatment), L. B. Smith, ed. Advancing Frontiers of Plant 
Sciences 5:vi + 186. 1963. M. C. M. Hickenbick, J. F. M. Vails, F. M. 
Salzano, & M. I. B. de Moraes Fernandes, Cytogenetic and evolution- 
ary relationships in the genus Axonopus (Gramineae), Cytologia 
40:185-204. 1975. 

Perennial or annual Caespitose or rhizomatous, often stoloniferous grasses of low to 
moderate stature. Peduncles 1-several from upper or terminal nodes; inflorescence of 




FIG. 19. Avena saliva. A, panicle; B, spikelet; C, group of florets. 

72 



BURGER: FLORA COSTARICENSIS 73 

several-many digitate or paniculate slender racemes, the spikelets borne in two rows 
along the lower sides of a slender triquetrous or flattened rachis; pedicels very short; 
spikelets appressed to the rachis, each overlapping sequentially with the spikelets next 
above and below it. Spikelets placed with the second glume and back of the fertile lemma 
away from the rachis; first glume absent (except occasionally in A. poiophyllus); second 
glume and lower (sterile) lemma subequal, 2-5-nerved, concealing the upper (fertile) 
floret, slightly or considerably longer than the fertile floret; fertile lemma dorsally com- 
pressed, stiff, cartilaginous, usually faintly striate, glabrous or with a few short spicules 
at its tip, its margins slightly inturned over the equal palea of similar form and texture; 
lodicules 2, truncate; anthers usually 3; styles 2, separate, naked at the base; caryopsis 
flattened, elliptical. 

Axonopus is a large genus of over 100 described species, confined to 
warm climates of the western hemisphere and introduced elsewhere. 
The plants could be confused with some species of Paspalum or 
Digitaria on casual examination. They differ from Paspalum and 
Digitaria in the placement of the spikelets with the fertile lemma away 
from the rachis, and from Digitaria in the presence of solitary spike- 
lets at each node of the rachis. A relatively small number of the species 
have importance as forage grasses. In Costa Rica, A. scoparius 
(Zacate imperial), A. compressus (Zacate amargo), and A. affinis are 
all components of pastures. (Panicoideae: Paniceae.) 

KEY TO SPECIES OF Axonopus 

la. Rachis of racemes beset with numerous elongated, stiff, golden hairs that surround 

spikelets 2 

Ib. Rachis of racemes scabrous or rarely sparsely hairy, lacking conspicuous golden 

hairs 3 

2a. Rachis ca. 0.5 mm. wide, spikelets not sunken into pockets; rachis bearing 

spikelets to the tip A. aureus 

2b. Rachis 1.0-1.5 mm. wide, spikelets sunken into pockets between the midrib and 
margin; rachis extended beyond the ultimate spikelet as a flattened naked point 
2-3 mm. long, sometimes with a solitary abortive spikelet at its tip 

A, chrysoblepharis 

3a. Spikelets 1.2-1.6 mm. long; weak caespitose annual; culms 20-40 cm. tall 

A. capillaris 
3b. Spikelets 1.8-3.5 mm. long; perennials with hard bases, often rhizomatous or 

stoloniferous 4 

4a. Inflorescence of very numerous racemes (up to 100), racemose along rachis, up 

to 50 cm. long; internodes of culms up to 7 mm. thick A. scoparius 

4b. Inflorescence of 2-8 racemes borne on short common rachis; internodes of culms 

3 mm. or less thick 5 

5a. Spikelets 1.8-2.2 mm. long A. purpusii 

5b. Spikelets 2.3-3.5 mm. long 6 

6a. Second glume exceeding fertile floret by 0.2 mm. or less; nerves of bracts 
obscured by dense bands of silky pubescence 7 



74 FIELDIANA: BOTANY 

6b. Second glume exceeding fertile floret by 0.2-1.2 mm.; nerves of bracts not 

obscured by pubescence 8 

7a. Culm internodes 1-3, not entirely covered by leaf sheaths; spikelets 2.9-3.1 mm. 
long; bracts 2-nerved; anthers 1.5-1.8 mm. long; coastal savannas, Guanacaste 

A. poiophyllus 

7b. Culm internodes numerous, short, culms clothed by overlapping sheaths nearly to 
peduncle; spikelets 3.0-3.5 mm. long, bracts 4-5-nerved; anthers 2.2 mm. long; 

Volcan Rincon de la Vieja A. volcanicus 

8a. Fertile floret 1.0-1.2 mm. shorter than the spikelet; second glume 3-nerved, 
lateral nerves projecting as short points, apex of the glume trifid; spikelets 

3.0-3.6 mm. long A. centralis 

8b. Fertile floret 0.3-0.7 mm. shorter than spikelet; second glume 2- or 4-nerved, 

lateral nerves not projecting; spikelets usually 2.4-2.7 mm. long 9 

9a. Leaf blades linear with very blunt, rounded tips; fertile floret up to 0.4 mm. shorter 

than second glume; middle elevations, mostly in the Meseta Central . . A. affinis 

9b. Leaf blades narrowly ovate, tapering from middle to an acute tip; fertile floret 

0.3-0.6 mm. shorter than second glume; widespread at lower and middle elevations 

A. compressus 

Axonopus affinis Chase, J. Wash. Acad. Sci. 28:180. 1938. 

Perennial, caespitose or with stolons; culms unbranched, 20-60 cm. tall; internodes up 
to 2 mm. thick, pithy, glabrous; nodes glabrous or slightly bearded; sheaths compressed, 
glabrous except for the ciliate overlapping margin, the inner margin thin and fragile; 
ligule a ciliolate membrane, in total 0.3-0.5 mm. long; leaf blades linear, flat or folded, 
4-15 cm. long, 3-5 mm. wide, papillose-ciliate near the base, otherwise glabrous, the 
apex obtuse. Peduncles 1-2 from the terminal sheath, exserted up to 16 cm.; inflores- 
cence 5-11 cm. long, of 2-7 divergent racemes on a short common rachis; individual 
racemes slender, 3.5-5.0 cm. long; rachis triquetrous, ca. 0.5 mm. wide, scabrous on the 
angles; spikelets subsessile, the pedicels less than 0.2 mm. long; spikelets overlapping 
sequentially one-third to one-half of their length. Spikelets 2.3-2.8 mm. long, elliptic- 
obovate, 2.4-2.7:1, acute, slightly pubescent on the margins of the glume and sterile 
lemma and at the apex; second glume and lower (sterile) lemma equal, exceeding the 
floret by 0.2-0.4 mm.; nerves 2, submarginal, the midnerve lacking; fertile floret 
stramineous; lodicules 2, truncate; anthers 3, purple, ca. 1.5 mm. long; styles 2, sepa- 
rate, naked at the base; stigmas 2, purple. 

Pastures and open areas, mostly 1,700-2,200 m. elevation; Vara 
Blanca, Volcan Barba, San Ramon, Tarbaca. June to December. Wide- 
spread, southeastern United States to Argentina; introduced 
elsewhere. 

This species, along with A. compressus, comprises an intricate and 
difficult taxonomic group, as yet poorly understood. My treatment 
should be regarded as tentative. I have named as A. affinis our speci- 
mens that have a chromosome number of n = 50 and which possess 
linear rather than narrowly ovate leaf blades. All have outer bracts 
that only slightly exceed the fertile lemma. Presence or absence of 



BURGER: FLORA COSTARICENSIS 75 

stolons, often used as a character in Axonopus, is unreliable, as plants 
in dense turf, like those in pastures, frequently lack stolons. 

Axonopus aureus Beauv., Ess. Nouv. Agrost. 12. 1812. A. chry sites 
(Steud.) Kuhlm., Comm. Linh. Telegr. Estrat. Mato Grosso Amazonas 
67, Annexo 5, Bot. pt. 11:88. 1922. Panicum chrysites Steud., Syn. PI. 
Glum. 1:38. 1854. Figure 20. 

Caespitose perennial in clumps from knotty crowns; plants 40-90 cm. tall, branching 
from the lower nodes, much of the foliage borne toward the base; internodes 1.0-1.5 mm. 
thick, hollow, glabrous, rarely with a few short golden bristles near the apex; nodes 
glabrous, dark, not prominent; lower sheaths overlapping, the upper shorter than the 
internodes, keeled, glabrous or papillose-hispid, the margins usually ciliolate; ligule a 
dense ciliolate fringe, usually less than 0.5 mm. long; leaf blades 8-15 cm. long, 4-7 mm. 
wide, glabrous or the margins and sometimes the surfaces papillose-hispid, a dense tuft 
of long hispid hairs occasionally just behind the ligule. Peduncles solitary, exserted 2-15 
cm., terminal on erect leafy branches. Panicle vase-shaped, up to 9 cm. long, made up of 
2-9 slender ascending racemes borne on a short central axis; racemes 4-9 cm. long; rachis 
triquetrous, ca. 0.5 mm. wide, strongly papillose-ciliate with stout golden hairs 2-3 mm. 
long; tufts of similar hairs borne on a transverse ridge just below the insertion of each 
spikelet; pedicels less than 0.2 mm. long; spikelets subsessile in shallow excavations of 
the rachis, in 2 alternating rows on the 2 lower sides, each overlapping the next above by 
about one-third of its length. Spikelets elliptic-obovate 2:1, biconvex, glabrous, 1.2-1.5 
mm. long; second glume and lower (sterile) lemma equal, as long as the spikelet, gla- 
brous, usually purple, faintly 2-3-nerved; upper (fertile) lemma elliptical, cartilaginous, 
1.2-1.3 mm. long, chestnut-colored, the palea similar, bulging; lodicules 2, truncate; 
anthers 3, purple, 0.8-0.9 mm. long; styles 2, separate; lodicules 2. Chromosome number 
n = 10 from a Costa Rican specimen. 

Dry Curatella-Byrsonima savannas, and other open areas, espe- 
cially on volcanic tuff, 200-1,100 m. elevation; occasional in Guanacaste, 
western Meseta Central (Hda. Argentina, Nuestro Amo, Rodeo de 
Pacaca, Paraiso); Buenos Aires, Boruca, Canas Gordas. October to 
January. Mexico to Panama; northern South America to Brazil and 
Bolivia; West Indies. 

Black has applied the name A. chrysites to this species, deeming the 
name A. aureus dubious. However, Chase (Proc. Biol. Soc. Wash. 
24:135. 1911) discussed the application of the name A. aureus and fixed 
it in the sense used here. 

Axonopus capillaris (Lam.) Chase, Proc. Biol. Soc. Wash. 24:133. 
1911. Paspalum capillare Lam., Tabl. Encycl. 1:176. 1791. Figure 23. 

Plants annual, caespitose, rather delicate; culms mostly 20-40 cm. long, often genicu- 
late at the base and sprawling, branching freely from the base and lower nodes; inter- 
nodes slender, 0.7 mm. or less thick, hollow, glabrous; nodes glabrous or minutely 
bearded; leaf sheaths shorter than the internodes, glabrous except for the short-ciliate 
overlapping margin; ligule a densely ciliolate membrane, 0.3-0.5 mm. long; leaf blades 




FIG. 20. Axonopus species. A. aureus: A, culm and inflorescence; B, C, rachis and 
spikelets; A. chrysoblepharis: D, E, tip of rachis and spikelets. 



76 



BURGER: FLORA COSTARICENSIS 77 

flat, tapering from a broad base, 1.5-7.0 cm. long, 3-7 mm. wide, the length 5-12 x the 
width, glabrous except for a few marginal cilia near the base. Peduncles slender, 
arcuate, 1-3 from the terminal sheath and sometimes others from the upper leaf axils, 
exserted up to 15 cm.; inflorescence of 2 conjugate divergent racemes 2.0-3.5 cm. long 
borne at the apex of the peduncle, often a third borne a short distance below; racemes 
very slender, the triquetrous rachis less than 0.5 mm. wide, scabrous on the angles, 
undulate; spikelets borne in 2 rows on the lower 2 sides of the rachis, each one barely 
overlapping the base of the next above in sequence. Spikelets obovate 2.3-2.5:1, min- 
utely puberulent, 1.2-1.6 mm. long, stramineous or purplish; second glume as long as the 
spikelet, 4-nerved, lacking a midrib; sterile lemma similar, 2-nerved; upper (fertile) 
lemma about as long as the spikelet, faintly striate, its palea similar; anthers 3, purple, 
0.4 mm. long; styles 2, separate; stigmas purple; caryopsis amber, elliptical 2:1, 1.1 mm. 
long. Chromosome number n = 10, 20 from Costa Rican specimens. 

Somewhat weedy; beaches, roadsides, pastures. Playas del Coco, 
San Ramon area, Turrucares, Alajuela, San Jose. September to 
January. Honduras and El Salvador, Costa Rica and Panama to north- 
ern South America, southward to Peru, Brazil, and Paraguay; Lesser 
Antilles. 

Black (1963) states that some specimens have pilose foliage, but ours 
are nearly glabrous. 

Axonopus centralis Chase, J. Wash. Acad. Sci. 17:143. 1927. Figure 
24. 

Caespitose perennial; culms 35-80 cm. tall, erect or spreading, unbranched; internodes 
1.5-3.0 mm. thick, pithy, glabrous; nodes glabrous or minutely woolly; leaf sheaths 
keeled, longer than the internodes, the overlapping margin ciliate, the other margin 
very thin and fragile; collar more or less pubescent; ligule a minute ciliolate rim, 0.2-0.3 
mm. long; leaf blades rather thin, flat, 8-50 cm. long, 8-13 mm. wide, papillose-ciliate at 
the base and with occasional appressed hairs on the upper surface. Peduncles 1-2 from 
the uppermost sheath, slender and arcuate, exserted up to 27 cm., slightly woolly at the 
apex; inflorescence usually of 2-3 ascending racemes borne on a common rachis up to 6 
cm. long; racemes slender, 7-13 cm. long; rachis triquetrous, the spikelet-bearing sides 
ca. 0.7 mm. wide, the third side narrower; spikelets overlapping sequentially about 
one-third. Spikelets 3.4-3.6 mm. long, very flat, ovate 3.1-3.5:1, the apex rather blunt; 
second glume trifid at the tip, the 2 lateral nerves exserted as short points; lateral nerves 
submarginal, flanked on both sides by a silky band; midnerve usually present but faint; 
lower (sterile) lemma similar to the glume but slightly shorter, the apex acute; upper 
(fertile) floret much shorter than the outer bracts, 1.9-2.1 mm. long, elliptical 2.1:1, 
glabrous, stramineous; palea similar to the lemma; anthers 3, brownish and shriveled, 
ca. 0.6 mm. long; caryopsis elliptical, 2.0-2.5:1, tan, 1.4-1.6 mm. long. 

In light shade, northwestern Guanacaste, Hda. Las Animas, Hda. 
Palo Verde, Finca la Pacifica, Playa Tamarindo; elevations from sea 
level to 200 m. June to December. Southwestern Mexico to Panama; 
Ecuador to Venezuela. 

In several of the specimens examined, the anthers were trapped 



78 FIELDIANA: BOTANY 

within the fertile floret at the apex of a well-developed caryopsis. They 
were shriveled and contained shrunken or empty pollen grains. It is 
probable that this species is apomictic or cleistogamous. 

Axonopus chrysoblepharis (Lag.) Chase, Proc. Biol. Soc. Wash. 
24:134. 1911. Cabrera chrysoblepharis Lag., Gen. & Sp. Nov. 5. 1816. 
Figure 20. 

Duration indefinite, possibly annual; caespitose; plants 70-100 cm. tall, erect; culms 
branching freely from lower and middle nodes; internodes 1-2 mm. thick, hollow, gla- 
brous, golden colored; nodes glabrous or bearded with short golden hairs; leaf sheaths 
nearly glabrous to pilose or pustulose-hispid; ligule a ciliolate membrane, 0.3-1.2 mm. 
long; leaf blades flat, 5-30 cm. long, up to 15 mm. wide, marginally pustulose-hispid, the 
surfaces more or less pilose and sometimes papillose-hispid as well. Peduncles terminal 
on the main culm or leafy erect branches, exserted 7-26 cm.; inflorescence a vase-shaped 
group of 4-10 slender ascending racemes borne on a short common rachis 1-2 cm. long. 
Rachis of individual spikes triquetrous, the back side 1-1.5 mm. wide, with a conspicuous 
flattened midrib and thickened margins that are densely pustulose hispid-ciliate with 
conspicuous golden hairs 2-3 mm. long; midrib produced between the spikelets as a 
thickened corky ridge, also bearing pustulose hairs; tip of rachis prolonged beyond the 
spikelets as a naked flattened point 2-3 mm. long, sometimes bearing a solitary abortive 
spikelet on its tip; spikelets sunken into cavities between the midrib and margins of the 
rachis, each spikelet overlapping the next in sequence by about one-half. Spikelets 
1.4-1.6 mm. long, ovate 2.1-2.7:1; second glume and sterile lemma similar, with 2 sub- 
marginal nerves, equal in length and barely exceeding the fertile floret; texture of bracts 
very thin, revealing the brown color of the fertile floret; fertile lemma brown, 1.3-1.5 
mm. long; anthers 3, purple, 0.5-0.6 mm. long; styles 2, separate; stigma purple. 
Chromosome number n = 10 or 10 + 2b from Costa Rican and Venezuelan specimens. 

Rare; dry savannas. We have seen Pittier & Tonduz specimens col- 
lected before 1900 from Boruca, Mano de Tigre, and Canas Gordas. 
Our sole recent specimen was from the Boruca savannas. November to 
February. Guatemala to Panama and northern South America, to 
Peru, Bolivia, Brazil, and Paraguay; Trinidad. 

Axonopus compressus (Swartz) Beauv., Ess. Nouv. Agrost. 154. 
1812. Milium compressum Swartz, Prodr. Veg. Ind. Occ. 24. 1788. 
Figure 21. 

Perennial; stoloniferous or caespitose (especially when crowded in turf), usually 
branching from the base or from rooted stolons; culms 1-3 mm. thick; internodes gla- 
brous, hollow; nodes glabrous or appressed bearded; sheaths keeled, usually glabrous but 
the overlapping margin ciliate, the collar often with a pubescent line; ligule a short 
ciliolate membrane, in total 0.2-0.5 mm. long; leaf blades flat, thin or firm, 8-26 cm. long, 
7-13 mm. wide, narrowly ovate, tapering from below the middle to an acute apex, 
papillose-ciliate on the lower margins and sometimes with scattered weak appressed 
hairs on the upper surface. Peduncles 1-2 from the uppermost sheath, exserted up to 17 
cm.; inflorescence of 2-6 divergent slender racemes borne on a short common rachis; 
pedicels very short, usually less than 0.2 mm. long. Spikelets overlapping sequentially 
one-fourth to one-third of their length, 2.4-2.7 mm. long, ovate, acute, the second glume 




FIG. 21. Axonopus compressus. Plant with inflorescences, spikelet, and fertile floret. 



79 



80 FIELDIANA: BOTANY 

and lower (sterile) lemma 0.3-0.7 mm. longer than the upper (fertile) floret; both bracts 
with 2 submarginal nerves and more or less pilosity along both sides of the nerves; fertile 
lemma stramineous, its palea similar; lodicules 2, truncate; anthers 3, purple; caryopsis 
tan or white, elliptical, 1.0-1.6 mm. long, flattened. 

Widespread and common in pastures and open areas, open shade, 
usually in moist sites; sea level to 1,400 m. Probably blooming year- 
long. Widespread in warmer parts of the World. 

Axonopus compressus is complex and highly variable, with many 
morphological races and several chromosomal levels. It is unlikely that 
this and related species can be properly understood without extensive 
cytological, genetic, and cultural studies. My treatment should be re- 
garded as tentative. Among our specimens that have known chromo- 
some numbers, I have been able to recognize roughly several groups 
based upon chromosome numbers and morphology; however, many 
cytologically unknown specimens can only be placed very approxi- 
mately with one or another of these groups. Descriptions of the princi- 
pal differences among these cytotypes are given below. 

n = 40. Plants 45-135 cm. tall; leaf blades 12-22 x longer than wide; 
spikelets ovate 2.7-2.8:1; anthers 1.0-1.3 mm. long. Known Costa 
Rican specimens are from elevations above 1,300 m. in the Meseta 
Central. 

n = 20. Plants 20-60 cm. tall; leaf blades mostly 8-11 x longer than 
wide, thin; spikelets ovate, 2.8-3.3:1; anthers 0.5-0.7 mm. long, brown 
to purplish. Widespread, sea level to 1,100 m. elevation. 

n = 30. One specimen so determined from the Siquirres area (Pohl 
& Davidse 11463) has heavily bearded nodes and leaf blades promi- 
nently ciliate for their full length; second glume 4-nerved. 

Axonopus poiophyllus Chase, Proc. Biol. Soc. Wash. 24:133. 1911. 
A. blakei Hitchc., Proc. Biol. Soc. Wash. 40:85. 1927. A. rhizomatosus 
Swallen, J. Wash. Acad. Sci. 23:458. 1933. Figure 22. 

Perennial, caespitose or with short, knotty rhizomes; culms 25-100 cm. tall, erect, 
unbranched; foliage mostly basal, the lower sheaths overlapping; culm internodes 1-3, up 
to 3 mm. thick, hollow; nodes appressed-bearded; leaf sheaths keeled, more or less 
papillose-hirsute above the nodes and at the apex; overlapping margins ciliate; ligule a 
minute ciliate fringe, 0.3-0.5 mm. long; leaf blades flat or folded, 13-33 cm. long, up to 5 
mm. wide, the uppermost one much reduced. Peduncles solitary or 2 from the upper- 
most sheath, exserted 6-25 cm.; inflorescence of 3-7 ascending racemes borne on a 
common axis up to 4 cm. long; racemes up to 11 cm. long, the slender triquetrous 
undulate rachis ca. 0.5 mm. wide, scabrous and with a few scattered elongate hairs; 
spikelets borne on short pedicels less than 0.5 mm. long; spikelets overlapping sequen- 
tially about one-third, 2.5-2.8 (-3.1) mm. long, ovate 2.9-3.1:1; first glume absent or if 




JF/I 



FIG. 22. Axonopus species. A. purpusii: A, inflorescence; B, base of plant; C, portion 
of raceme with spikelets; A. poiophylltis: D, inflorescence; E, portion of raceme with 
spikelets. 



81 



82 FIELDIANA: BOTANY 

present, narrowly triangular, up to 2.5 mm. long, 1-5-nerved; second glume and lower 
(sterile) lemma equal, as long as the spikelet, 2-nerved, silky near the margins and at the 
base; upper (fertile) lemma slightly shorter than the outer bracts, ovate 2.7-2.8:1, faintly 
striate, ciliate at the tip; anthers 3, purple, 1.5-1.8 mm. long; styles 2, separate; stigmas 
purple. Chromosome number n = 30 from Costa Rican and Honduran specimens. 

Dry Curatella-Byrsonima savannas on volcanic tuff, mostly at ele- 
vations under 200 m.; northern Guanacaste south to Bagaces. June to 
July; January. Southern Mexico to Honduras; Colombia; Cuba. 

We have previously confused this species with the endemic A. vol- 
canicus from Rincon de la Vieja. In addition to the differences stated 
in the key, they differ in chromosome number. Spikelets in the genus 
Axonopus lack a first glume, and the occurrence of this structure in 
some of our specimens of A. poiophyllus is apparently unique. 

Axonopus purpusii (Mez) Chase, J. Wash. Acad. Sci. 17:144. 1927. 
Paspalum purpusii Mez, Bot. Jahrb. 56, Beibl. 125:10. 1921. 
Axonopus anomalus Swallen, Contr. U.S. Natl. Herb. 29:268. 1949. 
Figure 22. 

Densely caespitose perennial; culms 50-80 cm. tall, erect, simple; internodes 1-2, elon- 
gated, less than 1 mm. thick, glabrous; nodes dark, not enlarged, glabrous or rarely 
sparsely appressed-bearded; foliage mostly basal, the culms rather naked; sheaths 
keeled, much shorter than the internodes, glabrous to densely pilose, the overlapping 
margin ciliate; ligule a densely ciliate rim, in total 0.3-0.6 mm. long; collar usually pilose; 
blades 15-25 cm. long, 2-4 mm. wide, more or less papillose-pilose, the tip abruptly 
rounded; uppermost blade usually much reduced; basal foliage frequently burned off in 
herbarium specimens. Peduncles 1-2, exserted 12-17 cm. from the apical sheath, very 
slender; inflorescence 8-11 cm. long, vase-shaped, of 3-6 slender ascending racemes 
borne on a short common rachis 1-3 cm. long; racemes 4-8 cm. long, woolly at the base; 
rachis slender, 0.3-0.5 mm. wide, undulate, scabrous on the angles and with scattered 
long hairs at the nodes; spikelets subsessile, the pedicels 0.3 mm. or less long. Spikelets 
overlapping sequentially for one-third to one-half their length, 1.8-2.2 mm. long, 
oblong-ovate 2.5-3.3:1; second glume and lower (sterile) lemma similar, as long as the 
spikelet, 2-nerved submarginally, the nerves mostly concealed by dense silky appressed 
hairs that extend to 0.3 mm. beyond the acute tip of the bracts; upper (fertile) lemma 
ovate ca. 2.4:1, stramineous, faintly striate, with a few minute spicules at its tip; palea 
similar; lodicules 2, truncate; anthers 3, purple, 1.2 mm. long; styles 2, separate; stigmas 
light-colored. Chromosome number n = 10 from a Costa Rican specimen. 

Dry savannas, especially with Curatella and Byrsonima; northern 
Guanacaste, between Liberia and La Cruz; savannas of Buenos Aires; 
elevations 75-380 m. March to August. Southern Mexico to Panama; 
northern South America to Bolivia, Brazil, Paraguay, and Argentina. 

Axonopus scoparius (Fliigge) Kuhlm., Comm. Linh. Telegr. Es- 
trat. Mato Grosso Amazonas, Publ. 67, Annexe 5, Bot. 11:45. 1922. 
Paspalum scoparium Fliigge, Gram. Monogr. 124. 1810. Figure 23. 




FIG. 23. Axonopus species. A. scoparius: A, inflorescence; B, spikelets, both sides; A. 
capillaris: C, blooming plant; D, spikelets, both sides. 



84 FIELDIANA: BOTANY 

Tall, vigorous perennial from a matted crown; culms erect, to 1.5 m. tall; plants 
sometimes producing lengthy coarse stolons when pendent on steep slopes; culms occa- 
sionally branched; internodes up to 7 mm. thick, solid, pithy, glabrous; lower leaf 
sheaths closely overlapping, strongly keeled, glabrous; ligule a thick membrane, bearing 
short cilia, in total 1.0-2.7 mm. long; dewlap conspicuous, yellowish; collar bearing a line 
of short, stiff hairs; leaf blades flat, 15-50 cm. long, 0.5-3.0 cm. wide, tapering to an acute 
apex; lower surface glabrous; upper surface papillose-hirsute. Peduncle included or ex- 
serted up to 30 cm.; inflorescence a terminal panicle made up of numerous simple or 
rarely branched spreading or ascending racemes; panicle open, dome-shaped, often 
purplish, usually 15-30 cm. long and nearly as wide; individual racemes to 12 cm. long; 
rachis of racemes slender, triquetrous, strongly scabrous on the angles and sometimes 
with a few longer hairs; pedicels stiff, appressed, scabrous, less than 1 mm. long; spike- 
lets borne in 2 rows appressed to the lower sides of the rachis; successive spikelets 
overlapping by about one-third. Spikelets 2.7-2.9 mm. long, ovate 2.5-3.3:1, acute or 
rather blunt, usually purple; second glume and lower (sterile) lemma equal, as long as 
the spikelet, covering and concealing the upper (fertile) floret, both sparsely appressed 
pubescent between the nerves; upper (fertile) floret 2.2-2.4 mm. long, oblong, rather 
blunt; lemma cartilaginous, stramineous, its apex bearing a few minute spicules, the 
margins slightly inrolled over the edges of a similar palea; lodicules 2, truncate; anthers 
3, purple, 1.5-1.7 mm. long; styles 2, stigmas purple. Chromosome numbern = 10 from 
Costa Rican specimens. 

This species is widely cultivated in moister parts of the Meseta 
Central and on the volcanoes of the Cordillera Central, at elevations up 
to 2,500 m. It appears to persist after cultivation or to spread freely to 
field margins and road embankments. Black reports A. scoparius from 
Mexico to Peru, without indicating whether part of this range is due to 
spread in cultivation. 

None of our specimens has mature seed, and caryopses are appar- 
ently rarely produced. In cultivation, the plants are reproduced by 
cuttings or by placing culms in furrows as is done with sugar cane. 

The species is widely cut as green feed for dairy cattle and produces 
tremendous yields of forage under optimum conditions. Common 
name: Zacate Imperial. We have seen a strain with purple leaves 
cultivated near Pacayas. 

Axonopus volcanicus Pohl, sp. nov. Figure 24. 

Axonopus poiophyllo Chase similis, sed ab eo folii numerosis (6-11), vaginis imbricatis, 
spiculis longioribus (3.0-3.5 mm.), nervis glumae secundae et lemmatis sterilis 4-5, num- 
ero chromosomico n = 19 recedens. 

Densely caespitose perennial, forming thick sods; culms erect, 30-80 cm. tall, branch- 
ing freely from the base and lower nodes; internodes compressed, to 3 mm. thick, hollow 
with a small lumen or solid and pithy, glabrous; leaf sheaths keeled, closely overlapping 
and clothing most of the culm; collar, keel, and margins silky ciliate, especially near the 
apex; ligule a minute membrane, densely ciliate with silky white hairs, in total 0.7-0.9 
mm. long; leaf blades 6-11 per culm, 9-20 cm. long, 4-7 mm. wide, long-pubescent on the 




FIG. 24. Axonopus species. A. volcanicus: A, inflorescence; B, spikelets, both sides; 
C, culm invested with leaves; A. centralis: D, inflorescence; E, spikelets, both sides. 



86 FIELDIANA: BOTANY 

upper surface above the ligule; margins papillose-ciliate with long coarse hairs to 4 mm. 
long; midrib sometimes pubescent above; margins scaberulous; midrib prominent be- 
neath; tip of blade blunt, boat-shaped. Peduncles exserted 6-15 cm.; inflorescences 1-2 
from the terminal sheath; composed of 3-8 ascending racemes borne on a common rachis 
1-3 cm. long; inflorescence 6-14 cm. long, the individual racemes 6-13 cm. long, minutely 
bearded at the base, spikelet-bearing nearly to the base; rachis triquetrous, ca. 0.5 mm. 
wide, scabrous on the angles and with a few scattered elongated papillose-based hairs; 
pedicels 0.3-0.5 mm. long. Spikelets overlapping sequentially about one-third their 
length, 3-3.5 mm. long, ovate 2.8-3.1:1, silky on the margins of the bracts and at the 
base, often purplish; second glume and lower (sterile) lemma equal, as long as the 
spikelet and slightly exceeding the tip of the fertile lemma, 4-5-nerved, the nerves 
usually submarginal, a weak midrib present or absent; upper (fertile) lemma 2.5-3.1 mm. 
long, elliptic, stramineous, faintly striate, with a tuft of short cilia at the tip; palea 
similar; lodicules 2, truncate, fleshy; anthers 3, purple, 2.2 mm. long; styles 2, separate; 
stigmas purple. Immature caryopses seen. 

A large, dense stand of this species occurs above timberline on the 
west face of Rincon de la Vieja, at a locality on Hacienda Guachipelin 
known as Los Copelares. It also occurs around a fumarole called Las 
Hornillas. In both cases, chromosome counts indicate n = 19. We have 
previously considered that these plants were conspecific with A. 
poiophyllus Chase, which, according to our counts, has 30 pairs of 
chromosomes. Both populations, however, differ from that species in 
having longer, more densely silky spikelets with 4-5 nerves on the 
bracts, typical A. poiophyllus having 2-nerved bracts. More strik- 
ingly, the montane A. volcanicus has a much larger number of foliage 
leaves per culm, their sheaths densely clothing the stems nearly to the 
inflorescence. Axonopus poiophyllus typically has 1-3 culm blades and 
more or less exposed internodes. None of our specimens has spikelets 
with first glumes, while the common lowland A. poiophyllus in the 
region frequently has them. The peculiar aneuploid chromosome 
number of A. volcanicus suggests that it is a recent derivitive that is 
successful in the rather extreme habitats of Rincon de la Vieja. 

SPECIMENS SEEN: HOLOTYPE: Costa Rica; Prov. Guanacaste, 
La Hornillas, Volcan Rincon de la Vieja, Hda. Guachipelin, elevation 
750 m., 17 January 1969, n = 19, Pohl & Davidse 11667, ISC 277812. 
OTHER SPECIMENS: Prov. Guanacaste, Los Copelares, Volcan 
Rincon de la Vieja, Hda. Guachipelin, above timberline on W side of 
volcano, elevation 1,400 m., 30 July 1971, n = 19, Pohl 12662. Another 
sheet from the same locality: Burger & Pohl 7763. 

BAMBUSA Schreber 

Caespitose bamboos of medium to tall stature; culms hollow or sometimes nearly 
solid; culm sheaths early deciduous; branches unarmed or with stout straight or hooked 



BURGER: FLORA COSTARICENSIS 87 

branch thorns; branches 1-several per node, one usually larger than the others; foliage 
blades without conspicuous commissural veins. Inflorescence spicate, of sessile, clus- 
tered pseudospikelets, these with basal prophylla and bracts, the lower glumelike, en- 
closing branch buds and short paleas or true spikelets; pseudospikelets continued with- 
out interval into several-flowered spikelets, their lemmas many-nerved, the paleas about 
as long as the lemma; lodicules 3, flat, vasculated, ciliate; anthers 3 or 6; style 1, stigmas 
2 or 3. 

As treated by McClure (1973), thorny American bamboos previously 
considered as constituting the genus Guadua Kunth, are here included 
as subgenus Guadua (Kunth) McClure. Subgenus Bambusa consists of 
Asiatic bamboos, either thorny or not, many of which are cultivated in 
the American tropics. In addition to the species treated here, others 
may be found in cultivation. (Bambusoideae: Bambuseae.) 

KEY TO SPECIES OF Bambusa 

la. Culm branches with straight or hooked thorns; internodes not striped 2 

Ib. Culm branches lacking thorns; culms usually longitudinally striped with green and 

yellow B. vulgaris 

2a. Culms up to 3 cm. thick, 5 m. tall; pseudopetioles less than 1 mm. long, leaf 
blades 10 mm. or less wide; native, dry savannas, northern Guanacaste 

B. paniculate, 

2b. Culms up to 15 cm. thick, 30 m. tall; pseudopetioles 2-5 mm. long, leaf blades 
10-18 mm. wide; cultivated Asiatic species B. arundinacea 

Bambusa arundinacea Willd., Sp. PL 245, 1799, sensu Gamble, 
Ann. Roy. Bot. Card. Calcutta 7:51, pi. 48. 1896. Figure 25. 

Giant caespitose bamboos in large dense clumps; culms up to 30 m. tall and 10-15 cm. 
thick, nearly erect; internodes cylindrical, green, densely glaucous when young with 
siliceous powder, lower nodes ciliate with brown hairs; culm sheaths deciduous, coriace- 
ous, glabrous outside, sheath blades as wide as the sheath apex, broadly triangular, 
erect, the abaxial surface glabrous, the adaxial surface densely hispid with blackish 
hairs; ligule a short thick ciliolate membrane, 1-2 mm. long; lower nodes of the culms 
producing numerous weak spreading thorny branches; foliage-bearing branchlets 1-3 per 
node, solid, frequently with 1-several straight or hooked thorn-branches arising at their 
bases; sheaths on foliage-bearing branchlets overlapping, glabrous except for the cilio- 
late margin; auricles ciliate with light-colored bristles up to 6 mm. long; external ligule 
prominent, coriaceous; pseudopetioles 2-5 mm. long; margins of blades white-banded; 
surfaces glabrous, slightly glaucous, 7-18 cm. long, 10-18 mm. wide, leaves crowded 
towards the tips of the branchlets, the sheaths overlapping. Inflorescences large, 
covering at least the terminal 5 m. of the culms; pseudospikelets subsessile, 1.5-2.0 cm. 
long, their bases enclosed by prophylls, clustered at the nodes of slender naked branch- 
lets up to 50 cm. long, usually 2-5 per node of the slender rachis, with several short 
prophylla at the base, branching into true spikelets that are continuous with the basal 
bracts and prophylls; prophylla 4-5 mm. long, ciliate on the keels, no definite "glumes" 
above the basal bracts; true spikelets disarticulating above the basal bracts and between 
florets; lemmas broad, ca. 15-nerved, rounded on the back, mucronate, 8-9 mm. long, the 
margins short-ciliate, enwrapping the rachilla at the base; palea conspicuously ciliate on 




FIG. 25. Bambusa arundinacea. A, pseudospikelet; B, portion of inflorescence; C, 
twig node with branch thorns; D, base of seedling. 



BURGER: FLORA COSTARICENSIS 89 

the keels, as long as the lemma or slightly longer; rachilla internodes short, flattened; 
florets 5-7, the uppermost reduced; lodicules 3, flattened, vasculated, broadly spatulate, 
long-ciliate at the tip; anthers 6, yellow, 4-5 mm. long; style 1; stigmas 3, plumose; 
caryopsis plump, ovate-fusiforme, acute, tan, 7.0-7.5 mm. long, 2.5 mm. wide; embryo 
1.5 mm. long; style base persistent; adaxial groove conspicuous, running the full length 
of the caryopsis. 

The above inflorescence and spikelet description was taken from a 
specimen collected by Mayra Montiel de B., 13 May 1974. I have vis- 
ited the same colony on the estate of Dr. Antonio Pena Chavarria in 
Rio Segundo. The clump was dense, 10-12 m. in diameter and the 
erect to arching culms reached 20-30 m. in height. Individual culms 
were 10-12 cm. thick. The internodes of young culms were densely 
whitened with siliceous powder (tabasheer). This clump began to 
bloom in 1974 and the specimen collected by Sra. Montiel de B. in May 
had intact inflorescences. When I saw it in December 1974, most of the 
clump was still vegetative, but many culms were dead and the 
spikelets had shattered. The gardener stated that the clump was at 
least 25 years old and that this was the first flowering. The plants 
produced prodigious quantities of fallen spikelets. Many of the florets 
were sterile and empty. An analysis of florets collected under this 
clump, performed by the Iowa State Seed Laboratory, indicated that 
nearly 20 per cent of the material contained caryopses. Enough 
caryopses were produced that the seedlings constituted a weed prob- 
lem in the flower beds near the clump. Seedlings 25-30 cm. tall were 
already present and were producing short rhizomes or tillers. 

This species, of Asiatic origin, is occasionally cultivated in Central 
America, but is disliked because of the thorns. A large clump occurs in 
the bamboo grove of the CATIE of Turrialba. Blooming during the 
1974-1975 period is known from Panama and other parts of Central 
America. 

Bambusa paniculata (Munro) Hack., Oesterr. Bot. Z. 53:195. 1903. 
Guadua paniculata Munro, Monogr. Bamb. 85. 1868. Figure 26. 

Long-lived perennial bamboo; blooming rare; plants caespitose in dense clumps of 
10-20 culms; culms 5-10 m. tall, erect below, the upper portions stiffly arching, branching 
freely from the middle and upper nodes, the branches spreading horizontally; culms up 
to 2.5 cm. thick, very thick-walled or solid, green when immature, yellow at anthesis; 
internodes cylindrical, grooved on the side toward the bud or branch; nodes with a 
prominent sheath girdle and swollen supranodal ridge; apex of internodes appressed- 
velvety; one principal branch per node, accompanied by 1-2 smaller ones and stout 
straight thorn branches up to 2 cm. long. Primary branches from culms spreading, their 
naked internodes hollow, bearing secondary leaf-bearing branches in clusters of 6-10, 
their internodes retrorsely puberulent; sheaths ciliolate on the overlapping margins; 
auricles truncate, bearing numerous brownish flexuous bristles up to 7 mm. long; 




FIG. 26. Bambusa paniculate. A, spikelet-bearing branches with nodal thorns; B, 
pseudospikelet; C, thick-walled culm with a major branch. 



90 



BURGER: FLORA COSTARICENSIS 91 

pseudopetioles less than 1 mm. long, hispidulous with erect hairs on the lower surface, 
these hairs continued onto the midrib of the blade; blades flat, ovate 10-17:1, acuminate, 
3-14 cm. long, 4-10 mm. wide. Inflorescences solitary at the tips of minor, leaf-bearing 
branchlets, each consisting of 1 or 2 pseudospikelets, the base sometimes included in the 
ultimate leaf sheath; pseudospikelets 2-3.5 cm. long, the basal 1 or 2 bracts glumelike, 
shorter than the florets, with a reduced axillary prophyllum and a bud or axillary 
spikelet; remainder of the pseudospikelet consisting of up to 12 normal florets; rachilla 
disarticulating between florets; lemmas 6-7 mm. long, usually 11-nerved, broadly ovate, 
mucronate; palea at least three-fourths as long as its lemma, broadly winged, multi- 
nerved, ciliate on the keels; lodicules 3, flat, ovate, vasculated, ciliolate at the tip; 
anthers 3, ca. 4 mm. long, yellow; ovary swollen and hardened, style 1, stigmas 3; 
caryopsis tan, obovate, 3:1, 4.0-4.5 mm. long, the embryo ca. one-fourth as long, the 
style base persistent. 

This species is common on low elevation savannas in Guanacaste. 
Since the lower parts of the culms are often solid, it may be mis- 
identified as a species ofChitsqiiea, but can usually be differentiated by 
the thorns. The smaller lateral branches of the culms seem to be regu- 
larly hollow. We have collections from N of Bagaces, 10 km. S of La 
Cruz, and Hacienda Murcielago. The only flowering colony seen was on 
the road to Hacienda los Inocentes, 3 km. E of the CIA. At this site, 
and also further east on the same road, a large colony was in flowering 
or fruiting condition in 1976. The plants were all dying. An im- 
mediately adjacent colony, with slightly different foliage, was com- 
pletely vegetative. Fruiting specimens from this colony are Pohl & 
Pinette 12329 (ISC, US, F, CR). 

Bambusa vulgaris Schrad. ex Wendl., Coll. PI. 2:26, p. 47. 1810. 
Figure 27. 

Clumps large, open, the culms erect to arching, 10-15 m. long; internodes cylindrical, 
up to 10 cm. thick, rather thin-walled, yellow or striped with yellow and green; nodes not 
prominent, usually brown-ciliate; sheaths of main culms 15-25 cm. long, 18-23 cm. wide, 
appressed-hispid above with brown hairs; sheath blades triangular, acute, 5-15 cm. long, 
up to 10 cm. wide, appressed pubescent on both inner and outer surfaces; auricles 
rounded, bristly-ciliate; ligule 5-8 mm. long; sheaths of foliage leaves pubescent, their 
rounded auricles bearing a few bristles; ligule short, ciliolate; leaf blades flat, 15-25 cm. 
long, 18-43 mm. wide, their surfaces usually glabrous when mature; edges and marginal 
nerves scabrous; pseudopetiole ca. 5 mm. long. Inflorescence large, leafy, compound, the 
spikelike branches with fascicled clusters of pseudospikelets at the nodes; pseudo- 
spikelets ca. 2 cm. long, subtended by short ciliate prophylls and basal bracts (glumes?) 
that subtend lateral spikelets, the rachilla continuing into a true spikelet, without evi- 
dent glumes; florets 6-10, some of them sterile; lemmas many-nerved, ca. 10 mm. long, 
broadly ovate, acute, the upper margins ciliate; palea about as long as the lemma, 
narrowly oblong, pectinate-ciliate, the hairs longest near the tip; rachilla segments 
clavate; lodicules 3, oblong, long-ciliate toward the tip; anthers 6, ca. 5 mm. long; style 
elongate, ciliate to the base; stigmas 2-3. The margins of the lemmas are somewhat 
inrolled, so that the spikelet appears to have a deep groove along the center. The above 




FIG. 27. Bambusa vulgaris. A, pseudospikelet containing several spikelets; B, 
foliage-bearing vegetative branchlet; C, portion of inflorescence with pseudospikelets. 



BURGER: FLORA COSTARICENSIS 93 

description was compiled from that of Gamble and limited spikelet material available to 
me. 

This species is frequently cultivated in Central America for orna- 
ment and construction materials. We have seen no blooming Central 
American specimens in the field or herbarium, and literature records 
indicate that blooming is very rare. Nearly all clumps that I have seen 
have yellow and green striped internodes. This form has variously 
been designated as var. striata Gamble or as horticultural form vittata 
A. & C. Riv. The native home of this Old World species is uncertain, 
but it is widely cultivated in both hemispheres. 

BOTHRIOCHLOA 0. Kuntze 

REFERENCES: S. T. Blake, Taxonomic and nomenclatural studies in 
the Gramineae, No. 1, Proc. Roy. Soc. Queensland 80:55-84. 1969. F. 
Gould, New North American Andropogons of subgenus Amphilophis 
and a key to those species occurring in the United States, Madrono 
14:18-29. 1957. 

Caespitose or stoloniferous grasses; inflorescence of several rames borne on a central 
rachis; rames consisting of several to many spikelet pairs borne on a slender rachis that 
disarticulates at the apex of each internode, spikelet pairs falling as units with the 
attached rachis internode. One spikelet of each pair sessile, awned, perfect-flowered and 
one pedicellate, awnless, staminate or sterile; some basal pairs of spikelets alike and 
awnless, staminate or sterile; rachis internodes and pedicels with thickened margins and 
a very thin, translucent line down the middle. Spikelets dorsally compressed, the sessile 
ones with a flattened, many-nerved first glume whose edges are inrolled over the mar- 
gins of the second and slightly keeled on the upper half; second glume slightly longer 
than the first, acuminate, 3-nerved, convex on the back; glumes completely enclosing 
and concealing the floret. Awned spikelets: florets 2, the lower represented by a thin, 
nearly nerveless translucent scale, the second reduced to the flattened base of the awn; 
lodicules 2, truncate; awn twisted and geniculate. Pedicellate spikelets: dorsally flat- 
tened, biconvex, similar to the sessile spikelets but awnless; a single lemma present; no 
flower present. 

Bothriochloa is primarily a genus of the Old World tropics, with a 
few species native in warmer parts of the Americas. It is similar to 
Andropogon, from which it differs in the thin line down the middle of 
the rachis joints and pedicels, and in the fertile lemma, which is re- 
duced to an awn, lacking a membranaceous body. (Panicoideae: An- 
dropogoneae.) 

Bothriochloa pertusa (L.) Camus, Ann. Soc. Linn. Lyon n. ser. 
76:164. 1931. Holcus perticsus L., Mant. PL 2:301. 1771. Andropogon 
pertusus (L.) Willd., Sp. PL 922. 1806. Figure 28. 




FIG. 28. Bothriochloa pertusa. A, inflorescence and culm; B, portion of a rame, the 
sessile spikelets with pits in the first glumes. 



94 



BURGER: FLORA COSTARICENSIS 95 

Plants sprawling, weak-stemmed, rooting at the lower nodes; duration indefinite; 
culms 30-100 cm. long, freely branching, glabrous except upwardly bearded at the 
nodes, hollow; sheaths keeled, more or less hirsute; ligule a ciliate membrane, 0.7-1.2 
mm. long; leaf blades 3-4 mm. wide, with scattered elongate papillose-based hairs on the 
margins and above the ligule. Peduncle exserted up to 12 cm. from the nearly glabrous, 
bladeless, upper sheath, glabrous, slightly bearded at the apex; inflorescences terminal 
on the main culms and on leafy branches, 3-5 cm. long, fan-shaped, often purplish. 
Rames several, racemosely arranged along a short rachis, ascending. Sessile spikelets 
awned, 3.2-4.0 mm. long, lanceolate; first glume ca. 9-nerved, tapering to a narrow 
truncate apex, with a prominent circular pit near the middle; second glume slightly 
longer, tapering to an acuminate apex, its margins somewhat ciliate above; lower lemma 
oblong, 2.5-2.7 mm. long; upper lemma reduced to the awn, which has a flattened whitish 
base; anthers 3, yellow, 1.0-1.8 mm. long. Chromosome numbern = 20 from this speci- 
men. 

Weed; dock area, Quepos. January. 

Introduced from the Old World; southern United States and Mexico; 
West Indies. 



BOUTELOUA Lagasca 

REFERENCES: F. W. Gould, Taxonomy of the Bouteloua repens com- 
plex, Brittonia 21:261-274. 1969. F. W. Gould & Z. J. Kapadia, Biosys- 
tematic studies in the Bouteloua curtipendula complex, Brittonia 
16:182-207. 1964. David Griffiths, The grama grasses: Bouteloua and 
related genera, Contr. U.S. Natl. Herb. 14:343-428 + XI. 1912. 

Annual or perennial caespitose or rhizomatous grasses; inflorescence a raceme of 
1-many unilateral spikes; spikelets usually 3-many per spike, borne in 2 rows on the 
lower side of the rachis, usually densely crowded; disarticulation above the glumes or (in 
all our species) at the base of the individual spikes, which fall as units; glumes 1-nerved, 
unequal, shorter than the florets; spikelets with one fertile floret at the base and one or 
two variously modified or ornamented sterile florets above it; lemma 3-nerved, the 
nerves often excurrent as awns. 

Bouteloua is an American genus of about 40 species, native to warm 
or arid portions of North, Central, and South America. In the Central 
American flora, its closest relatives are Pentarraphis, Aegopogon, 
Chloris, Eustachys, and Gymnopogon. (Chloridoideae: Chlorideae.) 

KEY TO SPECIES OF Bouteloua 

la. Spikes 20 or more per inflorescence, drooping 2 

Ib. Spikes 10 or fewer per inflorescence, usually ascending or erect 3 

2a. Spikelets 2-4 per spike; anthers ca. 1.5 mm. long; weak prostrate annual 

B. disticha 

2b. Spikelets 8-11 per spike; anthers ca. 3 mm. long; tall erect perennial B. media 
3a. Rachis and glumes heavily bearded; awns short and inconspicuous 

B. chondrosioides 



96 FIELDIANA: BOTANY 

3b. Rachis and glumes glabrous or short ciliate; awns usually conspicuous 4 

4a. Spikes slender, successive spikelets separated by about half their length; 
rudimentary floret sterile, reduced to 3 stiff awns attached to a small rigid 

cylindrical lemma body B. americana 

4b. Spikes not slender, the spikelets crowded; rudimentary floret with a well de- 
veloped flat lemma 5 

5a. Awns of rudimentary floret 12-17 mm. long; spikelets 3-4 per spike, crowded near 

the base of the rachis; plants annual B. alamosana 

5b. Awns of rudimentary floret 2-10 mm. long; spikelets 4-8 per spike, distributed along 
the lower half of the rachis; plants perennial B. repens 

Bouteloua alamosana Vasey, Contr. U.S. Natl. Herb. 1:115. 1891. 
Figure 29. 

Weak, sprawling annual; culms 20-80 cm. long, branching freely from the base and the 
lower culm nodes, ca. 1 mm. thick, solid and pithy, glabrous; sheaths shorter than the 
internodes, glabrous to papillose-hirsute; ligule a minute membranous rim, ciliolate, 
0.2-0.3 mm. long; blades 3-7 cm. long, 1.5-3.0 mm. wide, more or less papillose-hirsute on 
both surfaces, especially near the base; peduncle 3-25 cm. long; inflorescences terminal 
and axillary; inflorescence a unilateral raceme of 4-9 ascending or spreading unilateral 
spikes; rachis of spikes strongly hispid-bearded, flat, ca. 10 mm. long, prolonged as a 
thickish stipe ca. 1 mm. long below the spikelets. Spikelets usually 3-4, crowded near the 
base of the rachis, ca. 8 mm. long (excluding the awns), often purplish; glumes subequal, 
5-7 mm. long, 1-nerved, linear to lanceolate, strongly short-hispid on the keels; lower 
floret 6.0-6.5 mm. long; lemma glabrous, lanceolate, the 3 nerves extending as short 
awns from the upper quarter of the body; palea 7-8 mm. long, longer than the lemma, 
firm, oblong, bidentate, pubescent between the keels, the margins broad, overlapping 
near the apex; anthers 1.1-1.3 mm. long; second floret staminate; lemma 5.5-6.0 mm. 
long, wider than the first lemma; awns subequal, 12-17 mm. long, flat, rigid, scabrous, 
the lateral ones arising about the middle of the lemma, the middle one between 2 apical 
teeth; palea ca. 5.5 mm., bidentate. Chromosome number n = 30 from a Honduran 
specimen. 

This species has been found only near Liberia, along the Carretera 
Interamericana, at Puntarenas, and on the bluffs at Playas del Coco. 
Blooming in November and December; elevations from sea level to 100 
m. Mexico to northern Guanacaste, along the Pacific slope. 

Bouteloua americana (L.) Scribn., Proc. Acad. Nat. Sci. Philadel- 
phia 43:306. 1891. Aristida americana L., Syst. Nat. ed. 10; 2:879. 
1759. Figure 30. 

Duration indefinite; culms prostrate to ascending, usually 25-50 (100) cm. long, freely 
branching; prophyllum 25-35 mm. long, bidentate at tip; culms 1.0-1.5 mm. thick, solid, 
pithy, glabrous; leaves numerous, the sheaths shorter than the internodes, glabrous; 
ligule 0.5-0.8 mm. long, a strongly ciliate membrane; leaf blades 4-11 cm. long, 2-4 mm. 
wide, pustulose-ciliate on the margins near the base and sometimes on the upper sur- 
face. Peduncle usually 3-5 cm. long; inflorescence 6-12 cm. long, of 5-9 slender, ascending 
unilateral spikes borne racemosely along a slender rachis, naked at the base for 1-2 mm., 
the rachis 2-4 cm. long, triquetrous, the 5-10 spikelets somewhat remote, appressed, 




FIG 29. Bouteloua species. B. repens: A, inflorescence; B, single spike, seen from 
beneath; B. alamosana: C, single spike. 



97 



FIG. 30. Bouteloua species. A, B. media; B, B. chondrosioides, C, B. americana. 

98 



BURGER: FLORA COSTARICENSIS 99 

distant by one-half to three-fourths of their length, 5.5-8.0 mm. long, excluding the awn 
of the rudiment; disarticulation at the base of the individual spike, or sometimes above 
the glumes, the 2 florets falling together; glumes subequal, 3.5-4.5 mm. long, 1-nerved, 
narrowly ovate, acute; florets 2, the lower lemma with an oblique bearded callus, other- 
wise glabrous, lanceolate, 3-nerved, the nerves excurrent as short awns, the central one 
ca. 2 mm. long; lemma and palea firm, shining, purplish; palea bidentate at the tip; 
rachilla segment slender; rudimentary floret reduced to 3 stiff flat scabrid awns jointed 
onto a very short firm cylindrical lemma body; palea ca. 1.0-1.5 mm. long; rachilla 
prolonged beyond the palea as a minute bristle. Chromosome number n = 20 from Costa 
Rican specimens. 

This species has been collected in Costa Rica only in the vicinity of 
Puntarenas, from sea level to 125 m. elevation. It grows along the 
Carretera Interamericana south of the Puntarenas junction. October. 
Bahamas and Caribbean Islands; Guatemala to Panama, Venezuela, 
and Brazil. 

Bouteloua chondrosioides (H.B.K.) Benth. ex S. Wats., Proc. 
Amer. Acad. Sci. 18:179. 1883. Dinebra chondrosioides H.B.K., Nov. 
Gen. & Sp. 1:173. 1816. Figure 30. 

Erect caespitose perennial; culm 10-50 cm. tall, ca. 1 mm. thick, ridged, glabrous, 
solid, pithy, arising from a knotty crown; nodes glabrous; foliage mostly aggregated on 
the lower half of the culm; sheaths shorter than the internodes, glabrous, glaucous, 
ridged, 1-10 cm. long, the upper ones much reduced, 1.5-3.0 mm. wide, somewhat 
pustulose-hispid, especially on the margins; peduncle exserted 2-7 cm.; inflorescence 3-7 
cm. long, a raceme of 3-8 ascending or appressed thick, rhombic spikes; individual spikes 
8-10 mm. long, purplish, heavily bearded at the base and along the rachis; spikelets 9-11 
per spike, densely crowded; rachis usually extended as a naked point up to 5 mm. beyond 
the spikelets. Spikelets 7.0-7.5 mm. long; first glume acicular, 2.5-4.5 mm. long, hispid 
along the midrib; second glume 4.5-6.5 mm. long, narrowly lanceolate, with a very 
broad, flat midrib which is heavily hispid; lower lemma 4.7-6.2 mm. long, narrowly 
ovate, hispid on the upper half, especially along the nerves; awns 3, short, at the tip of 
the lemma; palea longer than the lemma, 5.0-7.2 mm. long, somewhat hispid on the 
upper half; anthers yellow, 2.8-3.5 mm. long; second floret rudimentary, composed of 3 
awns 2-7 mm. long, the central one sometimes with a membranaceous margin. Chromo- 
some numbers n = 10, 20. 

Western Texas and southern Arizona to Guanacaste. Reported from 
the Nicoya Peninsula by Hitchcock. 

Bouteloua disticha (H.B.K.) Benth., J. Linn. Soc. Bot. 19:105. 
1881. Polydon distichum H.B.K., Nov. Gen. & Sp. 1:175. 1816. 
Bouteloua pilosa (Hook, f.) Benth. ex S. Wats., Proc. Amer. Acad. 
Sci. 18:179. 1883. 

Annual; plants decumbent to prostrate, the culms rooting at the lower nodes; branch- 
ing abundant; prophyllum 15-35 mm. long, the keels ciliolate; culms glabrous, ca. 1 mm. 
thick, solid, pithy; sheaths much shorter than the elongated internodes, glabrous to 
papillose-hirsute; dewlap prominent; auricular hairs sometimes present; ligule a ciliolate 



100 FIELDIANA: BOTANY 

membrane, 0.2-0.5 mm. long; leaf blades 6-13 cm. long, 2-5 mm. wide, glabrous to 
papillose-hirsute on both surfaces and the margins; peduncle slender, glabrous, exserted 
4-22 cm.; inflorescence solitary, terminal, unilateral, 8-15 cm. long, bearing 30-50 pen- 
dant spikes on minute branchlets; individual spikes unilateral, the 2-4 spikelets borne on 
the underside of the stiff flattened rachis near its base, occasionally 1 or 2 of them 
reduced or sterile; rachis of spikes 4.0-5.5 mm. long, often bidentate at the tip. Spikelets 
narrow, 5.5-7.5 mm. long, excluding the awn of the rudiment; first glume acicular, 
1-nerved, 3.8-5.5 mm. long; second glume lanceolate, 1-nerved, 5.5-7.0 mm. long; lemma 
of lower floret glabrous, lanceolate, 5-7 mm. long, the apex trifid, with 3 short awns; 
palea bifid, 5-6 mm. long, glabrous; anthers ca. 1.5 mm. long, orange, second floret 
sterile, with a very short palea, the lemma from very small to larger than the fertile 
floret, deeply 3-lobed, the lateral nerves extending into awns 4-8 mm. long, the midrib 
extending into an awn 7-10 mm. long, arising between 2 hyaline teeth; rachilla not 
prolonged beyond the second floret. Chromosome number n = 20 from Costa Rican 
specimens. 

Roadsides and weedy open areas, sea level to 1,200 m. elevation; 
Pacific slope, from northern Guanacaste to Atenas. October to Feb- 
ruary. Southern Mexico to Ecuador, Peru, and the Galapagos Islands. 

Bouteloua media (Fourn.) Gould & Kapadia, Brittonia 16:196. 1964. 
Atheropogon medius Fourn., Mex. PI. 2:139. 1881. Figure 30. 

Tall, leafy perennial, in dense clumps; culms erect, 70-200 cm. tall, usually unbranched 
or sometimes with an axillary inflorescence below the terminal one; culms solid, pithy, 
scabrid or papillose-hirsute; sheaths mostly overlapping, scabrous, sometimes 
papillose-hirsute; ligule membranaceous, ciliolate, 0.5-0.7 mm. long; leaf blades up to 30 
cm. or more long, 4-6 mm. wide, scabrous, also papillose-hirsute on auricles, upper 
surface above the base, and margins; peduncle scabrous, ridged; terminal inflorescence a 
slender raceme 20-25 cm. long, of up to 40 drooping unilateral spikes borne on slender, 
lax, scabrous branchlets 2-3 mm. long; individual spikes 1-2 cm. long, tending to be 
approximate in pairs. Spikelets usually 8-11 per spike, often some of the basal ones 
abortive, sessile in 2 rows on the lower side of the flat scabrous rachis; rachis 8-10 mm. 
long, sometimes extended beyond the spikelets as a naked point. Spikelets 5-6 mm. long, 
excluding the awns; first glume 4.0-4.5 mm. long, linear, awn-tipped, second glume 
4.8-5.3 mm. long, lanceolate, acute; lemma of lower floret 5.0-5.5 mm. long, lanceolate, 
scabrid in lines, the nerves extended into 3 short awns near the tip; palea 5.2-5.5 mm. 
long; anthers 2.8-3.5 mm. long, yellow to orange; rudimentary florets 1 or 2, the first 
with a lemma ca. 3 mm. long, bifid to the base, the lateral awns 4-5 mm. long, the central 
one 5-9 mm. long, palea absent; second rudimentary floret, when present, much smaller. 
Our single chromosome count of this species was aneuploid, with 2n = 27. The only 
previous count was diploid, 2n = 20. 

Upper grassy slopes of bluffs, south end of Play as del Coco, 
Guanacaste; elevation ca. 100 m. July to December. This is the south- 
ern limit of the range of this species, which extends southward from 
southern Mexico. 

Bouteloua repens (H.B.K.) Scribn. & Merr., Bull. U.S.D.A. Div. 
Agrost. 24:26. 1901. Dinebra repens H.B.K., Nov. Gen. & Sp. 1:172. 



BURGER: FLORA COSTARICENSIS 101 

1816. B(wtelouafiliformis (Fourn.) Griffiths, Contr. U.S. Natl. Herb. 
14:413. 1912. B. pubescens Pilger, Verb. Bot. Vereins Prov. Branden- 
burg 51:193. 1909. B. heterostega (Trin.) Griffiths, Contr. U.S. Natl. 
Herb. 14:414. 1912. Figure 29. 

Perennial; culms 15-65 cm. long, glabrous, solid, pithy, prostrate to ascending, the 
lower nodes sometimes rooting; sheaths glabrous to softly pubescent; auricular hairs 
present; ligule a minute ciliolate rim, 0.2-0.3 mm. long; blades 5-20 cm. long, 1-4 mm. 
wide, papillose-ciliate along the margins near the base, sometimes puberulent or pubes- 
cent on one or both surfaces; peduncle stiff, 4-10 cm. long; inflorescence 4-14 cm. long, a 
unilateral raceme of usually 7-9 unilateral spikes, these deciduous as wholes; individual 
spikes with a minute ciliate stipe at the base, bearing usually 4-8 spikelets crowded in 2 
rows on the basal 6-10 mm. of the rachis, which extends above the spikelets as a naked 
stipe 4-6 mm. long. First glume 4-6 mm. long, 1-nerved, ovate, scabrous on the keel; 
second glume similar, 4-9 mm. long; lemma of lower floret 5.0-7.5 mm. long, lanceolate, 
glabrous; lateral nerves excurrent as short awns ca. 1 mm. long near the tip, the central 
awn slightly longer; palea 6-8 mm. long, glabrous or cottony between the keels; anthers 
3.5-5.5 mm. long, yellow or orange, second floret usually staminate, its lemma 5.5-7.0 
mm. long, ovate, 3-awned, the lateral nerves excurrent as awns about halfway up the 
lemma, the midnerve awned between 2 teeth; awns about equal, 2-10 mm. long; anthers 
usually present, smaller than those of the lower floret; palea 4-7 mm. long, glabrous or 
cottony between the keels; rachilla prolonged beyond the second floret as a short bristle. 
Chromosome numbers n = 10, 20, 30, 21, 22, ca. 45, 46. 

Savannas, roadsides, often on volcanic ash; from sea level to 100 m. 
Guanacaste, S to the area of Puntarenas. July to December. Southern 
Arizona and Texas to Venezuela and Colombia; Caribbean Islands. 



BRACHIARIA Grisebach 

REFERENCE: S. T. Blake, New criteria for distinguishing genera 
allied to Panicum (Gramineae), Proc. Roy. Soc. Queensland 70:15-19. 
1958. 

Plants annual or perennial, the culms often decumbent and rooting. Inflorescence a 
panicle of several-many slender racemes borne racemosely along a central rachis; 
racemes rarely secondarily branched and bearing short fascicles of spikelets; spikelets 
usually solitary or paired, short-pedicellate along the rachis, their first glumes turned 
toward the midrib of the rachis. Spikelets disarticulating below the glumes, dorsally 
compressed, ovate-obovate, plano-convex or biconvex; first glume short, 1-many- 
nerved; second glume and lower (sterile) lemma subequal, as long as the spikelet, 5-9- 
nerved; lower lemma with a well-developed palea and usually a staminate flower; upper 
(fertile) floret shorter than the second glume and sterile lemma, cartilaginous or rigid, 
rugulose or striate, the lemma elliptical or obovate, its margins incurved over the keels 
of the equal palea of similar texture; palea sometimes convex; lodicules 2, truncate; 
stamens 3; style branches separate; caryopsis elliptical, dorsally flattened, with a large 
embryo. 

Brachiaria is a large genus of grasses of warm climates in both the 
eastern and western hemispheres, most numerous in Africa. It is most 



102 FIELDIANA: BOTANY 

closely related to Eriochloa, Setaria, Paspalidium, and Urochloa. It 
is distinguished mostly by the simple panicle branches with the 
spikelets usually in orderly rows along them, the first glumes turned 
toward the midrib. Blake has indicated that the presence of a promi- 
nent "rupture line" at the base of the fertile lemma distinguishes this 
genus from Panicum, although this feature occurs throughout the 
Paniceae. (Panicoideae: Paniceae.) 

KEY TO SPECIES OF Brachiaria 

la. Spikelets 4.5 mm. or more long 2 

Ib. Spikelets 4.0 mm. or less long 3 

2a. Rachis of racemes prominently papillose-ciliate; spikelets hairy near the tip 

B. brizantha 

2b. Rachis of racemes not ciliate; spikelets glabrous B. plantaginea 

3a. Spikelets pubescent with papillose-based hairs B. mollis 

3b. Spikelets glabrous 4 

4a. Spikelets 3 mm. or less long, dull yellow, brown, or deep purple; racemes 

numerous B. fasciculate 

4b. Spikelets over 3.2 mm. long, green or marked with purple; racemes few to 

many 5 

5a. First glume 9-nerved; nodes glabrous or nearly so; racemes 3-4 B. distachya 

5b. First glume 1-nerved; nodes conspicuously retrorsely hirsute; racemes 
numerous B. mutica 

Brachiaria brizantha (Hochst.) Stapf, Fl. Trop. Africa 9:531. 1919. 
Panicum brizanthum Hochst. ex Rich., Tent. Fl. Abyss. 2:363. 1851. 

Erect perennial, to 2 m. tall; culms branching occasionally from the middle nodes, 
internodes up to 3 mm. thick, hollow, thick-walled, smooth and glabrous or somewhat 
hairy; sheaths about equal to the internodes, glabrous; ligule a short, stiffly ciliate 
membrane, in total 1.2-2.0 mm. long; leaf blades 15-35 cm. long, 7-18 mm. wide, glabrous 
or pubescent, the margins scabrous, with thick, whitish sclerenchyma bands. Inflores- 
cence of 2-many remote arching racemes, these one-sided, 6-12 cm. long, slender, the 
spikelets apparently 1-rowed; rachis flat, less than 1 mm. wide, papillose-ciliate on the 
edges. Spikelets 5.0-5.8 mm. long, obovate 2.5:1, with a short basal stipe ca. 0.5 mm. 
long, a similar internode between the first and second glumes; first glume broadly deltoid 
with overlapping edges, 7-9-nerved; second glume and lower (sterile) lemma equal, 
about as long as the spikelet; second glume 5-7-nerved; lower lemma 5-nerved, with a 
large palea and sometimes 3 stamens; both second glume and lower lemma sparsely 
papillose-hirsute near the tip and sometimes purple-marked; upper floret 4.3-4.6 mm. 
long, rigid, finely striate or minutely rugulose; palea equal to the lemma; lodicules 2, 
truncate; anthers 3, 2.7 mm. long, brown; styles separate; stigmas purple. 

Cultivated in the grass garden at the CATIE at Turrialba and at 
Guapiles; possibly in commercial production. Native to tropical Africa. 

Brachiaria distachya (L.) Stapf, Fl. Trop. Africa 565. 1919. 
Panicum distachyon L., Mant. Alt. 183. 1771. Panicum subquad- 



BURGER: FLORA COSTARICENSIS 103 

riparum Trin., Gram. Pan. 145. 1826; Brachiaria subqitadripara 
(Trin.) Hitchc., Lingnan Sci. J. 7:214. 1931. Figure 32. 

Duration indefinite; plants sprawling, the culm bases long decumbent and rooting at 
the nodes, the erect portions 20-30 cm. long; branching abundant, older culms bearing 
fascicles of branches; culms solid, glabrous, or with scattered papillose-hispid hairs; 
nodes glabrous or bearded below the sheath margin; sheaths keeled, glabrous or with 
scattered hispid hairs, the overlapping margin densely papillose-ciliate; ligule a short 
membrane, long-ciliate, in total 0.5-1.3 mm. long; leaf blades flat, 3-9 cm. long, 4-8 mm. 
wide, the edges thickened, scabrous, glabrous or with scattered papillose-hispid hairs on 
the basal margins and on the surfaces. Peduncle included or exserted up to 15 cm.; 
inflorescences numerous, terminal or axillary, 4-8 cm. long, composed of usually 3 short, 
ascending, racemosely arranged, one-sided racemes, each 1.5-3.5 cm. long. Spikelets 
borne in 2 rows on the lower side of a winged, triquetrous rachis ca. 1 mm. wide; pedicels 
0.5-0.7 mm. long, angular. Spikelets glabrous, 3.5-3.8 mm. long, ovate to obovate, first 
glume 1.6-1.8 mm. long, 9-nerved, transversely depressed ovate, blunt, enwrapping the 
base of the spikelet, the margins meeting; second glume and lower (sterile) lemma equal, 
as long as the spikelet; second glume 7-nerved; sterile lemma 5-nerved, inclosing an 
oblong palea 2.7-2.8 mm. long; upper (fertile) lemma rigid, elliptic-obovate 2:1, 2.7-2.8 
mm. long, rugulose, with an areole near the base; margins thick, barely covering the 
keels of the palea of similar texture and length; anthers 1.3 mm. long; stigmas purple; 
caryopsis elliptical 2:1, 2.0-2.1 mm. long, whitish; embryo large. Chromosome number 
n = 36. 

Elsewhere in America, it is known only from Veracruz and Pro- 
greso, Mexico. Pacific Islands and southeastern Asia; tropical Africa. 
Known in Costa Rica only by the following specimen: Puntarenas, 
Esterillos Este, sandy field behind beach, P. & D. 11687, 28 January 
1969. 

Brachiaria fasciculata (Sw.) Parodi, Darwiniana 15:96. 1969. 
Panicum fasciculatum Swartz, Prodr. Veg. Ind. Occ. 22. 1788. 

Annual; plants tufted, erect, or the lower nodes of the culms decumbent and rooting; 
culms 10-100 cm. long, branching from the lower and middle nodes; prophylla prominent, 
up to 5.5 cm. long; internodes up to 2 mm. thick, hollow, thick-walled, more or less 
papillose-hispid, especially toward the apex; sheaths about as long as the internodes, 
keeled near the apex, more or less papillose-hispid, the overlapping margin strongly 
papillose-ciliate; ligule a short membrane, densely ciliate, in total 0.3-2.3 mm. long; leaf 
blades flat, rounded to the base, 4-30 cm. long, 7-18 mm. wide, more or less papillose- 
pilose or hispid on both surfaces. Inflorescences terminal on the culm or on leafy 
branches; peduncle exserted up to 15 cm.; panicles 3.5-15 cm. long, ovoid, 1-9 cm. wide, 
composed of numerous ascending simple branches racemosely arranged along a grooved 
central rachis, 1-several per node; spikelets solitary, short-pedicellate in 2 rows along 
the lower sides of the branches, or more commonly in small clusters of 2-5 borne along 
the lower sides of the primary branches; rachis and branches angular, scabrous, some- 
times papillose-pilose. Spikelets turgid, biconvex, obovate 5:3, bluntly mucronate, dull 
yellow or deep purple, 2.3-3.0 mm. long; first glume transversely ovate, acute, its edges 
overlapping; nerves 3-5; second glume and lower (sterile) lemma equal, as long as the 



104 FIELDIANA: BOTANY 

spikelet; second glume 9-nerved, often with small cross-veins near the apex; lower 
lemma similar, 7-nerved; upper (fertile) floret 1.9-2.5 mm. long, elliptical-obovate, acute 
4:3; lemma rigid, strongly rugose, with a conspicuous basal areole; margins thick, clasp- 
ing the keels of the similar convex palea of equal length. Chromosome number n = 9 
from Costa Rican specimens. 

Open disturbed areas, pastures, roadsides, river banks; low eleva- 
tions on the Pacific slope; common in Guanacaste, usually below 600 m. 
elevation; western parts of the Meseta Central; Turrialba; Limon area; 
Guapiles. Blooming June to February. Extreme southern United 
States to Brazil and Ecuador; West Indies. 

This species has been included in the genus Panicum in most Ameri- 
can publications. Recent authors have assigned it to Brachiaria, al- 
though the placement of the spikelets is not as regular as in other 
species. The current placement is based principally on the rugose 
character of the fertile lemma and the presence of an areole (germina- 
tion lid) at its base, along with the rather simple panicle branches. 

Brachiaria mollis (Sw.) Parodi, Darwiniana 15:100. 1969. Panicum 
molle Swartz, Prodr. Veg. Ind. Occ. 22. 1788. 

Annual; plants erect to sprawling, the bases sometimes long decumbent and rooting at 
the nodes; branching from the lower and middle nodes; prophylla up to 2.5 cm. long; culm 
internodes up to 2.5 mm. thick, hollow, thick-walled, more or less papillose-pilose or 
puberulent; nodes bearded; leaf sheaths about as long as the internodes, papillose-pilose 
or puberulent; ligule a ciliate membrane, 0.5-1.0 mm. long; leaf blades broad-based, 6-14 
cm. long, 5-15 mm. wide, flat, papillose-pilose, or velvety. Peduncle included or exserted 
up to 13 cm; inflorescences terminal on leafy branches, numerous, 3-7 cm. long, 1-3 cm. 
wide, consisting of up to 8 short, ascending, 1-sided racemes, each 1-3 cm. long; rachis 
and branches puberulent or pilose, the short pedicels sometimes bearing glassy hispid 
hairs; spikelets solitary or paired along the lower sides of the rachis, the first glumes 
turned toward the center of the rachis. Spikelets 3.4-4.0 mm. long, villous, obovate 2:1, 
apiculate, biconvex; first glume 2.0-2.7 mm. long, 5-nerved, ovate, acute; second glume 
and lower (sterile) lemma equal, as long as the spikelet; second glume 7-nerved; lower 
lemma similar, but 5-nerved; its palea 2.7-3.0 mm. long; upper (fertile) floret 2.6-3. 1 mm. 
long, rigid, obovate 5:3, rugulose, apiculate, its margins inrolled over the margins of a 
similar palea; lodicules 2, fleshy, truncate; anthers 3, tan, 1.0-1.1 mm. long; styles 
separate; stigmas purple; caryopsis white, 2 mm. long, elliptical 4:3; embryo three- 
fourths as long as the grain. Chromosome number n = 27 from Costa Rican specimens. 

Occasional, dry roadsides and savannas, low elevations, northern 
Guanacaste; Puntarenas, Atenas. June to November. Mexico and the 
West Indies to Argentina. 

This species has generally been included in the genus Panicum in 
American publications, but has been transferred to Brachiaria be- 
cause of the form of the inflorescence and the rugose floret. 



BURGER: FLORA COSTARICENSIS 105 

Brachiaria mutica (Forsk.) Stapf, Fl. Trop. Africa 9:526. 1919. 
Panicum muticum Forsk., Fl. Aegypt.-Arab. 20. 1775. Panicum 
purpurascens Raddi, Agrost. Bras. 47. 1823. Figure 31. 

Sprawling perennial, the culms becoming long-decumbent and rooting at the lower 
nodes, up to 6 m. long, branching from lower and middle nodes; internodes glabrous, 
hollow, thick-walled; nodes prominent, retrorsely papillose-hirsute; sheaths longer than 
the internodes, more or less papillose-hirsute to nearly glabrous; ligule a very short 
membrane, densely white ciliate, in total 1.5-1.8 mm. long; dewlap and collar finely 
velvety; blades flat, up to 25 cm. long and 15 mm. wide, mostly glabrous or with a few 
hairs near the base; midrib broad and white above near the base; margins thick, purple, 
scabrous. Inflorescences terminal on leafy branches, up to 20 cm. long, of several to 
many solitary or clustered ascending racemes borne along a central rachis; racemes 1-7 
cm. long; spikelets solitary, paired, or in small clusters along the lower sides of the 
triquetrous rachis; bases of branches velvety; rachis up to 1 mm. wide, the angles 
scabrous and bearing scattered papillose hairs. Spikelets 3.2-3.4 mm. long, ovate 3:2, 
acute, often purple, glabrous; first glume 0.8-1.2 mm. long, deltoid, 1-nerved; second 
glume and lower lemma equal, about as long as the spikelet; second glume 5-7-nerved; 
lower lemma similar, 5-nerved, inclosing a large palea that frequently protrudes be- 
tween the lemma and second glume at the tip; stamens 3; upper (fertile) floret 2.1-2.5 
mm. long, elliptic-obovate, striate or rugulose; palea similar, flat; lodicules 2, truncate; 
anthers 3, 1.3-1.5 mm. long, yellow or purple; style branches separate; stigmas purple. 

Cultivated for forage, especially on the Caribbean slope and occur- 
ring in the wild, in wet sites or water; elevations up to 1,600 m. This 
species has had an involved nomenclatural and migrational history. It 
has been known as Panicum purpurascens in American literature, but 
is now usually referred to the genus Brachiaria. It is probably of 
African ancestry, but has long been resident in the American tropics. 
The plants are very similar to those of Eriochloa polystachya in veg- 
etative and flowering structure and may grow intermixed with the 
latter. Common name: Zacate pard. 

Brachiaria plantaginea (Link) Hitchc., Contr. U.S. Natl. Herb. 
12:212. 1909. Panicum plantagineum Link, Hort. Berol. 1:206. 1827. 
Figure 32. 

Duration indefinite; plants sprawling, the culms decumbent and rooting at the lower 
nodes, branching freely from the prostrate portions, up to 1 m. long; culms glabrous, 
solid or the decumbent parts with a small lumen; nodes glabrous, not prominent; leaf 
sheaths about as long as the internodes, keeled, glabrous but papillose-ciliate on the 
overlapping edge; ligule a very short membrane, ciliate with a dense row of stiff hairs, in 
total 0.5-1.5 mm. long; leaf blades flat, glabrous except for a few long cilia at the base, 
4-21 cm. long, 6-13 mm. wide, the margins thickened, scabrous; midrib prominent be- 
neath. Inflorescences terminal on leafy ascending branches; peduncle included or ex- 
serted up to 8 cm.; inflorescence of 4-5 distant ascending racemes, borne racemosely 
along a flattened, grooved rachis; racemes 2-11 cm. long, slender, bearing spikelets 
nearly to the puberulent basal pulvinus; rachis of racemes prominently 3-winged, 1.1-1.2 




FIG. 31. Brachiaria mutica. Plant, inflorescence, fertile floret, and two views of a 
spikelet. 



106 






FIG. 32. Brachiaria species. B. plantaginea: A, inflorescence; B, C, two views of a 
spikelet; D, rugose fertile lemma; B. distachya: E, inflorescence; F, two views of a 
spikelet; G, fertile lemma. 



107 



108 FIELDIANA: BOTANY 

mm. wide, the angles scabrous; spikelets borne alternately in 2 rows on opposite sides of 
the winged midrib of the rachis, their pedicels up to 1 mm. long; spikelets oriented with 
their first glumes toward the midrib. Spikelets 4.7-5.2 mm. long, ovate-obovate, 2.5-3:1, 
acute, glabrous; first glume transversely broadly ovate, 5:7, blunt, clasping the base of 
the spikelet, the margins in contact with each other, nerves 9-11; second glume and 
lower (sterile) lemma equal, as long as the spikelet, concealing the shorter fertile floret; 
second glume 7-nerved; lower lemma 5-nerved, concealing a membranaceous palea of 
equal length; upper (fertile) lemma 3.2-3.6 mm. long, elliptical 7:4, faintly 5-nerved, 
minutely rugulose, rigid, with a horseshoe-shaped areole near the base; middle of lemma 
flattened or depressed; palea of equal length, its keels and margins covered by the 
inflexed thick margins of the lemma; anthers 3, yellow, 0.7-1.0 mm. long; stigmas purple; 
flowers probably cleistogamous; caryopsis flattened, elliptical, whitish, 2.2 mm. long. 
Chromosome number n = 18 from a Costa Rican specimen. 

Roadsides, cafetales, weedy pastures and savannas, up to 1,500 m. 
elevation; Meseta Central, Cartago, Canas area. Blooming yearlong. 
Mexico to Brazil and Bolivia. 

This species is common around San Jose, and Tonduz noted on a 
herbarium specimen that it was once cultivated in an experimental 
field in Guadelupe. He gives the common name as arrocillo. 

BRACHYPODIUM Beauvois 

Caespitose perennial grasses; culms becoming much-branched; inflorescence a slender 
terminal raceme of a few erect spikelets borne on a slender axis. Spikelets several- 
many-flowered, at first cylindrical, becoming laterally compressed; glumes and lemmas 
rounded on the back, not keeled; glumes somewhat unequal, the first slightly shorter 
than the second, both with about 7 nerves; disarticulation above the glumes and between 
the florets; lemmas 7-nerved, tapering into a short stiff awn; paleas slightly shorter than 
the lemmas, their keels pectinate-ciliate. 

A small genus of about 15 species, mostly of the temperate and 
tropical regions of the eastern hemisphere. Three species have been 
credited to Mexico and Central America, but probably all represent 
phases of one. The genus is easily confused with Agropyron, but 
species of the latter have sessile spikelets and unbranched culms, 
whereas Brachypodium plants have the spikelets borne on short erect 
pedicels, and the plants become much-branched with age. (Pooideae: 
Poeae?) 

Brachypodium mexicanum (Roem. & Schult.) Link, Hort. Berol. 
1:41. 1827. Festuca mexicana Roem. & Schult., Syst. Veg. 2:732. 
1817. Figure 33. 

Perennial, caespitose, becoming bushy-branched, the branches decumbent and root- 
ing from the lower nodes; culms slender, 10-100 cm. long, thin- walled, hollow, glabrous; 
nodes retrorsely silky-bearded; sheaths glabrous, ciliate on the margins, the collar 
pubescent; ligule a ciliate membrane, decurrent on the sheath margin, 1.2-4.0 mm. long; 




J&J 



FIG. 33. Brackypodium mexicanum. A, inflorescence; B, plant base; C, spikelet, 
pedicel, and rachis internode. 



109 



110 FIELDIANA: BOTANY 

blades 4-15 cm. long, 2-6 mm. wide, appressed-hirsute above and beneath. Peduncle 
smooth or scabrous, up to 13 cm. long; racemes terminal on the main culm or on leafy 
branches, linear, 6-11 cm. long, sometimes reduced to 1-2 spikelets, especially when the 
plants are much-branched; spikelets erect, appressed to the rachis segments; pedicels 
villous, stiff, 1.0-2.5 mm. long. Spikelets 15-30 mm. long, readily disarticulating; first 
glume lanceolate, blunt at the tip, stiffish, 7-nerved, 5-10 mm. long; second glume simi- 
lar, 6.5-10.5 mm. long; florets 5-12; lemmas 10-13 mm. long, lanceolate, 7-nerved, scabrid 
on the back, tapering into a short stiff awn 2-6 mm. long; palea 9-10 mm. long, conspicu- 
ously pectinate-ciliate on the keels; anthers 1.5-2.0 mm. long, yellow. Chromosome 
number n = 19 from Costa Rican material. 

Mountains of central and southern Costa Rica; rare; elevations from 
2,000-3,400 m. We have specimens from Irazu, Ascuncion, and Chir- 
ripo Grande. Paramos and open pastures. Blooming probably year- 
long. Mexico, Guatemala, Costa Rica and northern Panama; Colombia 
and Venezuela to Bolivia. 

This species is somewhat variable, especially in awn length and leaf 
blade size. Part of the leaf variation may be attributed to the stage of 
growth and degree of branching of the plants. Fournier, in Mex. PL 
2:125, described two new species of Brachy podium, B. subulatum and 
B. latifolium. Most of the material cited by Fournier for his new 
species and B. mexicanum was collected from the summit of Istepec 
by Liebmann. It seems likely that all are variants of one species. Some 
of our Costa Rican material is a close match for the type of B. sub- 
ulatum Fourn. 

BRIZA Linnaeus 

Caepitose annual grasses; inflorescence a panicle; spikelets several-flowered; glumes 
and lemmas very broad, blunt, placed at right angles to the rachilla; disarticulation 
above the glumes and between the florets; glumes faintly 3-nerved, circular, cucullate; 
lemmas circular, cordate at the base, faintly 5-7-nerved; palea much shorter and nar- 
rower than the lemma. (Pooideae: Poeae.) 

Briza minor L., Sp. PL 70. 1753. Figure 34. 

Caespitose annual; culms erect, simple, 20-50 cm. tall, branching from the base only; 
prophylla prominent at the base of the plant; culms 1-2 mm. thick, hollow, thin-walled, 
glabrous; nodes glabrous, dark, shrunken; leaves 2-4; sheaths glabrous, strongly ribbed, 
shorter than the internodes, the margins united for a short distance above the node; 
ligules membranaceous, the upper ones as much as 8 mm. long, their margins decurrent 
on the sheaths; leaf blades 6-13 cm. long, 4-8 mm. wide, glabrous; peduncle 10-15 cm. 
long, ridged, scaberulous. Panicle solitary, terminal, broadly pyramidal, 10-15 cm. long, 
often nearly as wide; branches solitary or paired, spreading. Spikelets solitary, pendent, 
tremulous on flexuous pedicels, deltoid in outline, broadest at the straight base, about as 
wide as long, 3.0-4.5 mm. long, mostly about 5-flowered; glumes subequal, 1.5-2.0 mm. 
long, faintly 3-nerved, circular but folded into an oblong-cucullate form; lemmas 1.5-2.0 
mm. long, circular and cordate at the base, faintly 5-nerved, utriculate at the center, the 




FIG. 34. Briza minor. Plant, spikelet, and a single floret. 
Ill 



112 FIELDIANA: BOTANY 

paJea closing off the cavity of the lemma; palea obovate, 1.0-1.5 mm. long, ciliate on the 
lateral margins; anthers 3, purplish, 0.7 mm. long. Chromosome number n = 5 from a 
Costa Rican specimen. 

Occasional; roadsides, cultivated fields, pastures, middle elevations, 
from 1,800-2,600 m.; Poas, Barba, Irazu; Cordillera de Talamanca; San 
Jose. Blooming from August to March, possibly yearlong. Introduced 
from Europe; southern United States and Mexico; Guatemala; Costa 
Rica. 

This delicate little grass is quite ornamental and is sometimes culti- 
vated for the odd, trembling spikelets. 

BROMUS Linnaeus 

REFERENCE: T. R. Soderstrom & J. H. Beaman. The genus Bromus 
(Gramineae) in Mexico and Central America, Pub. Mus. Michigan 
State Univ., Biol. Ser. 3(5):465-520. 1968. 

Plants annual or perennial, caespitose or rarely rhizomatous; culms unbranched; 
sheaths with united edges. Inflorescence a solitary terminal panicle. Spikelets several to 
many-flowered, laterally compressed; disarticulation above the glumes and between the 
florets; glumes unequal, acute or acuminate, 1-several-nerved, the second longer and 
usually wider than the first; lemmas 5-9-nerved, rounded or keeled on the back, usually 
awned, the awn arising just below the tip or between 2 apical teeth. 

A large and diverse genus, mostly of temperate climates of the 
northern hemisphere. The spikelets are similar to those of species of 
Festuca, differing in the subapical awns of the lemmas and the usual 
presence of lateral teeth. Vegetatively, Bromus can be separated from 
Festuca by the united margins of the sheaths. (Pooideae: Poeae.) 

KEY TO SPECIES OF Bromus 

la. Second glume 5-nerved; spikelets strongly flattened, glumes and lemmas acutely 
keeled B. carinatus 

Ib. Second glume 3-nerved; spikelets not strongly flattened; lemmas rounded on 
back B. exaltatus 

Bromus carinatus Hook. & Am., Bot. Beechey Voy. 403. 1840. 
Bromus laciniatus Beal, Gr. N. Amer. 2:615. 1896. Figure 35. 

Duration indefinite; plants caespitose, 35-120 cm. tall, erect; culms unbranched, 2-3 
mm. thick, hollow, mostly glabrous, often retrorsely pilose on and below the nodes; 
sheaths mostly longer than the internodes, the lower ones often retrorsely pilose, the 
upper glabrous or nearly so; ligule a thin membrane, 1-3 mm. long; blades flat, 8-33 cm. 
long, 2-7 mm. wide, glabrous or with scattered weak hairs. Peduncle up to 15 cm. long; 
inflorescence a solitary terminal panicle, 15-36 cm. long, open, pyramidal, the lower 
branches up to 15 cm. long, naked below, the spikelets borne near the outer ends. 
Spikelets strongly laterally compressed, 1.5-3.5 cm. long, the glumes and lemmas 





FIG. 35. ZJroratts species. B. exaltatus: A, inflorescence; B, spikelet; B. carinatus: C, 
spikelet. 



113 



114 FIELDIANA: BOTANY 

strongly keeled; first glume 5-10 mm. long, 3-nerved, narrowly ovate; second glume 7-11 
mm. long, 5-7-nerved, lanceolate-ovate; florets usually 6-8; lemmas 8-15 mm. long, 
lanceolate, 7-nerved, glabrous or pubescent on the margins; awn up to 10 mm. long, 
arising between inconspicuous teeth; palea slightly shorter than the lemma; anthers 3, 
yellow. Some plants which are presumably cleistogamous have small anthers, 0.7-1.0 
mm. long, remaining tangled with the stigmas; others have large anthers, 3.5-6.5 mm. 
long. Both types have the same chromosome number and are externally similar. 
Chromosome number n = 28 from two Costa Rican collections. 

Roadsides and pastures, occasional, from 1,700-2,600 m. elevation. 
August and September. Western United States to Costa Rica. 

Bromus catharticus Vahl has been reported from Costa Rica by 
Soderstrom & Beaman (1968). The basis of this report was a specimen 
apparently cultivated in the garden of the National Museum in San 
Jose, and no evidence exists that the species ever became established 
in Costa Rica. This species has recently been passing under the name 
B. unioloides H.B.K. Pinto-Escobar has now shown that the proper 
name is B. catharticus (Caldasia 11:54:9-16). 

Bromus exaltatus Bernh., Linnaea 15:Litt. 90. 1841. Figure 35. 

Perennial; plants 45-80 cm. tall; culms erect from decumbent bases; unbranched; old 
sheaths remaining as fibrous remnants; culms hollow, ca. 2 mm. thick, unbranched, 
glabrous or slightly retrorsely pilose, especially below the nodes; lower sheaths mostly 
longer than the internodes and overlapping, densely retrorsely pilose; upper sheaths less 
pubescent; ligule a brownish membrane, 1-2 mm. long; leaf blades flat, 10-30 cm. long, 
3-7 mm. wide, scabrous on the margins, glabrous beneath, the upper surface with 
scattered weak hairs. Peduncle 10-12 cm. long, glabrous; inflorescence a solitary termi- 
nal panicle, open and nodding, 10-22 cm. long, rather narrow, the branches 1-3 per node, 
few-flowered, rarely up to 11 cm. long; pedicels minutely antrorsely scabrous, short or 
longer than the spikelets. Spikelets laterally compressed, 2.5-3.2 cm. long, usually with 
5-6 florets, the terminal one reduced and sterile; disarticulation above the glumes and 
between florets; first glume linear-lanceolate, acuminate, 1-nerved, 5.0-11.5 mm. long; 
second glume broadly lanceolate, acuminate, 3-nerved, 8.5-14.0 mm. long; florets 12-17 
mm. long, excluding the 2.5-4.0 mm. long awns; lemmas 5-nerved, lanceolate, rounded 
on the back, tapering to the base of the awn, the lateral teeth usually inconspicuous; 
margins, base, and lower part of the back more or less appressed pilose; glumes and 
lemmas often purplish and with golden margins; palea 8.7-10.5 mm. long, narrowly 
elliptical, the keels scabrous, the back sometimes with a few hairs; anthers 3, yellow, 
2.2-2.8 mm. long. Chromosome number n = 1 from a Costa Rican specimen. 

Rare, paramos above 3,200 m. elevation, near Asuncion; Chirripo 
Grande. July to August. Southern Mexico; Guatemala; Costa Rica; 
Volcan Chiriqui in Panama. 

CALAMAGROSTIS Adanson 

Perennial caespitose or rhizomatous grasses; inflorescence a usually narrow or con- 
tracted terminal panicle. Spikelets small, 1-flowered, laterally compressed, the subequal 



BURGER: FLORA COSTARICENSIS 115 

glumes 1- or sometimes 3-nerved, keeled, longer than the floret; disarticulation above 
the glumes; floret 1; lemma 5-nerved, awned from the back or between 2 teeth; callus 
bearded; palea nearly as long as the lemma; rachilla in our species prolonged behind the 
palea as a hairy or naked bristle. 

A large genus of grasses of the temperate and arctic regions, spar- 
ingly represented at high elevations in the tropics. The endosperm in 
some species is pasty, as in Trisetum. (Pooideae: Agrosteae.) 

KEY TO SPECIES OF Calamagrostis 

la. Rachilla internode behind palea glabrous or with few short hairs not exceeding its 

tip; awn inserted near base of lemma C. nuda 

Ib. Rachilla internode heavily bearded, with long hairs extending beyond its tip; awn 

inserted near or above middle of lemma 2 

2a. Culms erect, in dense clumps; leaf blades tightly involute; sheaths auricled; 

anthers 3, 2.5-2.8 mm. long C. intermedia. 

2b. Culms decumbent at base; leaf blades mostly flat, sheaths not auricled; anthers 
2, 1.2-1.4 mm. long C. pittieri 



Calamagrostis intermedia (Presl) Steud., Nom. Bot., ed. 2. 1:250. 
1840. Deyeuxia intermedia Presl, Rel. Haenk. 1:249. 1830. Figure 36. 

Perennial, in dense hard tussocks; plants 45-110 cm. tall, stiffly erect; culms 1.5-3.0 
mm. thick, hollow, glabrous; sheaths mostly basal, densely overlapping; culm leaves 
about 2; sheaths glabrous, the apex on one side prolonged into a stiff rounded auricle, 
1.5-3.5 mm. long, continuous with the ligule; ligule a stiff membrane, 1.0-2.9 mm. long; 
leaf blades mostly from the base of the plants, stiff and rigid, tightly involute, 1.0-1.5 
mm. thick as rolled, 10-45 cm. long, tapering abruptly to a point, scaberulous beneath. 
Peduncle included or exserted up to 20 cm.; inflorescence a solitary terminal panicle, 
purple, 12-35 cm. long, loosely cylindrical, tapering to a narrow apex, the ascending 
lower branches up to 8 cm. long; panicle somewhat interrupted, the scabrous axis and 
branches partially exposed; spikelets appressed along the branches; pedicels slender and 
scabrous, shorter or longer than the spikelets. Spikelets laterally compressed, the 
glumes subequal, keeled, lanceolate-attenuate, 6-8 mm. long exceeding the floret, the 
tips recurved; disarticulation above the glumes; lemma lanceolate, 5.0-6.5 mm. long, the 
callus rather short, sparsely bearded with hairs less than 1 mm. long; back scaberulous; 
nerves faint; apex tapering into 2 teeth about 1 mm. long; awn inserted on the back 
below the middle, geniculate, 7-11 mm. long; palea broad, 4-5 mm. long, the apex 
truncate; anthers 3, yellow or purple, 2.5-2.8 mm. long; rachilla 1.5-3.5 mm. long, the 
hairs appressed, those at the apex 1.0-1.5 mm. long. Chromosome number n = 28 from a 
Costa Rican specimen. 

Occasional, Cordillera de Talamanca, mostly on paramos above 3,100 
m. elevation; Cerro de la Muerte, Chirripo Grande. Apparently 
blooming yearlong. Plants from the highest elevations of Chirripo 
Grande are markedly smaller than average. Costa Rica to Argentina. 



A 




FIG. 36. Calamagrostis species. C. nuda: A, floret and spikelet; C. intermedia: B, 
floret and spikelet; C, inflorescence; C. pittieri: D, floret and spikelet. 



116 



BURGER: FLORA COSTARICENSIS 117 

Calamagrostis nuda (Pilger) Pilger, Bot. Jahrb. Syst. 42:60. 1908. 
Deyeuxia nuda Pilger, Bot. Jahrb. Syst. 27:29. 1899. Figure 36. 

Perennial; plants erect, in large, dense tufts up to 60 cm. in diameter; culms 45-95 cm. 
tall, unbranched, hollow, thin-walled, 1.5-2.0 mm. thick, minutely scaberulous; nodes 
purple, up to 2 mm. high, not prominent; culm leaves up to 4, the uppermost one 
reduced; sheaths much shorter than the internodes, the lower ones breaking down into 
stiff fibers, lower sheaths sometimes with a few scattered weak appressed long hairs, 
otherwise glabrous; ligule 3.5-5.0 mm. long, a firm rounded membrane, decurrent on the 
sheath margins; blades stiff, strict, mostly involute, up to 5 mm. wide when unrolled, 2 
mm. thick when rolled, smooth or scabrid beneath, scabrous-puberulent and deeply 
grooved above. Peduncle included or exserted up to 17 cm.; inflorescence a solitary 
terminal panicle, densely cylindrical, lobed, purple, 12-15 cm. long, 1.0-1.5 cm. thick, the 
spikelets densely overlapping on the short, erect branches, short-pedicellate; pedicels 
and branches scabrous. Spikelets laterally compressed, purple or greenish, disar- 
ticulating above the glumes, 3.7-4.1 mm. long, the glumes subequal, exceeding the 
floret; first glume 1-nerved, the second sometimes weakly 3-nerved, both strongly 
keeled, scabrous on the upper half of the keel, ovate, acuminate; lemma ovate, 3.3-3.5 
mm. long, the tip erose or 4-toothed; callus hairs scant or lacking, usually less than 0.5 
mm. long; back of lemma scabrous; awn inserted near the base of the lemma, rather thick 
and scarcely twisted or geniculate, slightly exceeding the lemma and exserted at the tip 
of the glumes, 3.3-3.4 mm. long; palea slightly shorter than the lemma, 2.8-3.3 mm. long; 
anther 1, yellow or purple, 1.2-1.5 mm. long; rachilla internode 0.7-1.0 mm. long, naked 
or with a few short hairs. Chromosome number n = 35 from a Costa Rican specimen. 

High paramos, 3,300-3,500 m. elevation; Asuncion, Buena Vista, 
Chirripo Grande. January and July. This species was previously 
known only from South America. 

Calamagrostis pittieri Hack., Oesterr. Bot. Z. 52:108. 1902. 
Figure 36. 

Perennial; plants 30-100 cm. tall, erect, the bases of the culms often decumbent; culms 
unbranched, glabrous or rarely with a few weak hairs below the nodes, 1-3 mm. thick, 
hollow; nodes mostly glabrous, yellow or purple; sheaths mostly shorter than the inter- 
nodes, retrorsely pilose or the upper ones glabrous; ligules 1.0-3.0 mm. long, mem- 
branaceous; leaf blades 10-30 cm. long, 3-6 mm. wide, ridged and pilose above, flat or 
folded. Peduncle included or exserted up to 26 cm.; inflorescence solitary, terminal, a 
loosely cylindrical panicle, tapering to a narrow apex, the ascending branches densely 
clothed with overlapping spikelets. Spikelets often purplish, silky because of the evident 
rachilla hairs, overlapping, appressed along the branches; pedicels short, scabrous. 
Spikelets laterally compressed, 5-6 mm. long; glumes subequal, lance-attenuate, 5-6 
mm. long; scabrous on the keels, often purple-striate, the first 1-nerved, the second 
weakly 3-nerved; floret disarticulating above the glumes and shorter than them; lemma 
3.8-4.5 mm. long, lanceolate, the callus acute, sparsely bearded with hairs less than 1 
mm. long; nerves faint; awn 4.2-5.7 mm. long, geniculate, twisted below, exserted from 
the glumes, attached between 2 acuminate apical teeth 1.2-1.7 mm. long; palea 2.8-3.5 
mm. long, the apex bidentate; anthers 2, 1.2-1.4 mm. long; caryopsis spindle-shaped, 2.0 
mm. long, soft and pasty; rachilla internode 1.3-2.1 mm. long, heavily bearded with 
white hairs, those at the apex ca. 2.5 mm. long. Chromosome number n = 14 from a 
Costa Rican specimen. 



118 FIELDIANA: BOTANY 

Paramos of the Cordillera de Talamanca: Buena Vista, Asuncion, 
Chirripo Grande; brushy roadsides in Quercus forests; elevations 
2,700-3,450 m. July to October. Apparently confined to Costa Rica. 

CENCHRUS Linnaeus 

REFERENCE: D. G. DeLisle, Taxonomy and distribution of the genus 
Cenchrus, Iowa State Univ. J. Sci. 37:259-351. 1963. 

Plants annual or perennial, caespitose, the culms solid or hollow, often decumbent and 
rooting at lower nodes. Inflorescences terminal on the culms or on leafy branches; 
inflorescence unbranched, a dense spike of detachable involucres, borne singly at the 
nodes of a flattened, flexuous rachis; each involucre (fascicle or bur) consisting of numer- 
ous bristly hairs or flattened retrorsely barbed spines, these more or less connate at the 
base and permanently enclosing several sessile spikelets. Spikelets dorsally compressed; 
first glume 1-3-nerved, usually about half as long as the spikelet; second glume and lower 
lemma subequal, as long as the spikelet; second glume 1-7-nerved; lower lemma her- 
baceous, ovate, acuminate, 3-7-nerved, containing a 2-nerved palea about equal in size 
and usually a staminate flower with enlarged anthers; upper floret perfect-flowered, the 
lemma chartaceous, 5-7-nerved, ovate and acuminate, its margins enveloping the edges 
of the palea, not inrolled; palea broad, acuminate, 2-nerved, chartaceous, equal to the 
lemma; flower lacking lodicules; anthers 3; caryopsis elliptic or ovoid, plump. 

A genus of about 20 species, widespread in temperate and tropical 
regions of both eastern and western hemispheres. The plants are found 
frequently on disturbed or sandy soils. Cenchrus is closely related to 
Pennisetum, differing in the connate spines, but some species have 
been shifted from one genus to the other. Setaria, Anthephora, and 
the subgenus Paurochaetium of Panicum are also in the same affinity 
group. Cenchrus plants are readily recognizable in most cases by the 
pungent adhering burs, by which the spikelets are readily dispersed by 
man and animals. The spines inflict painful puncture wounds which 
readily become infected. (Panicoideae: Paniceae.) 

KEY TO SPECIES OF Cenchrus 

la. Spines and bristles retrorsely barbed, so that burs readily adhere to objects when 
brushed upwardly 2 

Ib. Spines antrorsely scabrous, not adhering when brushed upwardly C. pilosus 

2a. Spines separate to base of bur, spikelet exposed between them C. myosuroides 

2b. Lower half of spines united into flat plates, forming a more or less solid bur 

concealing the spikelets 3 

3a. Burs with a ring of slender bristles at the base, much finer than flattened inner 
spines of bur 4 

3b. Burs lacking outer ring of bristles, all spines about the same size C. incertus 

4a. Inflorescence very dense, the burs completely hiding rachis; internodes of rachis 
between 2 adjacent burs less than 2 mm. long; body of burs (excluding the 



BURGER: FLORA COSTARICENSIS 119 

spines) less than 4.5 mm. wide, burs stramineous; some outer bristles about as 

long as the bur C. brownii 

4b. Inflorescence not dense, rachis partly visible between burs; rachis internodes 
2-3 mm. long; body of burs 3.5-6.0 mm. wide; burs often purplish; outer bristles 
usually less than half as long as bur C. echinatus 

Cenchrus brownii Roem. & Schult., Syst. Veg. 2:258. 1817. C. 
viridis Spreng., Syst. Veg. 1:301. 1825. Figure 37. 

Duration indefinite; culms erect to long-decumbent and rooting at the lower nodes, 
25-95 cm. long, glabrous, solid or hollow; sheaths mostly longer than the internodes, 
keeled, the margins more or less pilose; ligules 0.6-1.3 mm. long, ciliate; blades flat, 8-30 
cm. long, 4-11 mm. wide, the upper surface sometimes pilose. Inflorescences terminal on 
leafy branches, 3-12 cm. long, densely cylindrical, 1.0-1.5 cm. wide. Burs globose, 2.0-4.5 
mm. wide (5-8 mm. including the bristles), the stipe and lower parts of the spines villous; 
some outer bristles as long as the bur; inner spines flattened, often bent and interlocking; 
both spines and bristles retrorsely barbed. Spikelets 2-3 per bur, sessile and perma- 
nently attached at the base of the bur, dorsally compressed, 4-6 mm. long; first glume 
0.5-2.5 mm. long, 1-nerved; second glume 2.2-4.9 mm. long, 3-5-nerved; lower lemma 
3.5-5.5 mm. long, its palea equal; upper floret perfect flowered; lemma 3.6-5.4 mm. long, 
ovate-acuminate, glabrous; anthers 3, 0.8-2.3 mm. long. Chromosome number n = 17 
from a Costa Rican specimen. 

Roadsides, pastures, beaches, waste ground; common in 
Guanacaste, scattered elsewhere; elevations sea level to 100 m. , rarely 
to 600 m. June to October. Florida Keys; Rio Grande Valley; West 
Indies; Southern Mexico to northern South America, rarely elsewhere; 
introduced in South Africa, the Philippines and tropical Asia. 

This species is very closely related to C. echinatus, differing in the 
much denser inflorescence, smaller burs, shorter rachis internodes, 
and in usually being diploid. 

Cenchrus echinatus L., Sp. PI. 1050. 1753. C. insularis Scribn. ex 
Millsp., Publ. Field Mus., Bot. Ser. Vol. 11:26. 1900. Figure 37. 

Duration indefinite; culms 15-85 cm. long, glabrous, solid or hollow, ascending from 
long-decumbent and rooting bases; branching abundant from the decumbent culm bases; 
sheaths keeled, mostly overlapping, glabrous to heavily pubescent; ligules 0.7-1.7 mm. 
long, ciliate; blades flat, 4-26 cm. long, 3.5-11 mm. wide, glabrous or with scattered long 
weak hairs on the upper surface near the base. Inflorescences terminal on leafy 
branches, exserted, cylindrical, 2-10 cm. long, up to 2 cm. wide, the burs spaced, the 
flexuous rachis often visible between them; rachis internodes 2-3 mm. long. Burs 
globose, 5-10 mm. long, 3.5-6.0 mm. wide; outer slender bristles much shorter than the 
flat, mostly erect inner spines; color of burs often purplish. Spikelets 2-3 per bur, dor- 
sally compressed, sessile within the bur and permanently attached to it, 5.0-7.0 mm. 
long; first glume 1.3-3.4 mm. long; second glume 3.8-5.7 mm. long, 3-6-nerved; lower 
lemma 4.5-6.4 mm. long, the palea slightly longer, scabrous; upper lemma 4.7-7.0 mm. 
long, ovate-acuminate; anthers 0.8-2.4 mm. long. Chromosome number in recent Ameri- 
can specimens, n = 34. 




FIG. 37. Cenchrus species. C. echinatus: A, bur; C. incertus: B, bur; C. pilosus: C, 
bur; C. brownii: D, bur; E, plant and inflorescence. 



120 



BURGER: FLORA COSTARICENSIS 121 

Beach of Caribbean Sea, between Rio Banano and the Limon Air- 
port; beach at Tortugero; Cahuita. July to September, probably year- 
long. Transcontinental in the southern United States, southward to 
southern South America; West Indies. Introduced in the Pacific Is- 
lands, China, and Australia. 

This species is closely related to C. brownii, differing in the more 
open inflorescence, short outer bristles of the burs, and larger bur size, 
as well as in the chromosome number. 

Cenchrus incertus M. A. Curtis, Boston J. Nat. Hist. 1:135. 1835. 
C. pauciflorus Benth., Bot. Voy. Sulph. 56. 1844. Figure 37. 

Duration indefinite; plants decumbent to erect, the culms 5-80 cm. long, sometimes 
stoloniferous or rhizomatous on shifting sands; branching abundant; culms round, 1-2 
mm. thick, glabrous, solid with a pithy center; leaf sheaths keeled, longer or shorter 
than the internodes, glabrous to pilose, the upper margins and throat pilose; ligule 
ciliate, 0.5-1.5 mm. long; leaf blades flat or folded, 2-18 cm. long, 2-6 mm. wide, glabrous 
beneath, loosely pilose above. Inflorescences terminal on leafy branches, 2.0-8.5 cm. 
long, 8-20 mm. wide, cylindrical, the rachis flexuous, visible between the burs; inter- 
nodes 2.0-5.0 mm. long. Burs (fascicles) stramineous to purplish, the body ovoid to 
globose, split on 2 sides, pubescent, 5-10 mm. long, the body 2.5-5.5 mm. wide, the stipe 
up to 2 mm. long; spines 8-40, more or less flattened, to 2 mm. wide, retrorsely barbed, 
2.0-2.5 mm. long. Spikelets sessile and permanently attached within the bur, 2-4 per 
bur, dorsally compressed, 3.5-5.8 mm. long; first glume 1.0-3.3 mm. long, 1-nerved; 
second glume 2.8-5.0 mm. long, 5-7-nerved, ovate-acuminate; lower lemma similar, 
3.0-5.9 mm. long, 4-7-nerved, the palea 3.5-6.2 mm. long; fertile lemma chartaceous, 
3.4-6.0 mm. long, ovate-acuminate, 3-nerved, the broad margins covering the margins of 
the palea but not inrolled, glabrous; anthers 3, 0.5-2.0 mm. long. Chromosome number 
n = 17 from a Costa Rican specimen. 

Sandy beaches near ports, Puntarenas, Boca de Barranca, Puerto 
Limon; June and July, but probably blooming yearlong; possibly intro- 
duced. Transcontinental in the southern United States, southward to 
Panama; West Indies; central South America. 

Cenchrus myosuroides H.B.K., Nov. Gen. & Sp. 1:115, t. 35. 1816. 

Caespitose perennial, from a hard base; plants 0.5-2.0 m. tall, erect or leaning, 
branching from the base or the lower culm nodes; prophylla prominent, up to 6 cm. long; 
culms glabrous, round, thick-walled, with a small lumen; nodes dark, glabrous; sheaths 
glabrous, longer than the internodes, keeled toward the apex; ligule a short, thick 
membrane, crowned with a circle of hairs longer than the membrane, in total 1.5-3.4 
mm. long; leaf blades flat, glabrous or slightly pilose, strongly scabrous-margined, 12-38 
cm. long, 4-13 mm. wide. Inflorescence a solitary narrowly cylindrical terminal spike of 
fascicles, borne on a short glabrous peduncle; length 6.5-23 cm., thickness 0.6-1.5 cm.; 
rachis puberulent, the internodes up to 1.7 mm. long. Burs numerous, 3.8-8.1 mm. long, 
1.2-3.0 mm. thick, with a short, thick basal stipe; spines numerous, 3-6 mm. long, 
retrorsely barbed, 0.2-0.6 mm. thick; spikelets usually 1 per bur, rarely 2-3. Spikelets 
ovoid, acute, 3.8-5.6 mm. long; first glume deltoid, acute, 1-nerved, 1.5-3.0 mm. long; 



122 FIELDIANA: BOTANY 

second glume 3.1-5.0 mm. long, ovate, acute, 3-5-nerved, the margins clasping the 
sterile lemma; palea of sterile lemma lacking or present as a tongue-shaped membrane 
nearly as long as the lemma; anthers not seen; fertile lemma ovoid, 3-5-nerved, 3.8-5.4 
mm. long, acute; palea about equal, grooved; anthers 3, 1.2-2.2 mm. long; caryopsis 
elliptical, tan, 1.5-2.6 mm. long. 

The only Central American specimen is the following. Costa Rica: 
Limon, Uvita, 17 July 1932, Stork 3218, F. Southern Florida; Carib- 
bean Islands; southern Texas, Mexico; South America to central 
Argentina. 

Cenchrus pilosus H.B.K., Nov. Gen. & Sp. 1:116, t. 36. 1816. 
Figure 37. 

Duration indefinite; plants erect to decumbent, the culm bases rooting; culms 30-70 
cm. long, 2-3 mm. thick, round, solid, or hollow, glabrous; branching abundant; 
prophylla prominent, up to 30 mm. long; sheaths keeled, longer or shorter than the 
internodes, glabrous or scabrous; ligules 0.5-1.6 mm. long, ciliate; blades flat, 6-30 cm. 
long, 4-11 mm. wide, glabrous or the upper surface long-pilose near the base. Peduncles 
exserted; inflorescence a dense spike of fascicles (burs), terminal on the main culm or on 
leafy branches, 2-13 cm. long, up to 2 cm. thick, including the spreading bristles; 
spikelets borne in densely overlapping burs on a strongly angled but not zig-zag rachis, 
its nodes pilose. Burs numerous, globose, the body 5.0-8.0 mm. long, 3.0-5.5 mm. wide, 
but appearing much larger because of the spreading outer bristles, tan or purplish, the 
flattened obconical basal stipe and the flattened interlocking inner spines pilose; spines 
3.0-6.0 mm. long; outer bristles numerous, many twice as long as the spines, both spines 
and bristles antrorsely scabrous, the burs not clinging to objects as in the other species. 
Spikelets 2-3 per bur, dorsally compressed, 6.0-7.5 mm. long; first glume 1.0-4.0 mm. 
long; second glume caudate-ovate, the broad margins embracing the palea but not in- 
rolled; anthers 3, 0.9-1.8 mm. long; caryopsis ovoid, 2.2-3.0 mm. long. Chromosome 
number n = 17 from Costa Rican specimens. 

Common around Canas and scattered elsewhere in Guanacaste; 
Atenas; elevations up to 600 m.; savannas, pastures, roadsides. June to 
November. Southern Mexico and Yucatan to Costa Rica; northwestern 
South America. 

CHAETIUM Nees 

REFERENCE: M. B. Montiel, Determination taxonomica de la especie 
Chaetium bromoides (Presl) Benth. basada en el estudio anatomico, 
Revista Biol. Trop. 20:45-79. 1972. 

Caespitose perennial; inflorescence a dense erect panicle; spikelets lanceolate, dorsally 
compressed, plano-convex, with a sharp pubescent callus formed of the base of the first 
glume, united with the rachilla internode; glumes equal, herbaceous, both longer than 
the florets, both bearing long awns; sterile and fertile lemmas equal, chartaceous, ta- 
pering into short awns; edges of fertile lemma enclosing the margins of the palea, not 



BURGER: FLORA COSTARICENSIS 123 

inrolled; palea firm, flat, tapering to an awn-tip, nearly as long as the lemma; disarticula- 
tion at the base of the callus, very oblique. (Panicoideae: Paniceae.) 

Chaetium bromoides (Presl) Benth. ex Hemsl. , Biol. Centr. Amer. 
Bot. 3:503. 1885. Berchtoldia bromoides Presl, Rel. Haenk. 1:324, pi. 
43. 1830. Figure 38. 

Caespitose perennial, rarely producing stolons; culms erect or spreading, 50-100 cm. 
tall, simple or somewhat branched above; prophylla prominent, 5-9 cm. long, pubescent 
near the tip; culms 2-3 mm. thick, glabrous and shining, hollow, the cavity small; nodes 
upwardly bearded or glabrescent; leaf sheaths keeled, shorter than the internodes, 
glabrous except for the upper margins and the collar; ligules prominent, 1.5-2.5 mm. 
long, of densely crowded white hairs; blades 10-30 cm. long, 3-7 mm. wide, sparsely 
papillose-pilose on both surfaces, rarely puberulent as well; peduncles included or ex- 
serted as much as 30 cm.; panicles terminal on the culm or on leafy branches, 10-23 cm. 
long, 1-2 cm. wide, the branches erect and appressed; spikelets greenish or purple, 
dorsally compressed, plano-convex, 8-10 mm. long (excluding awns); disarticulation 
below the glumes, at the base of a slender pilose callus 1.5-2.5 mm. long formed by the 
union of the first glume and the lower rachilla joint; disarticulation very oblique; glumes 
subequal, lanceolate, the first 7-10 mm. long, the second 6-8 mm., both broad and 
concealing the florets, 5-7-nerved, scabrid on the nerves, tapering into erect awns 10-35 
mm. long; sterile lemma 6-8 mm. long, smooth and glabrous, narrowly ovate, faintly 
3-nerved; fertile floret 6-8 mm. long; lemma smooth, chartaceous, the margins flat, 
covering the margins of the palea; lemma with an awn up to 2 mm. long; nerves faint; 
anthers 3, purple, 1.5 mm. long. Chromosome number n = 13 from Costa Rican speci- 
mens. 

Common in the Meseta Central; open or partially shaded areas; 
lawns, roadsides, disturbed areas; 1,000-2,000 m. elevation. Blooming 
apparently occurs throughout the year. Mexico to Costa Rica. 



CHLORIS Swartz 

REFERENCE: D. Anderson, Taxonomy of the genus Chloris 
(Gramineae), Brigham Young Univ. Sci. Bull, Biol. Ser. 19:2:1-132. 
1974. 

Annual or perennial caespitose, stoloniferous or rhizomatous grasses; culms solid, 
pithy. Inflorescence of 1 or more whorls of 1-sided spikes; spikelets sessile or nearly so, 
appressed in 2 rows along the lower sides of a slender triquetrous rachis. Spikelets 
laterally compressed, disarticulating above the glumes; glumes narrow, acuminate, 1- 
nerved; fertile florets 1-several, the lemma 3-nerved, the lateral nerves marginal; nerves 
usually ciliate, especially above; callus bearded; awn inserted just below the bifid apex of 
the lemma; palea about equal to the lemma; rachilla prolonged beyond the fertile floret 
and bearing 1 to several rudimentary lemmas. 

A large genus of grasses of warm climates of both Old and New 
Worlds. The genus is related to Eustachys, Bouteloua, and Gymnopo- 



J&t 



B 



FIG. 38. Ckaetium bromoides. A, inflorescence; B, two views of a spikelet; C, fertile 
floret. 



124 



BURGER: FLORA COSTARICENSIS 125 

gon. Some of the species are common tropical weeds, and one, C. 
gay ana, is an important forage grass. (Chloridoideae: Chlorideae.) 

KEY TO SPECIES OF Chloris 

la. Florets 3-5, the lowermost 1 or 2 producing grains, upper ones sterile or rudimen- 
tary; cultivated crop C. gayana 

Ib. Florets 2, second sterile and rudimentary; wild plants 2 

2a. Spikelets 2.5-3.5 mm. long, greenish; fertile lemma 2.5-3.4 mm. long; spikes 

somewhat flexuous C. radiata 

2b. Spikelets 3.8-4.1 mm. long, purple-tinged; fertile lemma 3.4-4.0 mm. long; 
spikes stiff C. aristata 

Chloris aristata (Cerv.) Swallen, N. Amer. Fl. 17:8: 596. 1939. 
Agrostomia aristata Cerv. Naturaleza 1: 345. 1870. ? Chloris rufes- 
cens Lag.?, Varied. Ci. 4:143. 1805. Figure 39. 

Duration indefinite; plants forming small circular patches, the culms arising from short 
stoloniferous bases; culms unbranched, 15-60 cm. tall, 2 mm. thick, solid, pithy, gla- 
brous; nodes dark, contracted; sheaths shorter than the internodes, strongly keeled, 
glabrous, glaucous; ligule a short membrane, densely ciliate with a dense row of stiff 
white hairs, ca. 1 mm. long; leaf blades flat or folded, blunt-tipped, 1-13 cm. long, 1.5-4.0 
mm. wide, the uppermost usually much reduced, scabrous especially on the margins and 
on the keeled midrib below, often bearing scattered long weak hairs. Peduncle exserted 
4-15 cm., pilose at the apex; inflorescence vase-shaped, of 5-7 spikes, mostly in a single 
whorl, or with a solitary spike attached just below the others; spikes 3-8 cm. long; 
spikelets appressed in 2 rows along the lower side of the slender triquetrous rachis, 
overlapping. Spikelets 3.8-4.1 mm. long, the glumes and lemmas keeled; glumes 1- 
nerved, subulate to narrowly lanceolate, acuminate, scabrous on the keel; first glume 
2.0-2.2 mm. long, the second 3.2-4.0 mm. long; fertile lemma 3.4-4.0 mm. long, ovate, 
acute, the keel bowed out; slightly bifid at the apex, the awn 9-10 mm. long, attached 
about one-fourth below the apex; lateral nerves marginal, ciliate on the upper half; callus 
short-bearded; palea equal to the lemma or slightly longer, the lower part infolded 
around the rachilla segment, the upper half dilated, scabrous-ciliate on the upper mar- 
gins; anthers 3, yellow, 0.5-0.8 mm. long; rachilla segment slender, ca. half the length of 
the fertile lemma, rudiment 1.7-2.0 mm. long, cylindrical, truncate, consisting of an 
empty lemma bearing an awn 2.5-4.0 mm. long; spikelets often purplish. Chromosome 
number n = 50. 

Occasional; roadsides and open areas, mostly in the Meseta Central; 
Palmares. Blooming apparently yearlong. Mexico and Guatemala; 
Costa Rica. 

This is the species which was called C. orthonoton Doell in Grasses 
of Central America. That species, however, is Brazilian and differs in a 
number of characters from C. aristata. 

Chloris gayana Kunth, Rev. Gram. 1:89. 1829. 

Vigorous stoloniferous perennial; plants up to 1.5 m. tall; stolons stout, elongated; 
erect branches arising freely from the nodes; prophylla prominent, 2-3 cm. long; culms 




FIG. 39. Chloris species. C. aristata: A, inflorescence; B, spikelet; C. radiata: C, 
spikelet. 



126 



BURGER: FLORA COSTARICENSIS 127 

glabrous, solid, pithy; nodes glabrous, contracted; sheaths glabrous, somewhat keeled; 
ligule a minutely ciliolate membrane, 0.3-0.5 mm. long, a conspicuous tuft of stiff 
papillose-based hairs borne just behind it; blades flat, acuminate, 20-45 cm. long, 4-7 
mm. wide, glabrous or scabrous, sometimes with scattered long papillose-based hairs on 
the upper surface. Inflorescences terminal on the culms, consisting of a single dense 
whorl of 6-16 rather thick, somewhat flexuous spikes, each 5-9 cm. long, the spikelets in 
2 somewhat overlapping rows on the lower sides of the triquetrous rachis. Spikelets 3-5 
mm. long, disarticulating only above the glumes; florets 3-5, the lower 1 or 2 producing 
grains, the upper ones staminate or sterile; lower lemma 2.7-3.8 mm. long, ovate, pubes- 
cent on the callus and marginal nerves, the hairs longer near the apex; awn 2-4 mm. long, 
flexuous, attached just below the apex of the lemma; palea slightly longer than the 
lemma; upper lemmas glabrous, successively shorter than the first lemma, the ultimate 
one a small obconical empty rudiment; anthers 3, yellow, ca. 2 mm. long. 

Native to Africa; cultivated in the grass garden at the IICA at 
Turrialba; possibly cultivated for forage elsewhere. "Rhodes grass." 

Chloris radiata (L.) Swartz, Prodr. Veg. Ind. Occ. 26. 1788. Agros- 
tis radiata L., Syst. Nat. 10. 2:873. 1759. Figure 39. 

Duration indefinite; plants spreading by short stout freely branching stolons and 
making circular patches; culms erect to spreading, 15-60 cm. long; prophylla prominent, 
up to 4 cm. long; culms solid, pithy, glabrous, flattened; foliage glaucous, scabrous, 
glabrous or softly hirsute; sheaths strongly flattened and keeled; ligule a minutely cilio- 
late membrane, 0.5-0.7 mm. long; leaf blades 6-12 cm. long, 3-5 mm. wide, strongly 
keeled, especially near the base, blunt-tipped, scabrous on the margins and midrib, 
sometimes on the surface, usually hirsute above, sometimes on both surfaces; dewlap 
prominent. Inflorescence solitary, terminal, vase-shaped, of 1-2 closely spaced whorls of 
lax spikes, each 3.5-7.0 cm. long; spikes 4-18 per inflorescence; spikelets appressed in 2 
rows along the lower sides of the slender triquetrous rachis. Spikelets laterally com- 
pressed, 2.5-3.5 mm. long, the glumes and lemmas keeled; first glume linear, 1.5-2.4 
mm. long, 1-nerved; second glume similar, 2.2-3.4 mm. long; fertile lemma 2.5-3.4 mm. 
long, narrowly ovate, strongly keeled, firm, slightly roughened, the marginal nerves 
short-ciliate on the upper half, slightly bifid at the tip, the awn 7-11 mm. long, arising 
between the teeth of the lemma; callus short-ciliate; palea equal to the lemma; rachilla 
segment slender, half as long as the lemma, bearing a slender rudiment 0.5-1.5 mm. 
long, mostly concealed by the fertile lemma; awn of rudiment 2.0-7.5 mm. long; anthers 
3, yellow, 0.5 mm. long. Chromosome number n = 20 from Costa Rican material. 

Common in open, disturbed areas, cafetales, banana plantations, 
cacao groves; sea level to 1,300 m. elevation, on both Caribbean and 
Pacific slopes. Blooming apparently yearlong. Mexico to Paraguay; 
West Indies. 



CHUSQUEA Kunth 

REFERENCES: E. G. Camus, Les Bambusees: Monographic, biologic, 
culture, principaux usages, Lechevalier. Paris. Text and Plates. 1913. 
F. A. McClure, Genera of bamboos native to the New World. 



128 FIELDIANA: BOTANY 

(Gramineae: Bambusoideae), Smithsonian Contr. Bot. 9:1-148. 
Smithsonian. Washington, D.C. 1973. Wm. Munro, A monograph of 
the Bambusaceae, including descriptions of all the species, Trans. 
Linn. Soc. London 26:1:1-157 + 6 Tab. 1868. 

Bamboos of small to moderate stature; rhizomes pachymorphous or occasionally lep- 
tomorphous; culms arching, the upper portions often drooping or trailing; branching 
from middle and upper nodes; internodes solid, rarely with a small irregular lumen by 
disintegration of the central parenchyma; branching usually with a single large primary 
branch just above the node, subtended by a fascicle of few-many shorter, foliage-bearing 
branchlets; primary branch bud sometimes not developing into a branch and remaining 
concealed by the minor branchlets. Inflorescences terminal on the leafy branchlets, 
variously open or dense panicles or rarely reduced to a small raceme of few spikelets. 
Spikelets narrowly ovate, acute or acuminate, sometimes short-awned; glumes much 
shorter than the spikelet, sometimes rudimentary, nerveless or 1-3-nerved; disarticula- 
tion above the glumes, the remainder of the spikelet shed as a unit; sterile lemmas 2, 
similar, from half as long to nearly as long as the spikelet; fertile lemma ovate, acute or 
awn-tipped, rounded or flattened on the back, 5-13-nerved; palea about as long as the 
lemma or slightly exceeding it, usually grooved between the keels, 4-8-nerved; lodicules 
3, flat, ovate or spatulate, vasculated, usually ciliate on the upper half; anthers 3, large; 
ovary beaked or with a short style; stigmas 2. 

Chusquea is a large genus of montane bamboos, ranging from 
Mexico to southern South America. Vegetatively, the plants are usu- 
ally distinguished by the solid culms and the branching pattern of one 
large primary branch and numerous small, foliage-bearing branches. 
The spikelets are rather uniform in structure and, on the rare occa- 
sions when the plants are in bloom, furnish good clues to identity. 
Recently, McClure has segregated the genus Swallenochloa for the 
high-altitude forms with fewer, more strict branches and an irregular 
lumen in the internodes. The distinctions are not sharp, and our 
chromosome studies have indicated that both genera have a haploid 
chromosome number of n = 20, a somewhat unusual number in the 
bamboos. Some species of Bambusa, subgenus Guadua may also have 
solid or nearly solid internodes at times. They can usually be dif- 
ferentiated by the possession of branch thorns and by their low- 
altitude habitats. 

Chusquea is an extremely complex genus, and we are not yet able to 
name all collections. The treatment offered here is tentative. A few 
distinctive, but as yet unnamed, populations are briefly discussed at 
the end of this generic treatment. (Bambusoideae: Chusqueae.) 

KEY TO SPECIES OF Chusquea 

la. Culms of mature plants 1 cm. or less thick 2 

Ib. Culms of mature plants usually 2-5 cm. thick 4 



BURGER: FLORA COSTARICENSIS 129 

2a. Leaf blades 7.5-17 cm. long, 16-23 mm. wide, ovate, 3-5 x longer than wide 

C. virgata 

2b. Leaf blades 1-9 cm. long, 2-12 mm. wide, ovate, 5.7-7 x longer than wide . 3 

3a. Leaf blades on foliage-bearing branchlets 1-2.5 cm. long, 2-4 mm. wide; base of leaf 

blades with tuft of woolly hairs on one side of midrib on abaxial surface; internodes 

of culms smooth C. coronalis 

3b. Leaf blades on foliage-bearing branchlets 5-9 cm. long, 8-14 mm. wide; base of leaf 
blades woolly on both sides of midrib on abaxial surface; internodes of culms scab- 
rous C. simpliciftora 

4a. Leafy branches interspersed with thin, curly, leafless, fibrillar branchlets, up to 

10 cm. long C. scabra 

4b. Leafy branchlets not interspersed with fibrillar branchlets 5 

5a. Lowermost 10-20 nodes of the culms bearing circlets of short, protruding root thorns 

up to 10 mm. long C. pittieri 

5b. Root thorns absent, lower nodes of culms sometimes with soft, drooping adventiti- 
ous roots 6 

6a. Ligule 1.5 mm. or less long; leaf blades narrow, 14-51 x longer than wide, not 

conspicuously tessellate 7 

6b. Ligule 2-10 mm. long; leaf blades 6-14 x longer than wide, strongly tessellate 8 

7a. Leaf blades 7-12 mm. wide, 14-32 x longer than wide C. longifolia 

7b. Leaf blades 4.5-7 mm. wide, 23-51 x longer than wide C. meyeriana 

8a. Leaf blades 10-14 x longer than wide, margins not conspicuously white-banded; 
texture thin; base of blade tapering to the pseudopetiole; widespread in the 

mountains C. tonduzii 

8b. Leaf blades 6-9 x longer than wide, base rounded or subcordate; margins con- 
spicuously white-banded; Poas, Irazii, Turrialba . . Swallenochloa vulcanalis 

Chusquea coronalis Sods. & Cald., Brittonia 30:158. 1978. 
Figure 40. 

Caespitose in small clumps of 2-3 culms; rhizomes pachymorphous; culms to 3-5 m. tall; 
internodes ca. 1 cm. thick, smooth, cylindrical, solid; sheath girdle retrorsely bearded; 
primary branch buds usually developing, the primary branches slender, up to 70 cm. 
long; foliage-bearing branchlets on the main culm or on the primary branches numerous, 
up to 70 per node of the primary culm or in smaller fascicles on the branches; foliage- 
bearing branchlets very slender, simple, 5-11 (-17) cm. long, in blooming specimens with 
1-2 leaves; nodes minutely retrorsely bearded; sheath glabrous; ligule minute; blades 
flat, 1-2.5 cm. long, 2-4 mm. wide, glabrous except for a minute tuft of hairs on one side 
of the midrib on the abaxial surface just above the base. Inflorescences terminal on the 
foliage-bearing branchlets; peduncle slender, exserted up to 4 cm.; inflorescence a 
raceme or slender simple panicle, 2-4 (6) cm. long, ca. 5 mm. wide, with a few appressed 
branches bearing 1-3 spikelets each, most of the spikelets borne racemosely on the 
rachis; pedicels ascending or appressed, slender, up to 7 mm. long; spikelets usually 2-10 
per panicle, rarely up to 30, appressed to the rachis. Spikelets dorsally compressed, 
stramineous or purplish, papery, 5.0-5.5 mm. long; glumes reduced to a minute cupule, 
0.2-0.3 mm. long at the tip of the pedicel; disarticulation above the glumes, the remain- 
der of the spikelet falling as a unit; first sterile lemma 2.3-2.7 mm. long, ovate ca. 2:1, 
blunt, 1-nerved, ciliolate near the tip; second sterile lemma similar, 2.7-3.0 mm. long; 






FIG. 40. Chusquea coronalis. A, culm sheath; B, inflorescence; C, spikelet; D, surface 
of culm sheaths, square is 0. 1 mm. 



130 



BURGER: FLORA COSTARICENSIS 131 

fertile floret dorsally compressed, the lemma 5.0-5.1 mm. long, ovate, acute, strongly 
ridged and grooved, 8-9-nerved, ciliolate near the tip; palea about equal or slightly 
longer, 4-nerved, bidentate at the tip, ciliolate on the upper margins, grooved between 
the keels; lodicules 3, flat, vasculated, long-ciliate at the tip; anthers 3, yellow, 3.2-3.5 
mm. long; style very short; stigmas 2. The description was taken from the specimen 
cited below. 

Costa Rica: Prov. San Jose, Canyon of Rio Jerico, 2 km. NW of Rio 
Conejo, 84 5' W, 9 48' N, elevation 1,200 m., 11 June 1976, Pohl & 
Pinette 13209, ISC, US, F, CR. The following specimen appears to be 
the same species, but is in vegetative condition. Foliage leaves are 
larger and more numerous, but have the same pubescence pattern. 
Primary culm sheaths are densely splotched with purple and are 
strongly hispid with appressed, papillose-based rigid hairs. Some of 
the larger branchlets have enlarged foliage leaf blades on the branch 
axis, as well as clusters of small branchlets bearing small foliage leaves 
at the nodes. Prov. San Jose, Forest valley of Rio Alumbre, near Rio 
Conejo, elevation ca. 1,200 m., culms 10-15 m. long, arching and 
drooping, solid, forming dense drooping veils of foliage, 6 September 
1968, Pohl & Davidse 11054, ISC, US, F, CR. 

This species is similar to C. simpliciflora Munro, but differs from it 
in the shorter spikelets with much smaller glumes, the blunt sterile 
lemmas, strongly ridged and grooved fertile lemma, and the more 
numerous spikelets. From C. heydei Hitchc., it differs in its much 
shorter spikelets with smaller glumes, in the obtuse one-nerved sterile 
lemmas, those of C. heydei being three-nerved, and in its strict, nar- 
row panicle with short-pedicellate spikelets. 

Chusquea longifolia Swallen, J. Wash. Acad. Sci. 30:210. 1940. 

Caespitose bamboo in large, dense clumps; colonial, forming large stands; culms to 10 
m. or more long, arching and drooping; internodes up to 3 cm. thick, cylindrical, smooth 
or scaberulous, solid; culm sheath (one specimen seen) 12 cm. long; ligule thick, straight 
ca. 2 mm. long; blade erect, as wide as the sheath apex, 13 cm. long, 3.5 cm. wide, 
acuminate, awn-tipped; foliage-bearing branches numerous in a dense fascicle, up to 60 
cm. long, including the inflorescence when present; primary branch bud usually de- 
veloping into a branch; leaf sheaths glabrous except for the ciliolate overlapping margin; 
external ligule evident; sheath apex with rounded stiff auricles; internal ligule 1.0-1.5 
mm. long, membranaceous; leaf blades glabrous or with appressed or velvety pubes- 
cence beneath, mostly 14-27 cm. long, 7-12 mm. wide, the length usually 14-32 x the 
width. Inflorescence a slender dense panicle, its base usually included in the uppermost 
sheath; panicle 8-17 cm. long, 1.0-1.5 cm. wide; branches short, erect, scabrous on the 
angles, bearing spikelets to the base. Spikelets stramineous or purplish, borne on short, 
erect pedicels. Spikelets 10-15.7 mm. long, including the awn of the fertile lemma, 
subcylindric, purple, fading to stramineous, disarticulating above the glumes, the re- 
mainder of the spikelet falling as a unit; glumes acute or rounded, usually nerveless; first 



132 FIELDIANA: BOTANY 

glume 1.0-1.3 mm. long; second glume 1.4-1.8 mm. long, first sterile lemma papery, 
ovate 3.2-4.3:1, 7-9-nerved; second sterile lemma nearly as long as the fertile floret, 
papery, 8.0-12.7 mm. long, with an awn 1-3 mm. long, ovate 3.2-4.3:1, 7-9-nerved; fertile 
lemma smooth, stiff, glabrous, dorsally rounded, 9-14 mm. long, including an awn 1.0-1.5 
mm. long, ovate 3:1, 7-nerved or sometimes with an additional marginal pair of weak 
nerves; palea equal to the lemma or slightly exceeding it, 6-7-nerved, rounded to the 
keels and grooved between them; apex rigidly bidentate; lodicules 3, flat, obovate, acute, 
vasculated, long-ciliate at the tip; anthers 3, yellow, 5.1-5.4 mm. long; style short; 
stigmas 2; caryopsis oblong, 9 mm. long. 

Seedlings of this species were found in abundance growing on leaf 
litter in shade on a cliff above the highway 2.5 km. S of the Vara 
Blanca-Poas intersection in June 1976. They were all less than 10 cm. 
tall and were derived from dead fruiting plants of this species, as could 
be determined from the attached spikelet parts. Their leaf blades were 
ovate ca. 3:1, and the nodes, sheath margins, auricles, and blade sur- 
faces were pubescent. This pubescence is a juvenile feature, not seen 
in the parent plants. 

The following flowering or fruiting specimens were collected from 
Volcan Poas, and the description was largely drawn from them: P & D 
11507, Pohl & Lucas 13100, Pohl & Pinette 13217, Tonduz 10747 (cited 
by Swallen). The following flowering or fruiting specimens were ob- 
tained along the CIA near La Georgina. Their spikelets are slightly 
shorter, but are otherwise similar to the Poas material. Leaf blades 
are usually narrower and may be pubescent: Pohl & Lucas 13101, 
13112. The following flowering specimen came from the Zarcero re- 
gion: Prov. Alajuela, Palmira, elevation 6,000 ft., 18 September 1937, 
A. Smith A 412. The following vegetative specimen was from 
Hacienda Central, Volcan Turrialba. It is similar to the Talamanca 
specimens in having pubescent leaf blades: Pohl & Davidse 10867. 

Middle to high altitudes, Cordillera Central and Cordillera de 
Talamanca, at elevations of 1,700-3,100 m., mostly below the paramo. 
According to Swallen, this species ranges from Chiapas, Mexico, to 
Chiriqui, Panama. Blooming is known in Costa Rica from the years 
1896, 1937, 1968, 1974, and 1976. Our first flowering collection, from 
Poas, was from a solitary flowering culm, and no other flowering was 
seen at that time. In December 1974, we found a single large clump 
flowering, ca. 5 km. below the crater of Poas. The 1976 flowering 
involved large stands flowering gregariously in the Vara Blanca area. 

Chusquea meyeriana Ruprecht ex Doell, in Martius, Fl. Brasil. 
2:203. 1880. Figure 41. 




J&4 



FIG. 41. Chusquea meyeriana. A, culm node and branch complement; B, inflorescence 
and foliage leaves; (', spikelet; D, culm sheath, blade, and ligule. 



133 



134 FIELDIANA: BOTANY 

Caespitose bamboo; culms to 10 m. or more long, arching and drooping; internodes 
cylindrical, solid, up to 5 cm. thick, the lower nodes sometimes bearing root-thorns; 
sheath girdle prominent; internodes slightly scaberulous, especially toward the apex; 
culm sheaths sparsely hispid, especially near the base, the apex with rounded auricles 
continuous with a stiff ligule up to 5 mm. long; primary culm branch developing or not; 
foliage-bearing branches 30-60 cm. long, including the inflorescence, if present, very 
numerous in a dense fascicle; lower internodes of the foliage-bearing branchlets elon- 
gated, their sheaths bladeless; leaf blades clustered toward the tips of the branches; 
internodes puberulent; sheaths glabrous except for the ciliolate overlapping margin; 
external ligule evident; internal ligule a stiff membrane ca. 1.5 mm. long; one sheath 
auricle present; leaf blades linear 23-51:1, 14-23 cm. long, 4.5-7.0 mm. wide, sparsely 
pubescent, sometimes glaucous beneath. Peduncles well exserted; inflorescence an open 
pyramidal panicle, up to 12 cm. long, about as wide; branches solitary, widely spreading, 
2-8 cm. long; rachis, branches, and pedicels angular, scabrous on the angles; pulvini of 
primary branches evident, puberulent. Spikelets mostly appressed along the primary 
panicle branches; pedicels slender, somewhat flexuous, 2-7 mm. long. Spikelets 
stramineous, 7.8-9.5 mm. long, narrowly ovate, acute; glumes reduced, nerveless, the 
first 0.3-0.8 mm. long, the second 0.5-1.0 mm. long, acute; disarticulation above the 
glumes, the remainder of the spikelet falling as a unit; sterile lemmas papery, awn- 
tipped, the first 4.0-6.5 mm. long, ovate ca. 2.5:1, 3-nerved; second sterile lemma simi- 
lar, 4.8-6.5 mm. long, ovate ca. 3:1, 5-nerved; fertile lemma firmer, 7.2-8.5 mm. long, 
with a short awn-tip, ovate 2.4-2.7:1, 7-9-nerved; lodicules 3, flat, vasculated, ovate, 
acute, the upper half ciliate with long stiff hairs, the surface toward the tip with short 
barbs; the two exterior lodicules much wider than the third; anthers 3, pale yellow, 
3.5-5.0 mm. long; style short; stigmas 2; caryopsis not seen. 

The above description was compiled from Costa Rican material avail- 
able to me. The panicle of Lankester 105 is a reasonably good match 
for the illustration given by Camus, Monog. Bamb. pi. 50; however, we 
do not have both fruiting and vegetative material taken from the same 
stand at the same time. Costa Rican specimens that I have seen are the 
following: Prov. Cartago, Cascajal, altitude 5,500 ft., year 1919, C. H. 
Lankester 105 (flowering), NE of Cascajal, 1,700 m. elevation, 22 De- 
cember 1974, Pohl & Lucas 13089 (vegetative); Prov. Puntarenas, 
heavily wooded slopes above Monteverde, elevation 1,500 m., 8 May 
1971, R. W. Wilbur 14.254 (flowering), Forest Preserve, Monteverde, 
elevation 1,500 m., 20 June 1976, Pohl & Pinette 13248 (vegetative). 

Chusquea pittieri Hackel, Oesterr. Bot. Z. 53:153. 1903. Figure 42. 

Caespitose bamboo in open clumps of ca. 20 culms; culms arching and drooping, 10-15 
m. long, forming delicate curtains of foliage; internodes cylindrical, glabrous, solid, up to 
4 cm. thick, green when young, becoming yellow; lower 20 or more culm nodes bearing a 
ring of straight projecting root thorns, these up to 10 mm. long; culm sheaths 30-55 cm. 
long, tapering from the base to a very narrow apex; surface tawny, purple-blotched, or 
solid purple, scabrous-roughened and with scattered coarse, glassy, papillose-based his- 
pid hairs; ligule thick, rigid, up to 3.5 mm. long, coarsely hispid at the apex; sheath 




FIG. 42. Chusquea pittieri. A, inflorescence; B, culm segment with nodal root thorns; 
C, node with branch complement; D, spikelet. 



135 



136 FIELDIANA: BOTANY 

blades early deciduous, ca. 15 cm. long, 7-8 mm. wide (1 specimen seen); sheaths decidu- 
ous, but sometimes impaled by the root thorns and remaining on the culm; primary 
branches 1-several from each of the upper nodes; foliage-bearing branchlets numerous, 
delicate, up to 100 per node, 20-30 cm. long, the base of the fascicle of branchlets 
sometimes completely encircling smaller branches; lower leaf blades and sheaths of the 
foliage-bearing branchlets deciduous, the branchlet bearing 3-6 blades toward the tip; 
sheaths glabrous except for the ciliolate overlapping margin; auricles and external ligule 
ciliate with stiff, glassy hairs up to 3 mm. long; ligule a short erose membrane, ca. 0.5 
mm. long; pseudopetiole 1 mm. or less long; leaf blades flat, linear 10-20:1, 6-10 cm. long, 
4-7 mm. wide, light green, sometimes slightly glaucous; abaxial surface glabrous except 
for a dense tuft of short hairs on one side of the midrib at the base (alternating sides on 
successive leaf blades); adaxial surface with scattered weak hairs. Inflorescence a nar- 
row, rather dense panicle, 4-7 cm. long, up to 2 cm. wide; branches short, ascending, 
spikelet-bearing to their bases; spikelets overlapping; pedicels short, mostly less than 2 
mm. long, scaberulous. Spikelets dorsally compressed, 11-12.3 mm. long, acute; glumes 
much reduced, rounded or barely acute, nerveless, the first ca. 0.5 mm. long, the second 
ca. 1.1 mm. long; disarticulation above the glumes, the remainder of the spikelet falling 
as a unit; sterile lemmas 2, papery, the first 6.4-7.0 mm. long, ovate 2.3:1, 7-nerved, with 
a minute awn-tip; second sterile lemma similar, ca. 7 mm. long, 5-nerved, awn-tipped; 
fertile lemma 10.5-12 mm. long, 11-14-nerved; palea slightly longer, 7-8-nerved; apex 
bidentate; lodicules 3, flat, strongly vasculated, acute, long-ciliate above the middle; 
ovary with a slender terminal appendage and 2 stigmas; caryopses not seen. 

Moist canyons of the volcanoes of the Cordillera Central, from 
1,500-2,700 m. elevation. The following collections are known from 
Costa Rica: Finca San Juan, Volcan Barba, Pohl & Selva 12298; Bajos 
de las Nubes, Pohl & Lucas 13088; OK Corral, Pohl & Lucas 13106; 
Rio Reventado between Llano Grande and Tierra Blanca, Pohl & 
Lucas 13098; Copey, Pohl & Lucas 13140; Santa Maria de Dota; Queb- 
radillas; Cuestas de los Arrepentidos between San Marcos and Santa 
Maria de Dota, Pittier 2249 TYPE in US. 

This species is readily identified vegetatively because of the con- 
spicuous root thorns borne on many nodes from the base to the middle 
of the culm, and even on some of the primary branches. The type 
specimen, collected in 1890, was in the flowering condition. Several 
collections by Standley in 1925 also had inflorescences. I have not seen 
recent bloom. McClure, in the Flora of Guatemala, indicates that C. 
pittieri also occurs in Guatemala and Panama. 

Chusquea scabra Sods. & Cald., Brittonia 30:300. 1978. 

Caespitose bamboo in large, dense clumps, forming large colonies; culms to 10 m. long, 
2-3 cm. thick, arching, scrambling through trees, the upper portions pendent; internodes 
green, scabrous-roughened, not hispid, solid; lower nodes sometimes bearing soft roots 
up to 5 cm. long; main-culm sheaths scabrous-roughened, more or less purple-spotted; 
ligule a straight diagonal line, a thick, ciliolate membrane 0.3-0.5 mm. long with a few 
auricular hairs at its ends; culm-sheath blade as wide as the sheath apex, erect, the 



BURGER: FLORA COSTARICENSIS 137 

adaxial surface scabrous with short, stiff hairs; foliage-bearing branchlets in dense fasci- 
cles, ca. 20-30 per node, subtended by conspicuous basal bracts and prophylls; branchlets 
subequal, stiff, up to 70 cm. long, including inflorescences when present, bearing 2-3 
well-developed leaf blades toward the tip and some reduced ones below; leafy branchlets 
interspersed with numerous slender, curly, fibrillar branches up to 10 cm. long, these 
bearing reduced bladeless sheaths at their nodes; principal foliage leaf blades flat, 11-15 
cm. long, 12-15 mm. wide, ovate 8-10:1, acuminate, scaberulous on both surfaces, espe- 
cially toward the tip; margins white-banded, scabrous. Blades are glabrous in the popu- 
lations from the Irazu-Turrialba Massiv, but our collection from El Muneco has blades 
sparsely hairy beneath. Internodes of foliage-bearing branchlets glabrous; sheaths 
glabrous except for the ciliate overlapping margin; sheath auricles erect, rounded at the 
apex, up to 3 mm. long, ciliate; external ligule coriaceous, up to 1.5 mm. long; 
pseudopetioles 3-4 mm. long, margined. Inflorescences terminal on leafy branchlets; 
peduncles usually included in bladeless sheaths; panicles strict, erect, 10-24 cm. long, 
less than 1 cm. thick, the branches erect, appressed to the rachis, the lower ones up to 8 
cm. long, the upper very short, all bearing overlapping spikelets to their bases; rachis, 
branches, and pedicels angular, scabrous; lateral pedicels usually 3-8 mm. long, ap- 
pressed. Spikelets numerous, narrowly ovoid, acuminate, awn-tipped, 8.2-10.3 mm. 
long; glumes scabrous on the keels, awn-tipped, the first 1-nerved, 2.0-3.2 mm. long, 0.7 
mm. wide; second glume 3.2-4.1 mm. long, 1.1 mm. wide, 3-4-nerved, the awn up to 1.2 
mm. long; disarticulation above the glumes, the remainder of the spikelet falling as a 
unit; first sterile lemma papery, scaberulous, 4.2-5.6 mm. long, including the awn-tip, 
ovate 2.0-2.4:1; nerves 5, sometimes with 2 additional weak marginal ones; margins 
ciliolate, tapering abruptly to the awn; second sterile lemma similar, 6.2-8.0 mm. long, 
5-7-nerved, ovate 2.5-3.1:1, the awn-tip to 1 mm. long; fertile lemma dorsally flattened, 
firmer than the sterile lemmas, faintly 7-nerved, 8.0-9.3 mm. long, the palea slightly 
shorter, its margins rounded to the scabrous keels; apex bidentate; a deep groove pres- 
ent between the keels; lodicules 3, ovate, flat, strongly vasculated, the rounded tip 
long-ciliate, the margins shorter-ciliate with 1- and 2-celled microhairs; anthers 3, yel- 
low, 4.3-4.5 mm. long; style short, stigmas 2; caryopses not seen. Chromosome number 
n = 20 from Pohl & Pinette 13305. 

The following collections of this species are known: Prov. Cartago, 
Rio Coliblanco, 4 km. NE of Capellades, 1,630 m., 4 June 1976, Pohl & 
Pinette 13305 (blooming), Crossing of Rio Aquiares, W of Santa Cruz, 
1,570 m., 4 June 1976, Pohl & Pinette 13307 (young bloom), 5 km. NE 
of Capellades, 1,650 m., 11 June 1973, Pohl & Selva 12888 (vegeta- 
tive), Valley of Rio Sombrero, 2 km. S of El Muneco, 1,300 m., 7 June 
1973, Pohl & Selva 12871 (vegetative). 

This species is one of the most easily recognized of the Costa Rican 
species of Chusquea because of the scabrous internodes and the abun- 
dant basal fibrillar branchlets at the leaf-bearing nodes. Moist moun- 
tain slopes, 1,200-1,600 m. elevation. 

Chusquea simpliciflora Munro, Monogr. Bambusaceae, Trans. 
Linn. Soc. London. 26:1:54, Tab. II. 1868. 



138 FIELDIANA: BOTANY 

Vinelike bamboo; rhizomes leptomorphous; culms very elongated, to 25 m. long; inter- 
nodes less than 1 cm. thick, smooth or usually scabrous with hard points, not hispid; culm 
sheaths glabrous, purple, tapering to a filiform blade ca. 2 cm. long, its ligule a dense row 
of short hairs; foliage-bearing branchlets very slender, 20-40 cm. long, up to 50 per node; 
lower internodes elongated, naked; foliage blades 3-5, clustered toward the tip; sheaths 
glabrous or puberulent, retrorsely ciliate at the base, ciliolate on the overlapping mar- 
gin; auricles more or less ciliate; external ligule evident; internal ligule 0.5-1.0 mm. long, 
membranaceous; pseudopetiole 1 mm. or less long; leaf blades thin, 5.5-9 cm. long, 8-14 
mm. wide ovate 5.7-7.3:1 flat; abaxial surface with 3 conspicuous, whitened nerves on 
each side of the midrib, woolly on both sides of the midrib at the base, the remainder 
glabrous or sparsely appressed hairy; adaxial surface glabrous or very sparsely ap- 
pressed pubescent, the midrib scabrous. Inflorescence a short raceme of 2-4 spikelets, 
terminal on short foliage-bearing lateral branchlets; pedicels 1.0-4.5 mm. long, smooth. 
Spikelets 7.7-10.5 mm. long; glumes vestigial, the first ca. 0.2 mm. long, the second 
0.3-0.5 mm. long; remainder of spikelet disarticulating above the glumes and falling as a 
unit; sterile lemmas 2, similar, faintly 1-3-nerved, glabrous or slightly puberulent at the 
base, triangular 5-6:1, the first 4.6-5.0 mm. long, the second 4.9-6.2 mm. long; fertile 
lemma 8.0-9.7 mm. long, faintly 5-7-nerved, ca. 3 x longer than wide, acute; palea 
similar, slightly longer, faintly 5-nerved, not grooved, bidentate; lodicules 3, ciliate 
above the middle, acute; anthers 3; style 1; stigmas 2. 

None of our Costa Rican specimens is flowering, and the spikelet 
description has been taken largely from Shattuck 71 7, from the Canal 
Zone. Munro gives an excellent plate showing flowering material (Tab. 
II). The following vegetative specimens are from Costa Rica: Prov. 
San Jose, Quizarra, Los Cusingos, elevation 760 m., Pohl & Lucas 
13114, same site, Pohl & Pinette 13257, same site, A. Skutch s.n.; 18 
km. SW of San Isidro, elevation 800 m., J. P. Smith 3000; 10 km. SW 
of San Isidro, elevation 800 m., Pohl & Calderdn 10061; 10 km. SW of 
Santiago de Puriscal, elevation 800 m., Pohl & Pinette 13286; Prov. 
Alajuela, Rio Zapote, 6 km. S of Upala, elevation 60 m., Pohl & 
Pinette 13229; Prov. Puntarenas, 2 km. NW of Guacimo, Goto Brus, 
elevation 350 m., Pohl & Pinette 13272. 

Plants of this species are scrambling vines that clamber over and 
cover small trees and canyon walls. The colony on the Puriscal Road 
(13286) is particularly conspicuous, covering the lower parts of a small 
canyon. 

Ghusquea tonduzii Hackel, Oesterr. Bot. Z. 53:155. 1903. Figure 
43. 

Caespitose bamboo in large clumps; rhizomes at least in part leptomorphous, possibly 
from the burial of culms; culms 5-20 m. long, arching, the upper ends drooping; inter- 
nodes 1-3 cm. thick, solid, cylindrical, glabrous or appressed-puberulent; nodes en- 
larged, with an evident sheath girdle and supranodal ridge; lower nodes sometimes with 
a ring of thin drooping roots; foliage-bearing branches numerous in dense fascicles, 
individual branches up to 90 cm. long; primary branch bud apparently not developing, 




FIG. 43. Chusquea species. C. tonduzii: A, spikelet; B, inflorescence; C. virgata: C, 
inflorescence. 



139 



140 FIELDIANA: BOTANY 

the branches all of equal size; foliage leaves with sheaths glabrous except for the ciliolate 
overlapping margin; external ligule evident, cartilaginous; internal ligule stiff, mem- 
branaceous, mostly 2-5 (9) mm. long, decurrent on the sheath margins; pseudopetioles 
1-3 mm. long; leaf blades flat, 9-19 cm. long, 9-18 mm. wide, ovate 10-14:1, olivaceous or 
yellowish green, the upper surface glabrous, the lower appressed-pubescent with fine 
hairs or glabrous, tessellate. Inflorescences terminal on foliage-bearing branches; 
peduncles included or exserted up to 15 cm.; panicles ovoid 2-5:1, mostly 11-19 cm. long, 
3-8 cm. wide, the branches mostly solitary or paired, one long and one short, strongly 
spreading at maturity, the longest branch 3-6 cm. long; spikelets and peduncles purple; 
peduncles, branches, and pedicels appressed puberulent, the hairs often retrorse; 
spikelets clustered along the branches, the pedicels short, 0.5-4.0 mm. long, stiff, ap- 
pressed. Spikelets purple, subcylindrical, sometimes arcuate, acute to acuminate, 6-7 
mm. long, firm-textured, glabrous except for minute ciliation on the upper margins of 
some of the bracts; glumes much reduced, rounded to barely acute at the apex, nerve- 
less, the first 0.3-1.0 mm. long, the second similar, 0.3-1.1 mm. long; disarticulation 
above the glumes, the remainder of the spikelet falling as a unit; lower 2 lemmas sterile, 
lacking paleas, the first 3-4 mm. long, narrowly ovate, acuminate or awn-tipped, 3- 
nerved; second sterile lemma similar but longer, 3.8-5.0 mm. long, broader than the 
first, acuminate or awn-tipped, 3-, 5-, or 6-nerved; terminal (fertile) floret with a some- 
what dorsally flattened lemma, 5.6-6.6 mm. long, acuminate, 5-7-nerved, its lower mar- 
gins enveloping the base of the palea; palea as long as the lemma or longer (up to 6.8 mm. 
long), broad, enwrapping the flower, rigidly bidentate at the tip, 4-7-nerved; lodicules 3, 
flat, vasculated, spatulate, the tip with a few short barbs at the tip; anthers 3, yellow, 
2.6-3.8 mm. long; ovary with a short style and 2 plumose stigmas. Caryopses not seen on 
our blooming specimens, but we have found seedlings associated with two blooming 
colonies, some of them bearing attached spikelet parts. Chromosome number n = 20 
from specimens from Poas and Turrialba. 

This species is common or abundant on the Cordillera de Talamanca, 
large colonies occurring along the CIA at elevations of 2,400-3,140 m., 
below the paramo. Gregarious blooming occurred in some colonies in 
this area in 1966, 1967, and 1968. I have not seen recent bloom (1973- 
1976) in the same region. Colonies on Volcan Turrialba, east of 
Hacienda Central, were in massive bloom in 1966 and 1968. The plants 
die after gregarious flowering. Seedlings were found growing on moss 
polsters in shade, but not on bare soil or in full sun. Except for their 
bladeless lower sheaths and pseudopetiolate leaf blades, they resemble 
other sterile grass seedlings and might easily be missed. The type 
locality of C. tonduzii is the summit of Volcan Poas, and a large popu- 
lation of the species occurs there. Blooming plants were collected there 
in 1964, 1967, 1968, and 1972. 1 have not seen recent bloom in the area. 
No specimens are recorded from Barba or Irazii, but the species should 
be sought there. Chuxquea tonduzii is not known outside of Costa 
Rica. 

Chusquea virgata Hack. , Oesterr. Bot. Z. 53:156-57. 1903. Figure 
43. 



BURGER: FLORA COSTARICENSIS 141 

Caespitose bamboo in small clumps, the few culms arising from short, pachymorphous 
rhizomes; culms solid, weak, less than 1 cm. thick (but bases recorded as up to 2 cm.), 
recorded as being up to 6-7 m. long; scrambling into brush and trees, the ends drooping; 
internodes cylindrical, glabrous, green or marbled with purple, solid; nodes swollen, 
with evident sheath girdle and supranodal ridge; primary culm sheath (one example 
seen) 9.5 cm. long, 25 mm. wide, the apex abruptly rounded to the base of an erect 
acuminate vestigial blade, ca. 1 cm. long; ligule an erose membrane ca. 1.5 mm. long; 
outer surface of sheath strongly and closely ridged, glabrous, purplish; inside surface 
tessellate-veined. Primary branch bud subtended by a row of flattened buds of minor 
branches; minor branches few, usually ca. 5 per node, up to 50 cm. long, with a few 
leaves borne toward their tips; primary branch bud sometimes not developing into a 
branch; when a primary branch is present, it is only slightly larger than the minor 
branches; sheaths of foliage leaves glabrous; external ligule evident, ca. 0.5 mm. long, 
sometimes ciliolate; internal ligule membranous, ca. 1 mm. long; pseudopetioles flat- 
tened, 1-3 mm. long; leaf blades ovate 3.2-5.2:1, rather abruptly acuminate, 7.5-17 cm. 
long, 16-33 mm. wide, flat, green on both surfaces, glabrous except for a line of short, 
stiff tan hairs on each side of the midrib just above the base of the blade. Inflorescence a 
slender virgate panicle, its base mostly included in the uppermost sheath, 9-17 cm. long, 
1.0-1.5 cm. wide, the slender appressed branches up to 3 cm. long; pedicels slender, 
erect, longer than the spikelets, which are set at an angle of ca. 30 to the pedicel. 
Spikelets linear, falcate, 8.0-9.7 mm. long; glumes very reduced, semicircular, nerve- 
less, their margins overlapping, the first 0.2-0.3 mm. long, the second 0.3-0.5 mm. long; 
disarticulation above the glumes, the remainder of the spikelet falling as a unit; lower 
two florets sterile, represented by 2 empty sterile lemmas, their tips diverging from the 
fertile lemma; first empty lemma 2.8-3.2 mm. long, ca. 2.5 x longer than wide, acute; 
second empty lemma 3.4-4.2 mm. long, acuminate; both empty lemmas 1-nerved or 
faintly 2-3-nerved; third lemma fertile, linear, subcylindrical, arcuate, acute, its margins 
covering the palea; surface glabrous; nerves 7, faint; palea as long as the lemma, broadly 
winged, rounded to the keels, 4-nerved, a deep groove between the keels; rachilla not 
prolonged behind the palea; lodicules 3, flat, vasculated, broadly spatulate, the tips 
densely ciliate with long hairs; anther (only 1 seen) 4.5 mm. long; style 1; stigmas 2, no 
caryopses seen. 

This species is apparently endemic to Costa Rica. The type, Tonduz 
7730, was collected in forests at San Marcos, at an elevation of 1,350 m. 
The specimen, collected in 1893, was in bloom. The species is widely 
distributed in central Costa Rica, but appears to be rare. Other 
blooming specimens were collected from Tarrazu in 1918, La Pena de 
Zarcero (1938), Tapesco (1940), Rio Segundo, Barba (1941), Tapesco 
(1965), and Frailes (1965). No more recent flowering specimens are 
known, but we have recently collected vegetative plants from Rio 
Birris near Pacayas. The culms are slender and delicate, and the plants 
support themselves by clambering in brush and trees. 

OTHER NOTABLE CHUSQUEA POPULATIONS IN COSTA RICA 

The abundance and complexity of the Chusquea populations in Costa 
Rica make it impossible to identify and classify them all. The popula- 



142 FIELDIANA: BOTANY 

tions on the following list have been observed, either in vegetative or 
blooming condition, but cannot as yet be assigned to definite taxonomic 
status. Continued observation may make it possible to resolve their 
status, particularly if blooming specimens can be obtained. 

1. Tapanti population. Large, coarse bamboos with drooping culms 
to 15 m. long; internodes, main-culm sheaths, and sheaths of lateral 
branches hispid with irritating hairs. The following vegetative popula- 
tions are known: Monteverde, Pohl & Pinette 13246; Alto de Roble, 
Pohl & Lucas 12998; Rio Grande de Orosi, near tunnel portal, Pohl & 
Selva 12886; Volcan Barba, W. E. Booth 161. 

2. Cariblanco population. This striking species grows on the cliff 
above the Rio Cariblanco, just east of the highway to Puerto Viejo. It 
bloomed in 1968, and most of the colony subsequently died. The plants 
are exceptionally large, the solid culms reaching a length of 20 m. , with 
long-decumbent bases. Branching is restricted, with usually 2 equal 
branches at each node. Sheaths and internodes are scabrous. The 
ovate, cordate-based blades are exceptionally large for a species of 
Chusquea, 20-37 cm. long and up to 45 mm. wide. The inflorescence is a 
slender virgate panicle up to 50 cm. long, less than 2 cm. thick. The 
spikelets are more or less typical of those of Chusquea, but the glumes 
are better developed. In general appearance, it resembles C. lan- 
ceolata Hitchc. of Guatemala, but differs in branching pattern, 
inflorescence structure, and details of spikelets and foliage. Lodicules 
3, similar to those of other Chusquea species. P. & D. 11023, 11033, 
11176, 11267, and Pohl & Pinette 13224 are representative of this 
entity. 

Because of the unusual branching pattern exhibited by these plants, 
Dr. Soderstrom believes that they may represent a new undescribed 
genus. 

3. Tarrazu population. This species occurs abundantly in and on the 
margins of the forest above the new road on the south side of the Rio 
Tarrazu, southeast of Frailes, at about 1,600 m. elevation. In January 
1975, the plants were seedlings in small clumps, but dead plants were 
not observed. By June 1976, the plants were much larger, with culms 
up to 1 cm. thick and 3 m. long. The foliage-bearing branchlets were up 
to 15 per node, and up to 35 cm. long, bearing 7-8 very slender leaf 
blades at the tip. The leaf blades are linear, flat, 14-16 cm. long, the 
length ca. 20 times the width, and bear a woolly patch on one side of 
the midrib on the abaxial side at the base. The deciduous culm sheaths 
are purple, glabrous, and rounded to a rudimentary blade. Pohl & 
Lucas 13143 and Pohl & Pinette 13211 are representative. 



BURGER: FLORA COSTARICENSIS 143 

CINNA Linnaeus 

Caespitose perennials; inflorescence a panicle; spikelets laterally compressed, 1- 
flowered, disarticulating below the glumes; glumes equal, 3-nerved, longer than the 
floret; lemma usually short-awned from just below the tip, faintly nerved; keels of palea 
very close together, the minute abortive rachilla segment partially hidden in the groove 
between them. (Pooideae: Agrostideae.) 

Cinna poaeformis (H.B.K.) Scribn. & Merr., U.S.D.A. Div. 
Agrost. Bull. 24:21. 1901. Deyeuxia poaeformis H.B.K. , Nov. Gen. & 
Sp. 1:146. 1816. Figure 44. 

Tall, succulent perennial, forming dense clumps; culms erect, 90-150 cm. tall, un- 
branched, 3-6 mm. thick, hollow, ridged, glabrous; nodes dark colored, contracted; 
leaves numerous, the basal ones bladeless; leaf sheaths mostly overlapping, glabrous, 
ridged, often purplish; ligules 1.5-15.0 mm. long, the upper ones much longer than the 
lower, brownish or purplish, membranaceous, lacerate; leaf blades flat, 5-35 cm. long, 
5-15 mm. wide, glabrous. Peduncle up to 20 cm. long, glabrous; panicles solitary, termi- 
nal, lax, 15-45 cm. long, often nodding, very open, the long branches naked, spikelet- 
bearing only near the tips, borne in verticils; spikelets borne in dense clusters near the 
tips of the branches, mostly short-pedicellate, the branches and pedicels scabrous. 
Spikelets strongly laterally compressed, the glumes keeled, equal, 3-nerved, 2.5-3.2 
mm. long, lanceolate as folded, scabrous on keel, nerves, and sometimes internerves; 
floret 1; lemma narrowly ovate, faintly (5?)-nerved, glabrous or scabrid near the tip, 
usually awnless or with a short straight awn, up to 0.3 mm. long, attached just below the 
tip; palea nearly as long as the lemma, broad, the 2 keels very close together, the minute 
rachilla segment held in the groove, ca. 0.3 mm. long; anthers 3, ca. 1 mm. long, tan. 
Chromosome number n = 14 from a Costa Rica specimen. 

Brushy or forested moist slopes; paramos, 2,800-3,400 m. elevation; 
Irazii, Asuncion, Buena Vista, Chirripo. Blooming apparently year- 
long. Mexico to Colombia, Venezuela, and Peru. 



COELORACHIS Brongniart 

REFERENCE: W. D. Clayton, Coelorachis and Rhytachne: A study in 
numerical taxonomy, Kew Bull. 24:309-314. 1970. 

Caespitose perennial grasses, the stems branched above and bearing terminal and 
axillary cylindrical rames, one on each peduncle. Spikelets paired, awnless, one sessile 
and one pedicellate, both fitting closely against the rachis; rames disarticulating at 
maturity into individual internodes, each with an attached spikelet pair; rachis inter- 
nodes thick, cylindrical, hollow, slightly widened upward, truncate; base of internode 
with a short rounded projection that fits into the hollow apex of the internode below. 
Spikelets dorsally compressed. Sessile spikelets: First glume coriaceous, elliptic-oblong, 
flattened, ca. 6-nerved, broadly winged on the upper margins and deeply notched at the 
midline; inner surface of the glume bearing 2 narrow flanges that converge toward the 
apical notch and clasp the margins of the second glume; second glume shorter and 
narrower than the first, narrowly ovate, acute, keeled, 3-nerved; lower (sterile) lemma 
nearly as long as the first glume, nerveless, hyaline, ovate; lemma of upper (fertile) floret 






FIG. 44. Cinna poaeformis. A, spikelet; B, floret with rachilla; C, panicle. 

144 



BURGER: FLORA COSTARICENSIS 145 

keeled, 3-nerved, stiffish, its palea nearly as long; lodicules 2, truncate; anthers 3; style 
branches naked at the base. Pedicellate spikelets: Similar to the sessile ones but smaller; 
pedicels thick, dorsally flattened, as long as the rachis joint or longer and fitting closely 
against it; first glume similar to that of the sessile spikelet; second glume 3-nerved, more 
strongly keeled than that of the sessile spikelet; winged at the tip, sterile lemma, fertile 
lemma and its palea well-developed; lodicules 2; anthers 3; stigmas well-developed. 

Coelorachis is distributed widely in warmer parts of both eastern 
and western hemispheres. The genus is most closely related to 
Rhytachne, Rottboellia, and Eremochloa. Our species have usually 
been assigned to the genus Manisuris. (Panicoideae: Andropogoneae.) 

KEY TO SPECIES OF Coelorachis 

la. Axillary inflorescences arising singly from each upper leaf sheath; rames up to 5 
mm. thick; rachis internodes at least 3.5 mm. long C. ramosa 

Ib. Axillary inflorescences several from each upper leaf sheath; rames less than 2 mm. 
thick; rachis internodes less than 3 mm. long C. aurita 

Coelorachis aurita (Steud.) A. Camus, Ann. Soc. Linn. Lyon 
68:197. 1922. Rottboellia aurita Steud., Syn. PI. Glum. 1:361. 1854. 
Manisuris aurita (Steud.) Kuntze, Rev. Gen. PI. 3:356. 1898. Figure 
45. 

Perennial, caespitose in dense clumps; culms erect, 100-250 cm. tall, branching from 
the middle and upper nodes; internodes glabrous, grooved on side toward the branch, 3-7 
mm. thick, mostly solid and filled with pith; nodes dark, contracted; prophylla concealed, 
3-7 cm. long; foliage clustered toward the base of the culms; sheaths glabrous, the lower 
ones overlapping, keeled, the upper shorter than the internodes; lower leaf blades elon- 
gated, keeled and mostly folded, up to 5 mm. wide, the upper much shorter; ligule a 
ciliolate membrane, 0.6-0.7 mm. long. Peduncles numerous, terminal and axillary, sev- 
eral of different lengths arising from one leaf axil, mostly included in bladeless sheaths; 
rame solitary on each peduncle, 4-9 cm. long, narrowly cylindrical, 1.5-2.0 mm. thick. 
Sessile spikelets: First glume 3.7-4.7 mm. long, oblong, rounded on the back, faintly 
pitted in rows between the 5-6 rather faint nerves; the margins winged, especially near 
the truncate, 2-lobed apex; second glume keeled, boat-shaped, 3-nerved, scabrid on the 
keel, 2.9-3.8 mm. long; lower (sterile) lemma 2.5-3.1 mm. long, ovate, acute, thin and 
nerveless; upper (fertile) lemma 2.3-2.8 mm. long, ovate, acute, slightly keeled, nerve- 
less; palea 1.9-2.5 mm. long, truncate, nerveless; anthers 3, purple, 0.8-1.5 mm. long. 
Rachis internodes and pedicels thick, the internode 2.0-2.7 mm. long, the pedicel similar 
but longer, and with a thin triangular wing at the apex on the side away from the sessile 
spikelet. Pedicellate spikelets: Similar to the sessile ones, but tending to be slightly 
asymmetric, 2.3-4.3 mm. long; first glume 3-5-nerved; second glume 2.4-4.0 mm. long, 
1-3-nerved, ovate, acute, keeled; lower lemma 1.8-3.0 mm. long; upper lemma 1.8-2.3 
mm. long; palea ca. 1.5 mm. long; flower present in our specimens, with 3 anthers and 
ovary with 2 stigmas. Chromosome number n = 9 from a Costa Rican specimen. 

This species is known in Costa Rica only from Canas Gordas, where 
it was collected by Pittier. We found it also in the same locality, grow- 
ing in a marsh in a large sinkhole between Canas Gordas and Agua 




FIG. 45. Coelorachis species. C. aurita: A, inflorescence; B, a spikelet pair, two views; 
C, culm base; C. ramosa: D, spikelet pair, two views. 



146 



BURGER: FLORA COSTARICENSIS 147 

Buena. July to October. Honduras, Costa Rica and Panama to Bolivia 
and Argentina. 

Coelorachis ramosa (Fourn.) Nash, N. Amer. Fl. 17:86. 1909. 
Apogonia ramosa Fourn., Mex. PL 11:63. 1881. Rottboellia aurita ssp. 
stigmosa Hack, in DC., Monogr. Phan. 6:311. 1889. Manisuris ramosa 
(Fourn.) Hitchc., Proc. Biol. Soc. Wash. 40:88. 1927. 

Densely caespitose perennial; culms 75-125 cm. tall, 1-3 mm. thick, solid, pithy, gla- 
brous, erect, branching from the middle and upper nodes; prophylla prominent, up to 10 
cm. long; nodes dark, constricted; herbage and stems often purplish; sheaths shorter 
than the internodes, keeled, glabrous; ligule a minutely ciliolate membrane, 0.5-1.0 mm. 
long; lower blades crowded, up to 60 cm. long and 7 mm. wide; upper blades much 
smaller. Inflorescences terminal and axillary from the upper culm nodes, the terminal 
one 7-13 cm. long and ca. 5 mm. thick, the axillary ones shorter; rame solitary, cylindri- 
cal, the spikelets and rachis internodes fitting closely together; rachis internodes thick, 
hollow, striate on the outer surface, 3.5-4.5 mm. long. Sessile spikelet 4.0-5.5 mm. long; 
first glume elliptic-oblong, coriaceous, ca. 6-nerved, slightly convex on the back, the 
marginal wings broadened toward the apex and deeply notched at the midrib, often 
purplish; back of the glume with rows of shallow pits between the nerves; second glume 
3.5-4.5 mm. long, keeled, boat-shaped, 3-nerved; lower (sterile) lemma 3.0-4.0 mm. long, 
ovate, acute, nerveless; upper (fertile) floret with an ovate, acute, nerveless lemma 
3.0-3.5 mm. long; palea 2.5-3.4 mm. long, nerveless; anthers 3, ca. 1.2 mm. long, purple. 
Pedicels thick, appressed to the rachis, with a thin triangular wing on the side of the 
apex away from the sessile spikelet; pedicellate spikelets similar to the sessile ones but 
shorter, 3.5-4.5 mm. long, tending to be more asymmetric than the sessile ones; sterile 
lemma and fertile lemma 2.4-2.7 mm. long; palea ca. 2.0 mm. long; anthers 3, 1.1 mm. 
long; some spikelets with well-developed stamens and pistil, others sterile and empty. 

Mexico to Honduras; Colombia. Not yet found in Costa Rica. 

COIX Linnaeus 

Tall, caespitose, maize-like plants; duration indefinite in the tropics; culms freely 
branching, bearing from the upper leaf axils numerous slender peduncles, each bearing 
at its apex a rigid, bony bead that is deciduous at maturity. Spikelets unisexual; pistillate 
spikelet solitary, borne within the cavity of the bead, along with two slender, tubular 
sterile spikelets. Peduncle passing through the bead and emerging through the apical 
ostiole and bearing at its apex several groups of sessile or pedicellate staminate or sterile 
spikelets in somewhat irregular groupings. Pistillate spikelet gibbous, with a slender 
beak; first glume, second glume, lower (sterile) lemma, fertile lemma and palea present; 
stigmas 2, protruding from the mouth of the ostiole at anthesis. Staminate spikelets 
herbaceous, with two equal glumes concealing the staminate florets; staminate inflores- 
cence deciduous from the bead at maturity; beads deciduous from the apex of the pedun- 
cle; caryopsis germinating while confined within the bead. 

Coix is a genus of one to several species native to tropical southeast- 
ern Asia, but widely cultivated for the beads, and sometimes for forage 
or grain. The genus has no close relationship to any native American 
genera. (Panicoideae: Andropogoneae.) 



148 FIELDIANA: BOTANY 

Coix lacryma-jobi L., Sp. PI. 972. 1753. Figure 46. 

Duration indefinite; plants 1-3 m. tall, profusely branching above; peduncles flat, 
slender, produced in clusters from the axils of the upper leaves; a hard, bony involucre 
(modified leaf) borne at the tip of each peduncle. Involucres usually subspherical, 6-8 
mm. wide, usually very hard, gray or white, shining. Pistillate spikelet one in each 
involucre, broadly ovoid, filling nearly the entire cavity, with a pronounced apical beak; 
first and second glumes about equally long, the first enfolding all but the keel of the 
second, both fleshy and delicate, almost nerveless; sterile lemma, fertile lemma and its 
palea membranaceous, delicate; lodicules none; 1-3 small rudimentary stamens present 
near the base of the ovary; stigmas 2, exserted through the ostiole of the bead; 2 sterile 
tubular rudimentary spikelets also included in the bead, lying parallel along the keel of 
the second glume and just protruding from the ostiole of the bead. Staminate inflores- 
cence borne on a flattened slender peduncle arising from the base of the bead and passing 
up through the ostiole, parallel to the rudimentary spikelets, and slightly exserted; 
staminate inflorescence usually 3-8 cm. long, composed of a varying number of triads of 
staminate spikelets, each triad of 1 pedicellate and 2 sessile spikelets; staminate 
spikelets soft-textured, with a blunt first glume, 7-12 mm. long, somewhat winged near 
the apex, flattened and with 2 lateral flanges which clasp the edges of the boat-shaped, 
ovate, acute second glume; florets 2, the upper slightly larger than the lower, both 
slightly shorter than the glumes; lemmas many-nerved, narrowly ovate, acute, glabrous; 
paleas slightly shorter than the lemmas; anthers 3, yellow, 3-5 mm. long. Chromosome 
number n - 10 from Costa Rican specimens. 

Blooming yearlong in moist habitats, possibly seasonal elsewhere. 
Low and medium altitudes, on both Pacific and Caribbean slopes. 

The hard gray or white beads that contain the pistillate spikelets are 
frequently used in making necklaces and as rosary beads. Certain 
strains of this species, which have soft beads, are sometimes used as a 
source of grain under the common name ofTrigo adlay. Common name 
of the ordinary strains isLagrimas de San Pedro, or in English, "Job's 
tears." 

CORTADERIA Stapf 

REFERENCES: H. J. Conert, Die Systematik und Anatomic der 
Arundineae, pp. 1-208. J. Cramer. Weinheim. 1961. H. E. Conner, 
Breeding systems in New Zealand grasses. V. Naturalized species of 
Cortaderia, New Zealand J. Bot. 3:17-23. 1965. 

Tall, vigorous dioecious perennial grasses, forming large dense clumps. Panicles large, 
plumy because of the numerous long silky hairs borne on the lemmas. Spikelets laterally 
compressed, wedge-shaped; florets 2-9, all alike or the uppermost much reduced and 
sterile; disarticulation above the glumes and near the base of each rachilla segment, the 
rachilla forming a stipe or callus below the detached floret; glumes subequal, 1-nerved, 
linear-lanceolate, with usually excurrent midrib, pointed or slightly rounded or bifid at 
the apex, translucent to light brown or purplish, nearly as long as the entire spikelet; 
lemmas green, purplish, or whitish and translucent, little shorter than the spikelet, 




FIG. 46. Coix lacryma-jobi. Inflorescence, showing beads and protruding staminate 
inflorescences. 



149 



150 FIELDIANA: BOTANY 

3-5-nerved or sometimes 7-nerved at the base, either linear-lanceolate, with a long 
narrow tapering apex terminating in an awn, or short and ovate, with a deeply bifid apex 
terminating in 2 awned lateral teeth, the awn flat and somewhat twisted, arising from 
the cleft between the teeth; backs of the papery lemmas bearing numerous long, silky, 
white hairs 3-10 mm. long on the lower third (staminate spikelets less hairy), midnerve 
of lemmas always continuous to the tip, the lateral nerves usually extending to the upper 
third; palea one- third to one-half as long as undivided lemmas, or reaching as far as the 
insertion of the awn in cleft lemmas, 2-nerved, truncate or 2-toothed, hairy or scabrid 
between the nerves, sometimes long-hairy on the margins; callus or stipe of the florets 
bearded with short silky hairs; lodicules 2, wedge-shaped, flat, ciliate at the tip; pistillate 
flowers with 2 terminal styles naked at their bases, their stigmas spreading laterally 
from the floret; pistillate flowers with sterile staminodes; staminate flowers with 3 large 
anthers and rudimentary ovary. 

Measurements quoted are taken from Costa Rican specimens and 
may not agree entirely with those given by Conert. The genus is 
closely related to Gynerium, Arundo, and Phragmites. Species about 
20, in Central and South America and New Zealand. (Arundinoideae: 
Arundineae.) 

KEY TO SPECIES OF Cortaderia 

la. Lemma deeply bifid at the apex, awn arising between conspicuous, awned lateral 

teeth 3.0-4.5 mm. long C. haplotricha 

Ib. Lemma tapering gradually into awn; lateral teeth of awn minute or absent 2 

2a. Panicles silvery white, very plumy, hairs of lemmas 8-10 mm. long; florets 8-9; 
pistillate flowers lacking rudimentary stamens; cultivated ornamentals 

C. selloana 

2b. Panicles brownish or purplish; hairs of the lemmas usually 3-5 mm. long; florets 
2-3; pistillate flowers with rudimentary stamens; wild plants of paramos at high 
elevations C. bifida 

Cortaderia bifida Pilger, Bot. Jahrb. 37:374. 1906. Figure 47. 

Tall, stout perennial; culms erect, to 250 cm. tall; clumps large, with very numerous 
arching basal blades; basal sheaths often closely overlapping, chartaceous, inflated, cari- 
nate, persistent, finally breaking down into curly fibers, glabrous, the margins mem- 
branous; ligule a dense row of silky white hairs, 1.5-2.0 mm. long; blades firm, to 1 m. 
long, 4-7 mm. wide, glabrous beneath, upper surface above the ligule appressed-hairy or 
glabrous, margins silky-ciliate near the base, strongly scabrous toward the tip. Panicles 
solitary, terminal, 25-35 cm. long, rather narrow, 6-20 cm. wide, dense to quite loose and 
open. Spikelets laterally compressed, wedge-shaped, 10-13 mm. long; first glume 8.0- 
11.5 mm. long, narrowly lanceolate; second glume 9.5-11.0 mm. long, narrowly lance- 
olate; florets usually 2-3, disarticulating with a bearded rachilla stipe up to 1 mm. long 
below the lemma; lemmas ca. 8 mm. long, narrowly ovate, 3-nerved, sometimes with a 
very faint additional pair near the base; apical teeth minute or absent; awn 4-8 mm. long; 
lower third of lemma bearing white, silky hairs 4-5.5 mm. long, the keels scabrous; 
flowers of our specimens functionally pistillate, with sterile abortive anthers. The Costa 
Rican specimens have developing caryopses. 

Conert (1961) reported only the type specimen of this species from 




FIG. 47. Cortaderia species. C. haplotricha: A, spikelet and a single floret; C. sel- 
loana: B, spikelet; C. bifida: C, spikelet. 



151 



152 FIELDIANA: BOTANY 

Peru. This specimen was pistillate, and no staminate plants were 
known to him. We have never seen staminate plants of C. bifida or C. 
haplotricha in Costa Rica, although we have searched for them. Quite 
probably, these species are apomictic. Conner (1965) has reported the 
occurrence of apomixis in the South American species, C. atacamen- 
sis. Conert has identified our specimens, and his determinations have 
been followed, although our plants differ in some minor respects from 
his descriptions, which are based upon South American material. Such 
differences might be expected in apomictic species. 

Cortaderia bifida has not previously been reported from Central 
America. It is rare to occasional, occurring on the upper cinder slopes 
of Irazu and Turrialba and on paramos of the Cerro de la Muerte and 
Cerro Chirripo, at elevations from 2,500 to 3,300 m. April to Sep- 
tember. 

Cortaderia haplotricha (Pilger) Conert, Systematik und Anatomic 
der Arundineae 102. 1961. Danthonia haplotricha Pilger, Bot. Jahrb. 
25:715. 1898. Figure 47. 

Caespitose perennial, forming large tussocks; up to 1 m. tall; culms ca. 5 mm. thick, 
hollow, thick-walled; nodes glabrous, not prominent; basal leaves numerous, stiffly erect; 
sheaths mostly overlapping, silky-hairy on upper margins, slightly so below the collar, 
breaking down into curly fibers when old; blades up to 80 cm. long, 4-5 mm. wide, 
glabrous below, scabrous on the margins, upper surface and margins densely silky for 
1-2 cm. above the ligule; ligule a dense row of silky hairs, 0.5-1 mm. long; peduncle 
included on our specimens; panicle up to 30 cm. long, often purplish; spikelets laterally 
compressed, V-shaped; glumes narrowly lanceolate, acuminate, purplish, 1-nerved, 13- 
13.5 mm. long; florets 4-5; lemmas 8-10 mm. long, including the bearded basal rachilla 
stipe, narrowly ovate, 7-nerved, the apex 2-cleft, the lateral teeth 3-4.5 mm. long, 
tapering into short awns; awn inserted between the teeth, flat, twisted, geniculate, 9-12 
mm. long; lower third of the lemma bearing numerous long silky hairs 4 mm. long; palea 
ca. 4.5 mm. long, ciliate on the lower margins with hairs 2 mm. long; flower pistillate, 
with abortive anthers 1.2-1.5 mm. long, yellow; lodicules 0.7 mm. long, flat, spatulate. 

This species occurs on the paramos of Asuncion, Buena Vista, and 
Chirripo Grande. The plants occur scattered on the paramo, at eleva- 
tions of 3,260-3,800 m. Plants have been seen with panicles from July 
to December. Cortaderia haplotricha has not been previously re- 
corded from Central America, but was previously known from Colom- 
bia, where both pistillate and staminate plants have been collected. 
Previous publications on Central American grasses have credited C. 
nitida (H.B.K.) Pilger to Costa Rica and Panama. Conert does not 
indicate this species occurs in Central America. 

Cortaderia selloana (Schult.) Aschers. & Graebner, Syn. Mit- 



BURGER: FLORA COSTARICENSIS 153 

teleurop. Fl. 2:325. 1900. Arundo selloana Schult., Mant. Ill (Add. 
1):605. 1827. Figure 47. 

Tall, stout perennial, forming large circular clumps; basal leaves prominent, arching 
and drooping; culms up to 3 m. tall, nearly leafless on upper portions; sheaths glabrous; 
ligule a dense row of white hairs, 1.5-2 mm. long; blades 1-2 m. long, 6-10 mm. wide, 
glabrous; midrib protruding below, yellow; blades flat or folded, very scabrous on the 
margins; auricular hairs present; peduncle solid, 5-8 mm. thick; inflorescence a rather 
dense, very plumy panicle, 70 cm. or more long in well-developed plants, pyramidal, to 
25 cm. wide, shining, silvery white; branches in dense clusters. Spikelets densely 
crowded, laterally compressed, 15-25 mm. long; glumes 15-25 mm. long, lance-attenuate; 
florets 7-9; lemmas ca. 10 mm. long, narrowly lanceolate, 3-nerved, tapering gradually 
into an awn ca. 10 mm. long, without evident lateral teeth, the back bearing long hairs 
almost to the apex; hairs on lower parts of the back up to 10 mm. long; basal stipe of 
floret bearded; palea 4.5-5.5 mm. long, scabrid on the keels; flowers pistillate, without 
rudimentary stamens (in Costa Rican cultivated specimens; Conert reports staminate 
plants from South America). Chromosome number n = 36 (Conner, 1965). 

This striking South American species is sparingly cultivated for or- 
nament around San Jose. I have seen it in Curridabat and the city 
itself. 

CRYPTOCHLOA Swallen 

REFERENCE: J. R. Swallen, Cryptochloa, in Woodson and Schery, 
Contrib. Fl. Panama VI, Ann. Missouri Bot. Gard. 29:317-322. 1942. 

Caespitose perennial grasses; culms unbranched, their lower internodes elongate, the 
foliage mostly aggregated near the apex; leaves 2-ranked, the blades lying in one plane, 
forming flat terminal sprays; blades borne on short thick pseudopetioles which serve as 
pulvini, orienting the blades in a flat plane during the day and folding them face to face at 
night. Inflorescences several, few-flowered, arising from the axils of the upper leaves, 
the peduncles concealed. Spikelets unisexual, the terminal and upper ones pistillate, the 
lower ones usually staminate. Pistillate spikelets: Dorsally compressed, 1-flowered; 
glumes equal, 3-5-nerved, longer than the solitary floret; floret borne at the tip of a thick, 
hardened rachilla internode and disarticulating with it; glumes finally deciduous; lemma 
ovate, acute, dorsally compressed, rigid, faintly 5-nerved, its flat margins incurved and 
covering the edges of the palea; palea of similar texture, 2-4-nerved, equal to the lemma 
but broader, enwrapping the caryopsis; lodicules 3, flat, vasculated, truncate; style 1; 
stigmas 3, exserted at the tip of the lemma. Staminate spikelets: Borne on erect pedicels 
on lower parts of the inflorescence, few, dorsally compressed, ovate, acute; glumes 
absent; floret 1; lemma 3-5-nerved; palea about equal to the lemma, 2-nerved; lodicules 3, 
similar to those of the pistillate spikelets; stamens 3. 

A small genus of rain forest grasses of Southern Mexico and Central 
America and northern South America. Swallen, in describing the 
genus, indicated, by his interpretations of the spikelets, that he con- 
sidered it Panicoid; however, the three flat lodicules, which occasion- 
ally bear tricellular hairs, and the presence of fusoid cells in the 



154 FIELDIANA: BOTANY 

leaf cross section indicate that it is Bambusoid. (Bambusoideae: 
Olyroideae.) 

KEY TO SPECIES OF Cryptochloa 

la. Upper leaf blades 12-26 per culm, 2-2.5 cm. long, green; staminate spikelets less 
than 3 mm. long C. concinna 

Ib. Upper leaf blades usually 5-17 per culm, 5-8 cm. long, purple beneath; staminate 
spikelets 5-6 mm. long C. granulifera 



Cryptochloa concinna (Hook, f.) Swallen, Ann. Missouri Bot. 
Gard. 29:320. 1942. Olyra concinna Hook, f., Curtis Bot. Mag. 3:52, pi. 
7469. 1896. Raddia concinna (Hook, f.) Chase, Proc. Biol. Soc. Wash. 
21:185. 1908. Figure 48. 

Caespitose perennial; plants forming vase-shaped clumps, wider than tall, the culms 
20-40 cm. long, arching and spreading from a dense common center, slender and wiry, 
hollow or solid, retrorsely puberulent in a line below the opening of the sheath above; 
apex of each internode enlarged, the pulvinus contracted, retrorsely puberulent; lower 
several internodes much elongated, their leaves with short sheaths and reduced blades; 
12-30 leaves crowded on the upper portion of the culm, their sheaths overlapping, the 
blades oriented in one plane, forming a flat spray during the day, folded face to face 
during the night; sheaths puberulent on the overlapping edge, keeled near the summit; 
ligule an erect membrane, truncate, puberulent on the back, 0.2-0.8 mm. long, or the 
uppermost one to 1.5 mm.; upper leaf blades 18-25 mm. long, 6-8 mm. wide, ovate 
2.5-3:1, abruptly acuminate, flat, glabrous, the margins scabrous; pseudopetiole minute, 
the pulvinus united to the base of the leaf blade. Inflorescences several, from the ulti- 
mate leaf axils, the peduncles concealed in the sheaths. Spikelets few, racemose, the 
terminal ones pistillate, some of the lower ones staminate. Pistillate spikelets: Ovate, 
6-7:1, acuminate, 8.4-11.7 mm. long; glumes membranaceous, subequal or the first 
slightly longer than the second; compression dorsal; first glume with 3 evident nerves 
and 2 faint marginal ones; second glume similar, both deciduous after the maturity of the 
spikelet; floret 6.1-6.9 mm. long, borne on a thick, fleshy rachilla internode and decidu- 
ous with it; lemma rigid, ivory white when immature, becoming marbled when in fruit, 
outline ovate 4:1, acuminate, its margins covering the edges of the similar palea; 
lodicules 3, truncate; style 1, stigmas 2, apically exserted; caryopsis ovate 3:1, blunt, 
tan, dorsally compressed, the pericarp extremely thin and easily scaling off the seed; 
embryo ca. one-sixth as long as the grain. Staminate spikelets: Borne on slender erect 
pedicels; few, dorsally compressed, narrowly ovate, acuminate, 2.1-2.6 mm. long; 
glumes lacking; floret solitary; lemma 3-nerved; palea 2-nerved; lodicules 3, truncate, 
vasculated; anthers 3, 1.2-1.5 mm. long. Rachilla internodes of fruiting florets contain a 
liquid, oleaginous material. Chromosome number 2n = 22 from a Costa Rican specimen. 

Rare; mostly in dense undisturbed rain forests below 100 m. eleva- 
tion. Hamburg Finca; Puerto Viejo; La Selva; Rio Hondo; NE slope of 
Volcan Orosi, 400 m. elevation. Our specimens have blooming or 
fruiting dates from December, January, April, and August, and it is 
possible that the plants bloom yearlong. They are nowhere common, 




FIG. 48. Cryptochloa concinna. A, blooming plant; B, two views of pistillate spikelet; 
C, staminate spikelet; D, pistillate floret on rachilla internode. 



155 



156 FIELDIANA: BOTANY 

and usually occur in small numbers on slopes. The Rio Hondo collection 
was made in an old cacao grove. Nicaragua to Panama and Colombia. 

Cryptochloa granulifera Swallen, Ann. Missouri Bot. Gard. 29:321. 
1942. Figure 49. 

Plants perennial, densely caespitose, 33-55 cm. tall, forming vase-shaped clumps of 
numerous ascending and arching culms; lower internodes elongated, the lower 1-3 nodes 
bearing bladeless sheaths or short sheaths with reduced blades; culm internodes 
roughened or retrorsely hispidulous, purple, thick-walled with a small lumen; nodes 
conspicuously enlarged, with a constricted ring at the middle of the enlarged portion, 
retrorsely hispidulous; sheaths tight, slightly keeled near the apex, puberulent or 
granular roughened, minutely ciliate; collar hispidulous; apex of the sheaths with erect 
auricles, the stiff membranaceous ligule 4-6 mm. long, adnate to the sheath margins, 
rounded or acute at the apex, puberulent on the back; pseudopetiole thick and fleshy, ca. 
1.5 mm. long, puberulent, serving as a pulvinus to orient the blades in one plane parallel 
to the length of the stem during the day and to fold them face to face at night; blades flat, 
deep green above, purplish beneath, 5-8 cm. long, 14-24 mm. wide, ovate, 3-4:1, abruptly 
acute at the tip; usually 5-17 blades crowded near the apex of the culms, the sheaths 
overlapping; margins of adjacent blades approaching or overlapping. Inflorescences sev- 
eral, axillary from the upper leaf sheaths or terminal, the peduncles not exserted; some 
inflorescences bearing only pistillate spikelets, others with 1-several terminal pistillate 
spikelets, the lower branches bearing racemosely arranged staminate spikelets, the 
rachis and pedicels angular or flattened, scabrous on the angles. Pistillate spikelets: 
Erect at the thickened tip of the pedicel, dorsally compressed, ovate 7:1; glumes sub- 
equal or the first slightly longer, 10.5-12 mm. long, acuminate, often tapering into an 
awn up to 1.5 mm. long; first glume with 3 conspicuous nerves and 2 very faint marginal 
ones; second glume 5-nerved, the lateral pairs of nerves close to the margins; glumes 
deciduous after the fall of the floret; floret 1, supported on a thick, rigid rachilla 1.2-1.5 
mm. long and deciduous along with the rachilla; floret dorsally flattened, ovate 4:1, 
tapered to a blunt tip, rigid, shining, ivory white; lemma ovate 2:1 when flat, the margins 
incurved over the edges of the palea, flat; nerves 5, faintly visible internally; palea 
similar to the lemma, very broadly ovate 2:1, the margins strongly incurved; lodicules 3, 
flat, truncate, vasculated; style 1; stigmas 2, exserted apically; caryopsis elliptic ovate 
3:1, ca. 5 mm. long, blunt on both ends, dorsally flattened, the pericarp orange; embryo 
small, basal, a dark line running the full length of the side opposite the embryo. Stami- 
nate spikelets: Borne on 1-several lower branches or lower portions of branches of the 
inflorescence, appressed, on pedicels 1-3.5 mm. long; glumes absent; floret 1, dorsally 
compressed, triangular 10:1; lemma herbaceous, 4.8-6.0 mm. long, acuminate, 3-nerved, 
the lateral nerves near the margin; palea equal to the lemma, with 2 keel nerves and 2 
faint marginal nerves; lodicules 3, fleshy, truncate, vasculated; anthers 3, yellow, 2.4-2.6 
mm. long, filaments short, fleshy, erect. 

This species is known from Costa Rica only from the following 
specimens. The plants were abundant in moist forest remnants on 
steep slopes. Live plants from Rio Tenorio are now growing vigorously 
in the Iowa State University greenhouse and have bloomed. 
Guanacaste, Crossing of Rio Tenorio, ca. 3 km. S of Rio Naranjo, 
elevation ca. 400 m.,Pohl & Lucas 13061, 18 December 1974; Alajuela, 
9 km. by road N of Bijagua, elevation 240 m., 17 June 1976, Pohl & 




FIG. 49. Cryptockloa granulifera. A, plant; B, inflorescence with pistillate spikelets 
above, staminate spikelets at lower left; C, two views of a pistillate floret on a thickened 
rachilla internode. 



157 



158 FIELDIANA: BOTANY 

Pinette 13233. Mexico, Guatemala, and Honduras, northwestern Costa 
Rica, Panama. 

CYMBOPOGON Sprengel 

Caespitose perennial grasses; foliage aromatic (lemon-scented in ours); inflorescence a 
dense terminal compound panicle, the branches of the various orders subtended by 
bladeless sheaths; ultimate inflorescence unit a pair of rames, exserted laterally from a 
bladeless sheath; one rame sessile at the apex of the peduncle, the other short-stalked, 
the two equal; rames short, composed of several pairs of spikelets borne on a flattened, 
readily disarticulating rachis; one spikelet of each pair sessile, the other pedicellate, both 
falling together or the pedicellate one disarticulating; basal pair of spikelets in some 
rames equal, awnless, and staminate; other pairs consisting of a sessile, perfect- 
flowered, awned spikelet and a pedicellate staminate or sterile spikelet, both usually 
similar and of about equal size. Sessile spikelets: Glumes equal, ovate, coriaceous, 
covering and concealing the florets; first glume flat, laterally keeled, usually nerveless 
between the ciliate keels; upper margins sharply inflexed, covering the edges of the 
second glume; second glume boat-shaped, keeled near the apex, 1-3-nerved; lower 
lemma membranaceous, nerveless, ciliate, lacking both flower and palea; upper lemma 
narrowly triangular, membranaceous, minutely toothed at the apex, tapering toward a 
short, straight awn (scarcely exserted in our species); palea minute or lacking; lodicules 
2, truncate; stamens 3; styles 2, naked at the base; stigmas exserted laterally. Pedicel- 
late spikelets: Similar to the sessile ones, but the first glume somewhat rounded on the 
back, 5-9-nerved, of softer texture than that of the sessile spikelet; second glume 1-3- 
nerved, boat-shaped; lemma solitary, membranaceous, sterile or with 3 stamens but no 
pistil. 

Cymbopogon contains about 30 species of grasses of the tropics of 
the eastern hemisphere. Several are cultivated for their aromatic con- 
stituents. In the structure of the inflorescence, the species are close to 
Andropogon and Hyparrhenia. (Panicoideae: Andropogoneae.) Cym- 
bopogon citratus, known as Zacate de limdn or Sontol, occurs com- 
monly at low elevations in Central America, but practically never 
blooms. It can readily be recognized by its lemon odor. 



Cymbopogon citratus (DC) Stapf, Kew Bull. 1906:357. Andropogon 
citratus DC, Cat. Hort. Monspel. 78. 1813. Figure 50. 

Perennial, forming dense vegetative clumps; individual stems very short (5-10 cm.), 
ca. 1 cm. thick, solid, stiff and woody, with very short internodes, 3-6 mm. long; foliage 
in vegetative forms all basal, leaf sheaths closely overlapping, gaping with age and 
forming somewhat flattened fans, surfaces glabrous, heavily glaucous outside and inside 
with loose, powdery wax deposits; sheath auricles erect, rounded, longer than the ligule 
and adnate to its margins; ligule a stiff, erect membrane, 2.0-2.5 mm. long, minutely 
ciliolate, straight; leaf blades at first ascending, finally drooping, up to 70 cm. long and 18 
mm. wide, glabrous, light green, broadest at the middle, tapering to a narrow base; 
margins thick, white, scabrous; midrib broad, white, protruding on the abaxial surface. 
Culms usually absent, the plants essentially nonblooming. Culms up to 2 m. tall, un- 




FIG. 50. Cymbopogon citratiis. A, plant base with overlapping sheaths; B, compound 
inflorescence of numerous bracted rames. 



159 



160 FIELDIANA: BOTANY 

branched; inflorescence a large terminal panicle of rames, up to 60 cm. long and ca. 
one-third as wide, open to rather dense, complexly branched, the branches of each order 
subtended by bladeless sheaths. Ultimate inflorescence unit a pair of short, usually 
reflexed rames, exserted near the base of a bladeless sheath on a short peduncle; rames 
1.0-1.5 cm. long, one of each pair sessile, the other on a very short peduncle; spikelets 
paired, one sessile and the other pedicellate, the rame consisting of 1-4 pairs of spikelets 
and a terminal triad of one sessile and 2 pedicellate ones; disarticulation at the base of 
each rachis internode and pedicel; internodes and pedicels flattened, strongly ciliate on 
the margins. Sessile spikelets: 3.2-5.0 mm. long, ovate 3:1, acute; first glume flat on the 
back, the margins sharply inflexed and keeled, ciliate above; area between the keels 
nerveless or with 2 weak nerves near the bifid tip; second glume boat-shaped, slightly 
shorter than the first and clasped by its margins, 1-3-nerved; lower lemma membranace- 
ous, ovate, ciliate-margined, 2.8-3.2 mm. long, lacking a flower or palea; upper (fertile) 
lemma subulate, 2.0-2.5 mm. long, membranaceous, tapering into a weak awn 1-2 mm. 
long, usually straight or slightly twisted near the base; palea minute or lacking; lodicules 
2, truncate; stamens 3, the anthers yellow, 1.0-1.5 mm. long; style branches 2, naked 
near the base; stigmas purple. Pedicellate spikelets: Similar to the sessile ones but 
usually somewhat smaller, awnless; first glume slightly rounded on the back, 2.5-4.4 
mm. long, 5-9-nerved; second glume 1-nerved or faintly 3-nerved; spikelets empty or 
with the lower lemma developed, sometimes with a staminate flower, the 2-3 anthers 
yellow, 2-3 mm. long; no palea, upper lemma, or pistil observed. 

This species occurs around houses, but is apparently not cultivated 
on a commercial scale in Costa Rica. It is said that the strongly scented 
foliage is used for teas. The odor closely mimics that of lemon. Native 
to India and widespread in the tropics. Because of the lack of flower- 
ing, the plants can be spread only by cultivation. In Guatemala, "lemon 
grass" is cultivated on a large scale on the Pacific Coastal Plain for the 
production of lemon oil. A few flowering specimens are known from 
cultivation. This species bloomed in El Salvador in June 1932. A 
blooming specimen from El Zamarano, Honduras, was collected in 
November 1948, and another from Turrialba, Costa Rica, in October 
1950. We have never observed flowering. Common names: Zacate de 
limon, Sontol. 

CYNODON L. C. Richard 

REFERENCES: W. D. Clayton & J. R. Harlan, The genus Cynodon L. 
C. Rich, in tropical Africa, Kew Bull. 24:185-189. 1970. J. R. Harlan, J. 
M. J. de Wet, W. W. Huffine, & J. R. Deakin, A guide to the species of 
Cynodon (Gramineae), Oklahoma Agric. Exp. Sta. Bull. B-673:l-37. 
1970. J. M. J. de Wet & J. R. Harlan, Biosystematics of Cynodon L. C. 
Rich. (Gramineae), Taxon 19:565-569. 1970. 

Stoloniferous or rhizomatous perennials; inflorescence of 1-several whorls of slender 
spikes; spikelets sessile or nearly so in 2 rows along the lower side of the slender rachis. 
Spikelets 1-flowered, laterally, compressed and keeled; glumes narrow, 1-nerved, often 



BURGER: FLORA COSTARICENSIS 161 

arcuate, usually shorter than the floret; lemma boat-shaped, 3-nerved, the lateral nerves 
marginal; palea nearly as long as the lemma; rachilla extended behind the palea as a 
naked bristle. 

This is a small (ca. eight species) but important genus of the warmer 
regions of the Old World. Some of the species are extensively variable. 
Various species and minor variants, including hybrids, are used as 
lawn and pasture grasses. Leaves on stolons are subopposite, because 
of alternating long and short internodes of the stems. Cynodon dacty- 
lon, "Bermuda grass," is one of the most common pantropical weeds. 
(Chloridoideae: Chlorideae.) 

KEY TO SPECIES OF Cynodon 

la. Plants producing rhizomes as well as stolons; plants usually not more than 20 cm. 

tall; mostly wild plants C. dactylon 

Ib. Plants producing stolons only; plants up to 60 cm. tall; stolons thick and coarse; 

cultivated crop plant C. nlemfuensis 

Cynodon dactylon (L.) Pers., Syn. PL 85. 1805. Panicum dactylon 
L., Sp. PL 58. 1753. Figure 51. 

Perennial, spreading extensively by stolons and rhizomes; culms erect, usually less 
than 20 cm. tall; stolons with alternating long and short internodes, causing the leaves to 
appear subopposite; culms numerous, arising from the nodes of the stolons, unbranched, 
ca. 1 mm. thick, hollow but thick- walled, glabrous; nodes glabrous; prophylla short, 
broadly winged, 3-4 mm. long; foliage grayish-green; sheaths mostly glabrous, bearing 
long soft hairs on the auricles and collar; leaf blades 1-12 cm. long, 2-4 mm. wide, flat or 
folded, the tip blunt, mostly glabrous, but with long soft hairs on the basal margins of the 
blade and on the upper surface behind the ligule; ligule membranaceous, ciliolate, 0.2-0.3 
mm. long. Peduncle slender, glabrous, exserted; inflorescence solitary, terminal, a 
single whorl of usually 4-6 slender spikes, usually 1.5-3 cm. long, rarely longer. Spikelets 
overlapping, appressed to the rachis; 2.0-2.5 mm. long; glumes subequal, 1.1-1.7 mm. 
long, the first linear, arcuate, appressed to the keel of the lemma, the second straight, 
subulate, usually diverging from the floret; lemma boat-shaped, usually slightly silky on 
the keel, rarely glabrous; palea about as long as the lemma; rachilla prolonged behind the 
palea, about half as long as the floret, bearing a rudiment up to half its own length (rarely 
missing); anthers 3, yellow, 1.0-1.4 mm. long. Chromosome number usually n = 18, 
sometimes 9. 

Common, mostly as a weed or in pastures, from sea level to 1,500 m. 
elevation. Blooming yearlong. This is one of the commonest introduced 
grasses. It is variously known as "Bermuda grass," "grama," or zacate 
Bermuda. Throughout warm climates of the world, apparently 
originating in Africa. A number of varieties are listed by de Wet and 
Harlan from the Old World. 

Cynodon nlemfuensis Vanderyst, Bull. Agric. Congo Beige 13:342. 




FIG. 51. Cynodon species. C. dactylon: A, blooming plant; B, spikelet and floret with 
rachilla internode; C. nlemfuensis: C, blooming plant; D, spikelet and floret with rachilla 
internode. 



162 



BURGER: FLORA COSTARICENSIS 163 

1922. C. dactylon (L.) Pers., var. sarmentosus Parodi, Revista Ar- 
gent. Agron. 23:185. 1956. Figure 51. 

Coarse stoloniferous perennial, lacking rhizomes; culms erect from the nodes of the 
stolons, unbranched, hollow, 2 mm. thick, glabrous, 30-60 cm. tall; stolons 2-3 mm. thick, 
with alternating long and short internodes, the leaves appearing to be subopposite; 
branching extensive; prophylla prominent, 7-25 mm. long; sheaths glabrous; ligule a 
minutely ciliolate membrane, 0.3 mm. long; blades flat, 5-16 cm. long, 2-6 mm. wide, 
bearing long soft hairs on the auricles, dewlap, and base of the blade, especially behind 
the ligule; sometimes with scattered hairs on the surface, especially beneath; inflores- 
cence solitary, terminal, of 1-2 whorls of slender spikes, usually 4-9 spikes per inflores- 
cence; racemes 4-10 cm. long; spikelets 2-3 mm. long; glumes subequal, 1.8-2.3 mm. long, 
the first arcuate, linear, appressed to the keel of the lemma; second glume narrowly 
lanceolate, diverging from the floret; lemma 2.5-2.8 mm. long, boat-shaped, softly 
appressed-pubescent on the keel; palea equal to the lemma; rachilla ca. half the length of 
the palea, the rudiment minute; anthers 3, yellow, 1.2 mm. long. Chromosome number 
n = 9. 

This African species has been cultivated in the grass garden of the 
IICA at Turrialba, and is now being cultivated extensively in the Orosi 
area and in Guanacaste, as well as in other parts of Central America. 
The plants are much larger and more vigorous than the common weedy 
type of C. dactylon. It may possibly be cultivated under the name of 
Estrella africana or "African stargrass" or as C. plectostachyus. 

CYNOSURUS Linnaeus 

Inflorescence a dense terminal panicle; spikelets paired, of 2 kinds, one of each pair 
sterile and one fertile; sterile spikelets conspicuous, fan-shaped, with 2 glumes and a 
number of empty sterile lemmas borne on nondisarticulating rachilla; fertile spikelets 
similar, mostly hidden by the sterile ones, 2-5-flowered; glumes slender, 1-nerved; 
spikelets disarticulating above the glumes and between the florets; lemmas with a visible 
midrib and very inconspicuous lateral nerves, short-awned. (Pooideae: Poeae.) 

Cynosurus cristatus L., Sp. PL 72. 1753. Figure 52. 

Caespitose perennial, leafy at the base; plants 20-80 cm. tall, culms unbranched, with 
2-3 nodes, 1.0-1.5 mm. thick, hollow; sheaths much shorter than the slender glabrous 
internodes; ligules 1-1.5 mm. long, membranaceous, auriculate, decurrent on the sheath; 
blades mostly basal, 4-15 cm. long, 1.5-2.5 mm. wide, glabrous; panicles solitary, termi- 
nal, densely cylindrical, 2-8 cm. long, ca. 1 cm. wide, the branches very short and 
few-flowered; sterile spikelets fan-shaped, lustrous, mostly borne exterior to the fertile 
ones, slightly larger than the fertile spikelets; lemmas empty, 1-nerved, 3-5 mm. long; 
fertile spikelets 3-6 mm. long; glumes 3-5 mm. long, 1-nerved, narrowly lanceolate; 
lemmas 3-4 mm. long, narrowly ovate, tapering abruptly to a short awn-point, scabrous 
on the upper half; paleas 2-keeled, glabrous; anthers 3, yellow, ca. 2 mm. long. Chromo- 
some number n = 1. 

This species is known from Central America only from the following 
specimen: Cartago, pastures on south slope of Volcan Turrialba, eleva- 





FIG. 52. Cynosurus cristatus. A, sterile spikelet; B, fertile spikelet; C, inflorescence. 



164 



BURGER: FLORA COSTARICENSIS 165 

tion 2780 m., Pohl & Davidse 10865, 8 August 1968. Cynosurus cris- 
tatus is a European species, rather sparingly introduced in northeast- 
ern North America and the Pacific Coast states of the United States. 
Like Danthonia decumbens, Festuca rubra, Poa annua, P. trivialis, 
and a number of other species, it probably represents an early intro- 
duction to Costa Rica in pasture seed. Only a few plants were seen, 
and the plants have no economic utility in Costa Rica. 

DACTYLIS Linnaeus 

Tufted perennial, forming large clumps; culms erect; herbage generally glabrous, pale 
green; sheaths keeled, with united margins; ligules prominent, membranaceous, lacer- 
ate; leaf blades flat or folded; panicles simple, with few straight, stiff branches which are 
naked for most of their length and bear dense tufts of nearly sessile spikelets at their 
outer ends; spikelets strongly flattened, the glumes and lemmas strongly keeled, usually 
pectinate-ciliate on the keels; lemmas 5-nerved, tapering into a short awn-tip; disarticu- 
lation above the glumes and between the florets. (Pooideae: Poeae.) 

Dactylis glomerata L., Sp. PI. 171. 1753. Figure 53. 

Plants forming large tufts; culms up to 140 cm. tall, erect; blades 10-45 cm. long, 2-14 
mm. wide; ligules 2-12 mm. long. Panicles up to 30 cm. long, the few stiff branches 
spreading in anthesis but erect later. Spikelets 5-9 mm. long, 2-5-flowered; glumes 
lanceolate, 1-3-nerved, 4-6.5 mm. long; lemmas closely imbricated, strongly keeled, 
5-nerved, 4-7 mm. long; palea about equal to the lemma; keels of lemmas usually promi- 
nently short pectinate-ciliate. Chromosome number n = 14 from a Costa Rican speci- 
men. 

Middle and higher elevations; Irazu and Turrialba. Introduced from 
Europe as a pasture and hay grass and naturalized on the volcanoes. 
Widespread in temperate humid areas of the world, where it is culti- 
vated as a forage crop. This species is said to be used as a hay crop in 
Costa Rica, but it does not appear to be abundant at the present time. 
Common name: "orchard grass." 



DACTYLOCTENIUM Willdenow 

REFERENCE: B. E. Fisher & H. G. Schweickerdt, A critical account 
of the species of Dactyloctenium Willd. in Southern Africa, Ann. Natal 
Museum X:47-77. 1941. 

Annual or perennial caespitose or stoloniferous grasses. Inflorescence a whorl of sev- 
eral spreading or reflexed one-sided spikes, the axis prolonged as a naked point beyond 
the spikelets. Spikelets sessile, densely imbricated in 2 rows along the lower side of the 
rachis, laterally compressed and keeled; glumes 2, keeled, 1-nerved, broad, the second 
truncate, with a short, divergent awn; disarticulation between the glumes, the second 
falling with the several florets; lemmas ovate, pointed or apiculate, strongly compressed 
and keeled, 3-nerved, the midnerve prominent, green, the lateral nerves obscure, sub- 






FIG. 53. Dactylis glomerata. A, inflorescence and culm base; B, spikelet; C, base of 
blade with ligule. 



166 



BURGER: FLORA COSTARICENSIS 167 

marginal; second glume and lemmas disarticulating from the intact rachilla, the paleas 
remaining attached; palea about as long as the lemma; lodicules 2, truncate, anthers 3, 
seed broadly ovate, truncate, with strong transverse ridges; pericarp thin and delicate, 
disappearing before maturity. 

This is a small genus of ca. 10 species of warm climate grasses, 
native to Eurasia, Africa, and Australia; introduced in warm climates 
in the Americas. Dactyloctenium is closely related to Eleusine, and 
the plants are similar in habit and inflorescence structure. 
(Chloridoideae: Eragrosteae.) 

Dactyloctenium aegyptium (L.) Beauv., Ess. Nouv. Agrost. 72; PI. 
XV, Fig. 2. 1812. Cynosurus aegyptius L., Sp. PL 72. 1753. Figure 54. 

Plants annual in temperate climates, of indefinite duration in the tropics; spreading by 
short stolons and forming radiate mats, the erect portions of the culms 2-50 cm. tall; 
branching abundant on the creeping stolons, the erect culms unbranched, 1.0-1.5 mm. 
thick, glabrous, solid, the nodes with conspicuous pulvini; prophylla prominent, 10-15 
mm. long, with 2 ciliate awns up to 3 mm. long; leaf sheaths carinate, overlapping on 
short shoots, shorter than the internodes on the culms, glabrous to pustulose-villous; 
ligule a thin brownish ciliolate membrane, ca. 0.5 mm. long; leaf blades 1-7 cm. long, 1-7 
mm. wide, the uppermost much reduced; midrib prominent; blades papillose-villous on 
the margins and more or less on both surfaces, occasionally glaucous. Peduncle glabrous, 
exserted 1-10 (-20) cm. long; inflorescence a whorl of usually 2-4 unilateral spikes, 
terminal on the culm, rarely a solitary spike in depauperate plants; spikes subsessile, 1-3 
cm. long, the axis extended beyond the spikelets as a short naked point; spikelets 
densely crowded in 2 overlapping rows on the lower side of the rachis. Spikelets gray to 
purplish, strongly laterally compressed and keeled, ca. 4 mm. long; first glume 1-nerved, 
2 mm. long, ovate, apiculate; second glume similar but longer, ca. 3 mm. long, broadly 
ovate, with a short thick divergent awn; disarticulation usually above the first glume but 
not between the florets; florets usually 3, the uppermost often sterile; lemmas 2-3 mm. 
long, ovate, the keel strongly bowed; midnerve conspicuous, green, the lateral nerves 
very inconspicuous; keel scabrid; tip acuminate; palea ca. 2 mm. long, ciliolate on the 
keels; anthers 3, ca. 0.4 mm. long, yellow; pericarp very thin and fragile, soon shed, the 
rugose, angular brown seed then free. Chromosome numbers 2n = 46, 48, 45, 20, 36, 40 
(Gould & Soderstrom, 1974). 

Savannas, pastures, beaches, weedy open areas, from sea level to 
1,200 m. elevation, on both Caribbean and Pacific slopes. Blooming 
yearlong. Introduced from the Old World. Southern and eastern 
United States through the tropics to Uruguay. 

Where plants of this species grow on bare soil, they make decum- 
bent circular mats, with considerable stoloniferous spread. Extreme 
dwarfing of the plants can occur under drought or poor soil conditions, 
and such plants may often show glaucous leaves. Seeds from such 
glaucous plants, grown in the greenhouse on sand or loam soil with 
adequate moisture produced only green-leaved plants. 




FIG. 54. Dactyloctenium aegyptium. A, plant with stoloniferous base and inflores- 
cence; B, spikelet. 



168 



BURGER: FLORA COSTARICENSIS 169 

DANTHONIA Lamarck & De Candolle 
Nomen Conservandum 

Caespitose perennial grasses; inflorescence a solitary terminal panicle; spikelets 
several-flowered; glumes as long as the spikelet, equal, many-nerved; disarticulation 
above the glumes and between the florets; lemmas 5-7-nerved, awned between 2 apical 
teeth, or the apex of the lemma trifid; flowering mostly cleistogamous; axillary cleis- 
togenes also produced inside the sheaths at the lower nodes; culms disarticulating at the 
lower nodes and discharging the cleistogenes at maturity. (Arundinoideae: Dan- 
thonieae.) 

Danthonia decumbens (L.) Lam. & DC., F. Franc, ed. 3, Vol. 3:33. 
1805. Festuca decumbens L., Sp. PI. 75. 1753. Sieglingia decumbens 
(L.) Bernh., Syst. Verz. Erf. 20:44. 1800. Figure 55. 

Caespitose perennial, forming dense clumps; culms 20-50 cm. tall, erect to ascending, 
ca. 1 mm. thick, hollow, glabrous; leaf blades mostly at the base of the culms; sheaths 
more or less hairy on the upper half; innovations extravaginal; prominent auricular hairs 
present; ligule a dense circle of hairs, ca. 0.5 mm. long; blades 4-10 cm. long, 1.5-3 mm. 
wide, ribbed on both surfaces, flat or inrolled, bearing scattered long weak hairs. Pani- 
cles 2-6 cm. long, contracted, few-flowered. Spikelets almost entirely cleistogamous; 
glumes equal, 6-12 mm. long, 5-7-nerved, broadly lanceolate, rounded on the back, 
overlapping; florets 4-7; lemmas 4-6 mm. long, oval to broadly ovate, 9-nerved, rounded 
on the back, bluntly 3-toothed at the tip, smooth and shining, firm, ciliate on the lower 
margins, otherwise glabrous; callus projecting, bearing tufts of hairs ca. 1 mm. long; 
palea 4-5 mm. long, broadly ovate, the keels prominent and conspicuously thickened 
below into pulvini; rachilla segments slender, smooth, 0.6-0.7 mm. long; anthers 3, those 
of cleistogamous flowers 0.2-0.3 mm. long, those of the rare chasmogamous flowers 1-2 
mm. long; lodicules not developed; anthers remaining entangled with the stigmas and 
persisting on the tip of the fruit; caryopsis 2.0-2.5 mm. long, elliptic, flattened, with a 
terminal appendage. Basal sheaths swollen just above the nodes and containing cleis- 
togenes; the cleistogene enveloped in a prominent prophyllum ca. 10 mm. long, short- 
pedicellate, with 1 or 2 abortive glumes ca. 1-4 mm. long; florets 1 or rarely 2, 5-8 mm. 
long, the rachilla sometimes prolonged and bearing a reduced abortive floret; culms 
eventually breaking at the nodes and releasing the cleistogenes. Chromosome number 
n = 18 from Costa Rican specimens; n - 28, 36, 124 also listed by Bolkhovskikh et al. 
(1969). 

This is an introduced European species, probably imported at an 
early date in pasture seed mixtures. The only known localities from 
Central America are the following: Alajuela, Volcan Poas, 1 km. below 
crater on road; elevation 2,310 m., Pohl & Davidse 10813; Cartago, 
Volcan Turrialba, southern slope, open pastures above the lecheria, 
elevation 3,000 m., Pohl & Davidse 10858. The above two specimens 
were blooming in August. Few plants were found. Danthonia decum- 
bens is native in Europe and Asia Minor and Northwest Africa and has 
been introduced in northeastern United States and Canada and in New 
Zealand. 




B 





FIG. 55. Danthonia decumbens. A, spikelet; B, two views of a floret; C, inflorescence. 



170 



BURGER: FLORA COSTARICENSIS 171 

This peculiar cleistogamous grass has usually been assigned to the 
genus Sieglingia; however, Conert (1969) has shown that it is very 
similar in morphology and biology to the other species of Danthonia, 
differing only in the absence of a developed awn. It also forms spon- 
taneous hybrids with Danthonia alpina, a European species. For this 
reason, he assigns it to Danthonia. The generic name Sieglingia 
Bernh. (1800) antedates Danthonia by five years. Because of the 
necessity of combining the two genera, Danthonia, which has many 
species, was conserved over Sieglingia with only one. 

DESCHAMPSIA Beauvois 

Caespitose, usually perennial grasses; inflorescence a terminal panicle. Spikelets 
2-flowered; glumes subequal, keeled, longer or shorter than the florets; disarticulation 
above the glumes and between the florets; lemmas lobed at the apex; awn inserted below 
the middle of the back of the lemma; rachilla internodes short, the rachilla extended 
above the base of the second floret as a short bristle. 

This genus is allied to Trisetum, from which it differs in the basally 
attached awns, and to Aira, which lacks the prolonged rachilla. De- 
schampsia has about 35 species in cool and alpine regions of the world. 
(Pooideae: Aveneae.) 

KEY TO SPECIES OF Deschampsia 

la. Panicle open, pyramidal, the few-flowered branches naked for their lower halves 

D. flexuosa 
Ib. Panicle densely cylindrical with closely overlapping spikelets D. pringlei 

Deschampsia flexuosa (L.) Trin., Mem. Acad. Imp. Sci. Saint- 
Petersbourg, Ser. 6, Sci. Math., Seconde Pt. Sci. Nat. 4:9. 1838. Aira 
flexuosa L., Sp. PL 65. 1753. 

Caespitose perennial, in dense tufts; plants 30-85 cm. tall; foliage mostly basal, the leaf 
blades capillary, mostly 10-15 cm. long, less than 1 mm. wide, involute, glabrous; ligule a 
firm membrane, 0.5-1.5 mm. long; culms slender, the internodes very elongate. Peduncle 
elongate, exserted up to 30 cm.; inflorescence a solitary very open terminal panicle, 
pyramidal, the few branches naked for the lower one-half to two-thirds, bearing few 
spikelets, these borne on slender pedicels longer than the spikelets themselves. 
Spikelets usually purplish, 4.0-5.8 mm. long, laterally compressed; glumes shorter than 
the spikelet, rounded on the keel, 1-nerved, ovate, acuminate, the first 3.0-4.4 mm. long, 
the second 3.6-5.0 mm. long; florets close to each other, the rachilla internode very short, 
0.3-0.8 mm. long, bearded; lemmas scaberulous, lanceolate, faintly 5-nerved, bidentate 
at the acuminate tip; callus short-bearded; awn 5-7 mm. long, inserted just above the 
base of the lemma, the lower segment tightly twisted, brown, the terminal segment 
exserted from the glumes; palea about as long as the lemma, scabrous on the keels; 
anthers 3, purplish, 2.1-3.0 mm. long; caryopsis linear, rigid. 

Collected only once in Costa Rica, from a pasture on the south slope 



172 FIELDIANA: BOTANY 

of Volcan Turrialba at 3,000 m. elevation. August. This is a species of 
temperate and arctic North America and Eurasia. It has not previ- 
ously been reported from Central America. Its presence in a high 
elevation pasture along with other species of northern European origin 
suggests that it was introduced in pasture seed mixtures of European 
origin. 

Deschampsia pringlei Scribner, Proc. Acad. Nat. Sci. Philadelphia 
43:300. 1891. Figure 56. 

Caespitose perennial; plants 30-100 cm. tall, erect; culms unbranched, 1-2 mm. thick, 
hollow, thin- walled, glabrous and shining; nodes conspicuous, dark and shrunken; leaf 
sheaths shorter than the internodes, glabrous, striate; ligule a firm truncate membrane, 
1.5-2.5 (-4) mm. long; blades flat, 7-12 cm. long, 2-4 mm. wide, minutely scaberulous. 
Peduncle glabrous, exserted up to 20 cm.; panicle solitary, terminal, densely cylindrical, 
somewhat lobed below, 10-15 cm. long, 5-15 mm. thick, grayish or pinkish; spikelets 
densely overlapping on the short erect branches, the short pedicels hispidulous. 
Spikelets 4.8-5.6 mm. long, laterally compressed, the glumes subequal, keeled, 1- 
nerved, longer than the florets, the keels scabrous; first glume 4.0-4.9 mm. long, ovate, 
acuminate, the second similar, 4.2-5.6 mm. long; disarticulation above the glumes and 
between the 2 florets; lemmas 3.3-4.3 mm. long, lanceolate, faintly 5-nerved; callus 
short-bearded; apex lobed 1.0-1.5 mm., the lobes rounded or erose; awn geniculate, 
exserted, 4.5-5.0 mm. long, inserted ca. one-fourth above the base of the lemma; palea 
3.0-3.6 mm. long; rachilla internodes very short, bearded; anthers 1.2-1.3 mm. long, 
whitish; caryopsis linear-cylindrical, soft, the endosperm pasty. Chromosome number 
n = 14 from a Costa Rican specimen. 

Rare, margins of a quebrada below San Juan de Chicoa at 2,600 m. 
elevation. Previously known from southern Mexico and Guatemala. 

Deschampsia pringlei has recently been transferred to the genus 
Peyritschia by Stephen D. Koch in Taxon 28: 233, 1979. The genus 
Peyritschia differs from Deschampsia in having a soft caryopsis with 
liquid interior and basal shoots bursting through the base of the sub- 
tending sheath. The genus Peyritschia differs from Trisetum in having 
a bilobed apex on the lemma, glumes exceeding the florets and stamens 
2 per floret. 



DIECTOMIS Kunth 
Nomen Conservandum 

Caespitose; inflorescences numerous, terminal and axillary, each one a solitary rame 
or a conjugate pair of rames on a bracted peduncle; rachis disarticulating readily into 
individual segments, each bearing a dimorphic pair of spikelets; rachis internodes and 
pedicels flattened, narrowly obtriangular, with silky-ciliate edges and an obliquely cup- 
like toothed apex; sessile spikelet remaining attached to the rachis internode and 
pedicel, perfect-flowered, strongly laterally compressed; first glume narrow, 2-keeled, 
grooved between the keels, second glume strongly laterally compressed and keeled, 



B 



FIG. 56. Deachampsia pringlei. A, inflorescence; B, spikelet; C, florets. 



173 



174 FIELDIANA: BOTANY 

boat-shaped, bearing a long curved awn from the tip; sterile lemma hyaline, 2-keeled, 
narrowly lanceolate; fertile lemma hyaline, strongly keeled, the keel curved to fit the 
second glume, bearing a long exserted twisted and geniculate brown awn from between 
2 triangular teeth; palea hyaline; flower perfect; pedicellate spikelet larger than the 
sessile one, readily deciduous from the pedicel, sterile or staminate; first glume broad 
and flat, stiff, several-nerved, asymmetric, awned from the acute apex, the margins 
narrowly and sharply inflexed, the folded edge strongly scabrous or ciliate; second glume 
shorter and narrower than the first, oblong, membranaceous, bearing a short straight 
apical awn. Terminal segment of the rachis bearing one sessile and 2 pedicellate 
spikelets. 

Diectomis is a small genus of tropical grasses of both eastern and 
western hemispheres, related to Andropogon and sometimes included 
as a section of that genus. It differs in the strongly laterally com- 
pressed sessile spikelets with awned second glumes, and in the en- 
larged pedicellate spikelets. The plants are probably annual. 
(Panicoideae: Andropogoneae.) 

KEY TO SPECIES OF Diectomis 

la. Rames solitary on each peduncle D. fastigiata 

Ib. Rames paired at tip of each peduncle D. angustata 

Diectomis angustata Presl, Rel. Haenk. 1:333. 1830. Andropogon 
angustatus (Presl) Steud., Syn. PL Glum. 1:370. 1854. 

Duration indefinite; plants caespitose, erect, 20-100 cm. tall; culms branching from the 
base and the middle and upper nodes, 1.0-1.5 mm. thick, hollow or pithy, glabrous; nodes 
glabrous, not prominent; sheaths shortef than the internodes, glabrous; ligule a truncate 
brown membrane, 1.0-2.5 mm. long, adnate to the upper sheath margins; leaf blades up 
to 30 cm. long, 1.5-3.0 mm. wide, glabrous, flat; midrib wide, white. Peduncles mostly 
enclosed in slender, bladeless sheaths; inflorescences terminal, of numerous individual 
peduncles arising from upper sheaths, each bearing a conjugate pair of rames, these 2-4 
cm. long. Spikelets paired, one sessile and perfect-flowered, one pedicellate and sterile 
or staminate, both falling together with the rachis internode and pedicel when the rachis 
disarticulates; terminal sessile spikelet of each rame accompanied by 2 pedicellate ones; 
callus of sessile spikelet sharp, bearded, prolonged about 1 mm. below the insertion of 
the pedicel and rachis internode; pedicels and rachis internodes similar, ca. half as long 
as the sessile spikelet, very narrow at the base, wedge-shaped upward, slightly convex 
on the outer side, thin-walled and hollow, lower two-thirds of the edges ciliate, apex 
terminating in a very obliquely U-shaped cuplike apex, wider than the spikelet base 
above. Sessile spikelet: 4.4-5.0 mm. long; first glume deeply grooved on the back, ca. 
6-nerved, lacking a midrib, bifid at the tip; second glume longer than the first, strongly 
keeled, boat-shaped, the spikelets appearing laterally compressed; glume faintly 3- 
nerved, bearing a slender awn, 10-15 mm. long from the blunt tip; lower lemma 1- 
nerved, thin, marginally ciliate, 2-keeled, lacking a midrib, 3.0-4.2 mm. long; upper 
lemma fertile, 2.8-4.0 mm. long, hyaline, 1-nerved, the awn arising from the bifid tip; 
awn twisted and geniculate, brown, slightly hispid, 3-5 cm. long; palea nerveless, 1.5-2.0 
mm. long; lodicules 2, truncate; anthers 3, 1.7-2.1 mm. long. Pedicellate spikelets: Ovate 
6:1, acute, 5.5-6.0 mm. long, dorsally compressed; first glume slightly convex, 3-7- 



BURGER: FLORA COSTARICENSIS 175 

nerved, its margins inrolled over the edges of the second glume, ciliate above the middle; 
apex bifid, a straight awn 5-13 mm. long arising between the teeth; second glume 
rounded on the keel, 3-nerved, with an awn ca. 3 mm. long; florets absent or, in some 
cases, the spikelet with a lower lemma ca. 5 mm. long, thin and nerveless; upper lemma 
5.1-5.3 mm. long, thin and ciliate, 1-nerved; palea 2.2-3.0 mm. long; lodicules 2, truncate; 
anthers 3, 2.5-3.0 mm. long. Chromosome number n = 20 from Costa Rican specimens. 

Curatella-Byrsonima savannas, Guanacaste; elevation 100-250 m. 
October to December. Southern Mexico to Panama and Colombia, 
Venezuela, and northern Brazil. 

Diectomis fastigiata (Swartz) Beauv., Ess. Nouv. Agrost. 132, 160. 
1812. Cymbachne fastigiata (Swartz) Roberty, Mon. Androp. Boissi- 
era 9:255, 1960. Andropogonfastigiatus Swartz, Prodr. Veg. Ind. Occ. 
26. 1788. Figure 57. 

Caespitose annual; plants 30-200 cm. tall, erect; branching abundant from middle and 
upper nodes; prophylla thin, brown, up to 5 cm. long; culms slender, hollow, smooth and 
glabrous; nodes glabrous, impressed; lower leaf blades very elongate, up to 35 cm. long, 
1-3 mm. wide, tapering into an elongated awn tip, scabrous below, puberulent above, 
sometimes with scattered elongate weak hairs; upper leaves reduced to sheaths with 
awnlike reduced blades; ligule stiff, erect, brown, 2-11 mm. long, decurrent on the 
sheath margins; rames numerous, solitary or in small groups, exserted on slender 
branches from the middle and upper leaf sheaths; peduncle bearing at its base a 
spathelike sheath which includes the base of the rame, its blade reduced to an awn; an 
elongated slender prophyllum borne within the spathe; rames 3-5 cm. long, of numerous 
pairs of spikelets, linear, flattened, the first glumes of the pedicellate spikelets conspicu- 
ous, imbricated; sessile spikelets 4-5 mm. long, deciduous with the rachis internode and 
pedicel; first glume linear, 2-keeled, silky between the keels, slightly longer than the 
second glume, 4.5-5.0 mm. long, awnless; second glume 4.0-5.0 mm. long, strongly 
compressed and keeled, the keel bowed out; sterile lemma ca. 3.5 mm. long, narrowly 
lanceolate, 2-keeled, conforming to the shape of the first glume, hyaline, the margin 
ciliate, lacking flower or palea; fertile floret ca. 3.0 mm. long, the keel of the lemma 
curved, conforming to the shape of the second glume, membranaceous, bifid at the apex 
and bearing a long awn, 3-4 cm. long; flower perfect; anthers 3, 1.5-1.8 mm. long, 
pinkish; palea 2.3-3.0 mm. long, hyaline. Pedicellate spikelet readily deciduous from the 
apex of the pedicel, its first glume oblong or obovate, stiff and flat, acuminate, somewhat 
asymmetric, bearing an awn ca. 10 mm. long, scabrous ciliate on the margins; second 
glume 3.5-5.0 mm. long, with a straight awn 2-10 mm. long; no flower present. Chromo- 
some number n = 10 from Costa Rican material. 

Scattered in northern Guanacaste; savannas, tuff outcrops, sea cliffs; 
Western Meseta Central; Boruca area and valley of Rio Grande de 
Terraba; elevations from sea level to 800 m. Late October to March. 
Mexico to Brazil; West Indies; Tropics of the Old World. 

DIGITARIA Haller 

REFERENCES: J. Th. Henrard, Monograph of the genus Digitaria, 
Univ. Pers. Leiden. 999 pp. 1950. J. F. Veldkamp, A revision of Di- 




FIG. 57. Diectomis fastigiata. A, rame; B, two views of a spikelet pair, showing 
enlarged sterile pedicellate spikelets. 



176 



BURGER: FLORA COSTARICENSIS 177 

gitaria Haller (Gramineae) in Malesia. Notes on Malesian Grasses VI, 
Blumea 21:1-80. 1973. 

Annual or perennial caespitose, rhizomatous, or stoloniferous grasses; leaf blades 
usually flat and lax; ligules membranaceous, sometimes ciliolate. Inflorescence of several 
to many unilateral racemes, these whorled or racemose along a central rachis; rachis of 
racemes triquetrous or flattened and winged, the spikelets appressed in 2 rows along the 
lower side of the rachis, in pairs or triads, rarely solitary or in groups of 4-5; pedicels of 
each group of unequal length. Spikelets ovate or lanceolate, dorsally compressed, 
planoconvex, disarticulating below the glumes, placed with the back of the fertile lemma 
toward the rachis; first glume a minute nerveless scale or absent; second glume from ca. 
one-fourth as long to as long as the spikelet, usually 3-5-nerved; lower floret represented 
by a sterile lemma possessing a minute palea which remains attached to the base of the 
fertile upper floret; sterile lemma usually about as long as the spikelet, flat on the back, 
5-9-nerved; fertile floret about as long as the spikelet, its lemma stiff but not rigid, ovate 
or lanceolate, convex, usually faintly 3-nerved and longitudinally striate, glabrous, 
grayish, tan, brown, or chocolate colored, its margins thin and flat, not inrolled, overlap- 
ping the margins of the palea and often meeting near the base; palea flat, of the same 
texture and appearance as the lemma and about as long; anthers 3; stigmas 2; caryopsis 
planoconvex, elliptical, whitish and opalescent. 

A large genus of about 170 species (Veldkamp, 1973) of grasses of 
tropical and warm temperate climates, abundant in both eastern and 
western hemispheres. Digitaria is related to Leptoloma, Reimaro- 
chloa, Hymenachne, and Leptocoryphium, and less closely to 
Panicum and Paspalum. Many of the species of Digitaria are abun- 
dant weeds of cultivated or waste areas, and a few are cultivated for 
forage, notably D. decumbens (pangola grass) in Central America. 
Species of Digitaria are usually easily recognizable by the very slender 
simple racemose inflorescence branches and narrow, more or less 
pointed spikelets. (Panicoideae: Paniceae.) 

KEY TO SPECIES OF Digitaria 

la. Mature fertile floret reddish brown to nearly black 2 

Ib. Mature fertile floret grayish or dull tan 6 

2a. Spikelets paired, densely covered with elongated silky or tan hairs which 
nearly conceal the spikelet and extend several mm. beyond the tip 

D. insularis 
2b. Spikelets paired or in triads, the white, golden, or purple hairs short, not 

extending more than 1 mm. beyond tip of spikelet 3 

3a. Spikelets paired; hairs of mature spikelet purple D. pittieri 

3b. Spikelets in triads or, rarely, 4-5 per group; hairs silvery or golden 4 

4a. Margins and tip of sterile lemma bearing stiff, glassy, golden bristles which, 

when young, extend beyond the tip of spikelet as a stiff brush D. argillacea 

4b. Margins of sterile lemma and second glume bearing fine appressed silky hairs; 

golden bristles not present 5 

5a. Hairs of second glume and sterile lemma with blunt, club-shaped tips, readily 
visible under 20 x magnification D. filiformis var. villosa 



178 FIELDIANA: BOTANY 

5b. Hairs of second glume and sterile lemma tapering to fine points, hair walls minutely 

roughened (visible under 400 x magnification) D. violascens 

6a. Spikelets 2 mm. or more long; first glume present or absent 7 

6b. Spikelets less than 1.5 mm. long; second glume and sterile lemma completely 

covering fertile floret; first glume absent D. longiflora 

7a. First glume absent; second glume less than half as long as spikelet . D. setigera 

7b. First glume present; second glume more than half as long as spikelet 8 

8a. Pedicellate spikelet when mature, bearing strongly spreading fine marginal 
cilia, often interspersed with thick bristles; subsessile spikelet similar or usu- 
ally with appressed pubescence only D. bicornis 

8b. Spikelets never possessing strongly spreading cilia; Spikelets of each pair 
always alike 9 

9a. Second glume and sterile lemma subequal, nearly or completely covering and con- 
cealing fertile floret 10 

9b. Second glume shorter and narrower than sterile lemma, exposing upper part and 

sides of fertile lemma 11 

lOa. Spikelets 3.5-4.0 mm. long; foliage heavily villous; inflorescence a whorl of 

closely ascending racemes D. costaricense 

lOb. Spikelets 1.9-2.1 mm. long; foliage more or less pubescent; inflorescence a 
panicle of solitary or paired spreading racemes along a slender rachis 

D. abyssinica 

lla. Rachis of racemes bearing scattered elongated pustulose-based hairs 13 

lib. Rachis of racemes not bearing elongated hairs 12 

12a. Back of sterile lemma visibly 5-nerved, internerves scarcely wider than 
nerves; coarse stoloniferous perennial, sometimes with rhizomes; leaf blades 

narrowly linear, scabrous; cultivated crop D. decumbens 

12b. Back of sterile lemma visibly 3-nerved, internerves broad, first pair of lateral 
nerves appearing marginal; plants with decumbent stems; leaf blades short 

and broad, papillose-pilose; wild plants D. ciliaris 

13a. Spikelets 1.8-2.0 mm. long; inflorescence of branched racemes; sterile lemma 5- 

nerved D. velutina 

13b. Spikelets 2.1-2.4 mm. long; inflorescence of simple, unbranched racemes; sterile 
lemma 7-nerved D. horizontalis 

Digitaria abyssinica (Hochst.) Stapf, Gr. Brit. Somal. Kew Bull. 
1907:213. Panicum abyssinicum Hochst., in A. Rich., Tent. Fl. 
Abyss. 2:360. 1851. Syntherisma abyssinica (Hochst.) Newbold, Tor- 
reya 24:8. 1924. Figure 58. 

Duration indefinite; culms long-decumbent and rooting at the nodes, the erect 
branches 20-40 cm. tall; plants branching freely from the base and from nodes of rooted 
stems; culms 1.0-1.5 mm. thick, hollow, glabrous, often purple; nodes prominent; 
prophylla 20-30 mm. long; sheaths shorter or longer than the internodes, papillose- 
pilose; ligules 1-2 mm. long, membranaceous, erose, brownish or purplish; blades rather 
short and broad, 4-9 cm. long, 3-11 mm. wide, papillose-pilose on both sides, rounded to a 
broad base. Peduncles slender, glabrous, exserted up to 15 cm., terminal on the main 
culm or on erect leafy branches; inflorescence an open panicle of racemes, 5-10 cm. long, 
wider than long, the rachis 2-6 cm. long, the racemes solitary or subopposite; rachis of 




FIG. 58. Digitaria abyssinica. A, two views of a spikelet; B, fertile floret; C, portion of 
a raceme; D, blooming plant. 

179 



180 FIELDIANA: BOTANY 

racemes slender, triquetrous, scabrous on the angles, less than 0.5 mm. thick; spikelets 
paired, unequally pedicellate, the shorter pedicel 0.8-1.1 mm. long, the longer one 
1.7-2.5 mm. long. Spikelets ovate, rather plump, barely acute, 1.9-2.1 mm. long, often 
with some purple coloration; first glume prominent, ovate-deltoid, 1-nerved, 0.3-0.7 mm. 
long; second glume ovate, blunt, ca. five-sixths as long as the spikelet, 1.6-1.8 mm. long, 
3-6-nerved; sterile lemma as long as the spikelet and slightly exceeding the fertile one, 
7-nerved, but the inner 3 nerves much more conspicuous, glabrous or with short silky 
pubescence on the upper margins; fertile lemma ovate, plump, minutely striate, usually 
grayish, 1.7-1.9 mm. long, the palea exposed at maturity; anthers 3, orange or purplish, 
1.0-1.1 mm. long; stigmas purple; caryopsis elliptical, whitish-opalescent, 1.3-1.4 mm. 
long. Chromosome number n = 18 from a Costa Rican specimen. 

Becoming common in disturbed areas, particularly in cafetals; 
Meseta Central, Orosi and Turrialba Valleys; probably blooming 
yearlong. Native to northeastern and Central Africa and there known 
as a weed in coffee plantations; not previously known from the western 
hemisphere, except as a cultivated introduction in the United States 
(Newbold, I.e.). 

Henrard distinguishes this species from D. vestita Fig. & De- 
Notaris, but Stapf, in Fl. Trop. Africa 461 (1919), included D. vestita 
as a synonym of D. abyssinica. Our specimens seem very uniform 
except for the slight ciliation of the second glume and sterile lemma of 
some specimens. 

Digitaria argillacea (Hitchc. & Chase) Fernald, Rhodora 22:104. 
1920. Syntherisma argillacea Hitchc. & Chase, Contr. U.S. Natl. 
Herb. 18:296. 1917. Figure 61. 

Duration indefinite; plants 28-60 cm. tall, the culms erect, in small tufts; culms slen- 
der, 1 mm. thick, hollow, glabrous; sheaths papillose-pilose, about as long as the inter- 
nodes; ligule a lacerate, ciliolate membrane, 0.7-1.2 mm. long; blades flat, 4-9 cm. long, 
2-5 mm. wide, papillose-pilose. Peduncle included or exserted, glabrous. Inflorescences 
solitary, terminal on leafy culms, 6-12 cm. long, of 2-6 erect or spreading racemes along a 
common rachis 1-3 cm. long; individual racemes 1-12 cm. long, the rachis slender, 0.2-0.3 
mm. wide, triquetrous, strongly scabrous and sometimes with scattered elongate hairs; 
spikelets in triads or pairs, the shortest pedicel 0.5-1.0 mm. long, the longest up to 2.5 
mm. long. Spikelets 1.7-1.8 mm. long, not including the bristles, ovate, acute; first glume 
absent; second glume triangular, 1.2-1.6 mm. long, 3-nerved; sterile lemma as long as 
the spikelet, 5-7-nerved; central internerve areas glabrous, the lateral ones pubescent 
with fine silky hairs which are mostly hidden by abundant thick, glassy golden bristles 
which, until full maturity, are appressed and overtop the spikelet bracts up to 1 mm.; 
similar bristles on the margins and tip of the second glume; bristles finally widely 
spreading at maturity of the fruit; tips of bristles slightly dilated and terminating in an 
abruptly acuminate point; fertile floret plump, ovate, 2.3:1, deep brown, striate; palea 
similar; caryopsis elliptic, whitish-opalescent, 1.3 mm. long. 

Open dry areas, savannas; rare; elevations from sea level to 1,200 
m.; Bagaces, Hacienda Argentina, Carillos de Poas, Puntarenas, 
Boruca, San Jose. August to December. 



BURGER: FLORA COSTARICENSIS 181 

This species was originally described from Puerto Rico and has been 
recorded from Cuba as well as Central America. The type from Puerto 
Rico has mostly basal foliage, but the spikelets are a good match for 
our specimens. Our specimens have leafy culms and are vegetatively a 
good match for D. hirsuta Swallen, Ann. Missouri Bot. Gard. 30:172. 
1943. The latter species, however, lacks the conspicuous glassy golden 
bristles found on the spikelets of D. argillacea. Spikelets of both 
species have peculiar bulbous-tipped hairs ending in a sharp mucro. 
Both of these entities need more field study to determine whether they 
are actually distinct. Digitaria hirsuta may be a form of D. argillacea 
lacking the glassy golden bristles. Similar occurrences are known in 
other species of the genus. 

Digitaria bicornis (Lam.) Roem. & Schult., Syst. 2:470. 1817. Pas- 
palum bicorne Lam., Tabl. Encycl. 1:176. 1791. Digitaria diversiftora 
Swallen, Rhodora 65:356. 1963. An extended synonomy for this species 
is given by Veldkamp in Blumea 21:30-31. 1973. Figure 59. 

Duration indefinite; culms long-decumbent and rooting at the nodes, the erect 
branches 10-85 cm. long, branching from the lower nodes; culms 1-2 mm. thick, hollow, 
glabrous; leaf sheaths longer or shorter than the internodes, bearing scattered elongate 
pustulose-based hairs, sometimes nearly glabrous; ligule a thin membrane, 1.5-3.2 mm. 
long; leaf blades 3-14 cm. long, 2-9 mm. wide, flat, nearly glabrous except for elongated 
pustulose-based bristles on the upper surface near the base. Peduncles glabrous, ex- 
serted up to 30 cm.; inflorescences terminal on the main culm or erect leafy branches, 
usually consisting of a single whorl of 3-6 racemes, rarely with a secondary whorl above 
these; racemes 5-14 cm. long, the rachis flattened, wing-margined, 0.7-1.0 mm. wide, the 
edges scabrous, the midrib winged; spikelets paired, unequally pedicellate, the shorter 
pedicel ca. 0.2 mm. long, the longer one up to 2 mm. long. Spikelets lanceolate, usually of 
2 kinds; length 2.9-3.3 mm.; first glume small to obsolete, deltoid or bifid, 0.2-0.4 mm. 
long; second glume 1.5-2.2 mm. long, 3-nerved, triangular 6:1, ciliate; sterile lemma as 
long as the spikelet, 5-nerved; lemma of fertile floret ovate, 6:1, acute, 3-nerved, grayish 
to stramineous, the palea equal to the lemma; anthers 3, purple, 0.5-0.6 mm. long; 
caryopsis tan to whitish, opalescent, elliptical-ovate, 1.8-1.9 mm. long; subsessile 
spikelet usually slightly marginally ciliate, the nerves of the sterile lemma equidistant; 
pedicellate spikelet strongly ciliate, the hairs divergent at maturity, arising between the 
lateral nerves of the sterile lemma and on its margins; silky pubescence interspersed 
with yellowish papillose-based bristles; inner nerves of sterile lemma distant from the 
midnerve, so that only 3 nerves are normally visible, the others obscured by the pubes- 
cence. Chromosome number n = 36 from a Costa Rican specimen. 

Beaches, sand bars, roadsides, disturbed open areas; sea level to 
1,600 m.; common in Guanacaste and on Pacific beaches; Limon; appar- 
ently less common in the interior. Probably blooming yearlong. Florida 
and southern Texas southward to Costa Rica; West Indies; Colombia 
and Venezuela. 








FIG. 59. Digitaria species. D. bicornis: A, two rachis internodes, showing glabrous 
subsessile spikelets paired with strongly ciliate pedicellate ones; B, a single spikelet; D. 
horizontalis: C, a spikelet pair, rachis bearing papillose-based hairs; D. ciliaris: D, two 
views of a spikelet. 



182 



BURGER: FLORA COSTARICENSIS 183 

Digitaria ciliaris (Retz.) Koel., Descr. Gram. 27. 1802. Panicum 
ciliare Retz., Obs. 4:16. 1786. Panicum sanguinale auct., non L. Di- 
gitaria adscendens (H.B.K.) Henr., Mon. Digitaria 9. 1950. Digitaria 
abortiva Reeder, J. Arnold Arbor. 29:291. 1948. An extended 
synonomy is provided by Veldkamp, I.e. Figure 59. 

Duration indefinite; plants mat-forming, the culms long-decumbent, rooting at the 
nodes; erect portions 30-60 cm. long; branching abundant from the decumbent portions 
of the culms; prophylla 2 cm. long, with extra marginal nerves; their margins silky 
pilose; culms ca. 2 mm. thick, hollow, thin-walled, glabrous; sheaths longer or shorter 
than the internodes, more or less papillose-pilose; ligules membranaceous, 2.0-3.5 mm. 
long; blades flat, 5-12 cm. long, 5-9 mm. wide, more or less papillose-pilose, especially 
toward the base. Peduncles exserted up to 27 cm., glabrous; inflorescence 7-15 cm. long, 
of 2-10 spreading racemes, each 7-14 cm. long, borne in 1 or 2 whorls, the common rachis 
up to 2 cm. long. Spikelets paired, unequally pedicellate, the shorter pedicel 0.5-1.0 mm. 
long, the longer 2.0-3.1 mm. long; rachis narrowly winged, scabrous on the angles; 
spikelets of each pair alike, 2.7-3.4 mm. long, narrowly ovate, 4:1; first glume deltoid, 
nerveless, 0.3-0.5 mm. long; second glume triangular 4:1, 1.7-2.0 mm. long, 3-nerved, 
the margins and tip silky; sterile lemma the length of the spikelet, 3-5-nerved, short- 
silky between the lateral nerves and on the margins; fertile lemma slightly shorter, 
2.5-3.0 mm. long, grayish, striate; anthers 3, brownish red, 1.2-1.3 mm. long; stigmas 
purple. Chromosome number n = 27. 

Roadsides and open areas, sea level to 1,500 m. elevation, Pacific 
and Caribbean slopes. April to August, possibly yearlong. Tropics of 
both hemispheres; in the New World extending from the southern 
United States to Argentina. 

Digitaria costaricensis Pohl, Fieldiana, Bot. 38:5. 1976. Figure 60. 

Probably perennial; plants with long decumbent rooting culm bases, up to 80 cm. long, 
sometimes becoming buried and appearing rhizomatous; culms branching abundantly 
from lower and middle nodes, 1-3 mm. thick, hollow, thick-walled, glabrous; prophylla 
up to 2 cm. long, papillose-pilose; sheaths mostly longer than the internodes, densely 
retrorsely papillose-pilose, the hairs silky, up to 3.5 mm. long; ligule a thin erose mem- 
brane, decurrent on the sheath margins, 1.5-2.5 mm. long; blades soft, flat, 8-15 cm. 
long, 3.5-7.0 mm. wide, softly velvety. Peduncle glabrous, exserted up to 15 cm.; 
inflorescences terminal on erect leafy branches, 7-14 cm. long, narrow and erect, the 4-7 
racemes borne on a short rachis up to 2-3 cm. long; several short racemes of 1-several 
spikelets borne at the base of the longer racemes. Spikelets paired, rather remote on the 
slender triquetrous rachis which is strongly scabrous on the angles; subsessile spikelet 
reaching about to the base of the spikelet next above it; spikelets of the pair equal, 
3.5-4.0 mm. long; shorter pedicel 0.5-0.7 mm. long, the longer one 2.0-3.0 mm.; spikelets 
acute, narrowly ovate 3.4-4.2:1; first glume a thin evanescent nerveless truncate cuff- 
like scale, ca. 0.3 mm. long; second glume and sterile lemma equal, slightly longer than 
the fertile floret; both with short silky white hairs on the margins and in the outer 
internerves, somewhat silky on the back above the base and with scattered silky hairs on 
the remainder of the back; second glume slightly narrower than the sterile lemma, but 
covering the fertile floret completely, 5-7-nerved; sterile lemma similar, 7-9-nerved, the 
nerves equidistant; fertile floret 3.0-3.2 mm. long, the lemma narrowly ovate, acute, 




FIG. 60. Digitaria costaricensis. A, blooming plant; B, portion of a raceme; C, fertile 
floret; D, two views of a spikelet. 



184 



BURGER: FLORA COSTARICENSIS 185 

striate, grayish, faintly 3-nerved, the palea equal; stamens 3, the anthers purple, 0.9-1.5 
mm. long; stigmas purple. Mature fruit not seen. 

This species occurs at middle elevations in the region east and south 
of Cartago. It is a member of the section Aequiglumae Henrard, 
Monog. Digitaria 641. 1950. This is a group of about 16 species native 
to the American tropics and subtropics, the members having paired 
spikelets with the first glume weak or absent. The second glume and 
sterile lemma are subequal and usually exceed the fertile floret. 
Among this group, Digitaria costaricensis seems most closely similar 
to D. aequiglumis (Hack, et Arech.) Parodi, from which it differs in 
the following characteristics: heavily pubescent foliage, wider leaf 
blades, longer racemes, presence of a cuff-like first glume on the 
spikelets, more numerous nerves of the second glume and sterile 
lemma, longer anthers. 

Digitaria decumbens Stent, Bothalia 3:150. 1930. 

Plants perennial; culms 60-100 cm. long, branching intravaginally from the lower and 
middle nodes, glabrous, thin-walled, hollow, 2-3 mm. thick; bases often long-decumbent 
and rooting; prophyllum firm, strongly keeled, up to 3 cm. long; upper internodes very 
elongated; sheaths mostly shorter than the internodes, glabrous or more or less 
papillose-pilose above the node and near the apex; ligule membranaceous, minutely 
erose-ciliate, 1.8-2.5 mm. long; blades flat, firm, narrow, acuminate, somewhat keeled 
near the base, 5-20 cm. long, 3-6 mm. wide, scabrid. Peduncle exserted 5-25 cm., gla- 
brous, felty-puberulent at the apex; inflorescences terminal on leafy branches, usually 
composed of a single whorl of 5-7 spreading racemes, these 12-16 cm. long; rachis of 
racemes triquetrous, 0.5 mm. wide, the green herbaceous margins narrower than the 
whitish midrib, conspicuously scabrous on all the angles; pedicels triquetrous, scabrous; 
spikelets paired, or rarely solitary by abortion, unequally pedicellate, the shorter pedicel 
ca. 0.5 mm. long, the longer one up to 2.2 mm. Spikelets of the pair 3.0-3.5 mm. long, 
alike; first glume a deltoid to narrowly triangular nerveless scale; second glume one-half 
to two-thirds as long as the spikelet, lanceolate, ciliate; sterile lemma as long as the 
spikelet, 3.0-3.5 mm. long, lanceolate, acute, with 5 evident nerves and 2 inconspicuous 
marginal ones; margins of the lemma and the second internerve from the midrib ap- 
pressed silky; fertile lemma chartaceous, grayish, very inconspicuously nerved, lanceol- 
ate, acuminate; palea equal, both striate; anthers 3, purple, 1.2-1.6 mm. long; pollen 
collapsed and empty; stigmas purple; lodicules 2, fleshy, truncate. Digitaria decumbens 
is a sterile triploid, its somatic chromosome number being 2n = 27 from Costa Rican 
specimens. 

This species is widely cultivated in Costa Rica as a forage grass at 
low and intermediate altitudes, up to 2,000 m. It is especially common 
in Guanacaste. Introduced from Africa; cultivated or straying from 
fields by vegetative spread. 

Since D. decumbens sets no seed, it is propagated by transplanting 
the stolons. The common name is Pangola. 



186 FIELDIANA: BOTANY 

Digitaria filiform is (L.) Koel., Descr. Gram. 26. 1802. var. villosa 
(Walt.) Fernald, Rhodora 36:19. 1934. Panicum filiforme L., Sp. PL 
57. 1753. Syntherisma villosa Walt., Fl. Carol. 77. 1788. Digitaria 
villosa (Walt.) Persoon, Syn. 1:85. 1805. Figure 61. 

Duration indefinite; plants caespitose, erect; culms slender, glabrous; nodes glabrous; 
sheaths shorter than the internodes, the lower ones papillose-hirsute, the upper gla- 
brous; ligule a conspicuously ciliolate membrane, 1.2-1.5 mm. long; blades narrow, 3-6 
mm. wide, elongate, the upper surface with scattered elongate pustulose-based hairs. 
Peduncle slender, glabrous, exserted; inflorescences solitary, terminal, 9-11 cm. long, of 
3-7 ascending racemes, each 6-8 cm. long; spikelets usually in triads, the pedicels of 
unequal length. Spikelets elliptical-ovate, acute, 2.0-2.2 mm. long; first glume absent; 
second glume ca. half as long as the spikelet, ovate, 3-nerved, ciliate with short hairs 
with club-shaped blunt tips, these conspicuous against the dark brown back of the 
mature fertile lemma; sterile lemma as long as the spikelet, 5-nerved, the central inter- 
nerve areas glabrous, the others with appressed hairs similar to those of the second 
glume; fertile floret ca. 2.0 mm. long, the lemma dark brown, striate, the wide thin 
margins nearly covering a palea of similar color and texture; anthers 3, purple, ca. 0.9 
mm. long. 

The above description is based largely on the specimen listed below. 
The determination is somewhat doubtful, since the only available 
specimen is inadequate. The club-shaped hairs of the spikelets place it 
in Henrard's group Clavipilae, along with such species as D . filiformis 
and D. leucocoma (Nash) Urban. Our specimen differs from typical Z). 
filiformis of temperate North America in its larger spikelets and from 
D. villosa in having glabrous medial internerves on the sterile lemma 
and in its shorter, denser racemes. Unless more adequate specimens 
are collected, we cannot be sure of its identity. San Jose, San Jose, 
1,100 m., Hitchcock 8498, 22-24 October 1911. 

Digitaria horizontalis Willd., Enum. PL 92. 1809. Figure 59. 

Duration indefinite; plants sprawling, the culms long-decumbent and rooting at the 
lower nodes, branching freely from the lower nodes; prophylla prominent, 1.5-3.5 cm. 
long; culms ca. 2 mm. thick, hollow, the internodes glabrous and shining; nodes rather 
prominent; foliage soft, sheaths longer than the internodes, papillose-pilose, less so 
toward the top of the plant; ligule a thin brownish membrane, 1.5-1.8 mm. long; blades 
flat, 3-14 cm. long, 3-9 mm. wide, velvety. Peduncle slender, exserted up to 25 cm., 
glabrous; inflorescences solitary and terminal on the main culm or on leafy branches; 
panicle up to 15 cm. long, very broad, the elongated slender racemes 4-12 cm. long, 
borne on a common rachis up to 4 cm. long, the lower ones whorled, the upper often 
paired or solitary; rachis of racemes triquetrous, ca. 0.5 mm. wide, the narrow herbace- 
ous margins narrower than the midrib, scabrous on the angles, bearing scattered elon- 
gated, slender, glassy, papillose-based hairs. Spikelets paired, unequally pedicellate, the 
shorter pedicel 0.3-0.5 mm. long, the longer one 1.3-2.0 mm. long; spikelets narrowly 
ovate, acute, 2.1-2.4 mm. long; first glume deltoid, 0.1-0.2 mm. long; second glume ca. 
half as long as the spikelet, 1.0-1.1 mm. long, narrowly triangular, 3-nerved, ciliate on 






J&t 



FIG. 61. Digitaria species. D. velutina: A, panicle and two views of a spikelet; D. 
filiformis, var. villosa: B, two views of a spikelet; D. argillacea: C, two views of a 
spikelet. 



187 



188 FIELDIANA: BOTANY 

margins and tip; sterile lemma as long as the spikelet, lanceolate, acute, 7-nerved, ciliate 
with short, silky hairs; fertile lemma stramineous or grayish, minutely striate, slightly 
shorter than the sterile lemma; caryopsis lanceolate, tan, ca. 1.8 mm. long. Chromosome 
number n = 18 from Central American material. 

Occasional on Caribbean and Pacific beaches, also at Tuis, Puerto 
Viejo and Siquirres. Blooming July to February, probably yearlong. 
Southern Florida; West Indies; tropical America from Guatemala to 
Brazil and Paraguay. 

The nomenclature of this species is much confused. Our material has 
been identified by Veldkamp. 

Digitaria insularis (L.) Mez ex Ekman, Beitr. Gramineenfl. Mis- 
iones. Ark. Bot. 11:17. 1912. Andropogon insulare L., Syst. Nat. ed. 
10:2:1304. 1759. Trickachne insularis (L.) Nees, Agrost. Bras. 86. 
1829. Figure 63. 

Vigorous perennial; plants 80-130 cm. tall, erect; bases of culms with swollen, woolly 
bracted innovations; culms branching from middle and lower nodes, up to 3 mm. thick, 
hollow, glabrous; nodes glabrous; sheaths mostly papillose-pilose, rarely glabrous; 
ligules 4-6 mm. long, thin, tan, membranaceous; blades lax, flat, 20-50 cm. long, 10-17 
mm. wide, scabrid. Peduncle glabrous, exserted 10-50 cm.; inflorescences terminal on 
the main culm or on leafy branches, narrow, cylindric, 20-35 cm. long, 2-10 cm. wide; 
racemes numerous, ascending, mostly 10-15 cm. long, the axis slender, trigonous, scab- 
rous on the angles; spikelets paired, equal, one pedicel 0.7-2.0 mm. long, the other 
2.5-5.0 mm. long, both slender, trigonous, scabrous. Spikelets narrowly ovate, caudate, 
4.2-4.6 mm. long, densely covered with abundant fawn-colored hairs up to 6 mm. long 
and extending beyond the summit of the spikelet as much as 5 mm.; first glume mem- 
branaceous, nerveless, triangular to ovate; second glume lanceolate, 3.5-4.5 mm. long, 
3-5-nerved, ciliate on the margins; sterile lemma as long as the spikelet (4.1-4.5 mm. 
long), narrowly ovate, acuminate, 7-nerved, the nerves obscured by the dense marginal 
hairs; fertile lemma narrowly ovate, acuminate, castaneous, minutely striate, 3.2-3.6 
mm. long; palea about equal; anthers 3, rarely exserted, 1.0-1.2 mm. long, tan. Chromo- 
some number n = 18 from Costa Rican specimens. 

Beaches, roadsides and forest margins, pastures; common in 
Guanacaste, also collected from Pigres, Atenas, Puente de Mulas, and 
Guacimo; elevations sea level to 1,200 m.; probably blooming yearlong. 
The plants are somewhat weedy. Florida and southern Texas to 
Arizona, southward to Argentina; West Indies. 

The fertile floret is elevated above the insertion of the second glume 
and sterile lemma on a thick rachilla internode 0.2-0.4 mm. long. This 
feature was formerly used as a generic character to separate 
Trichachne from Digitaria. 

Digitaria longiflora (Retz.) Pers., Syn. PI. 85. 1805. Paspalum 
longiftorum Retz., Obs. Bot. IV:15. 1786. Figure 62. 




FIG. 62. Digitaria longiflora. A, blooming plant; B, two views of a spikelet; C, verru- 
cose hair from a spikelet, greatly enlarged. 



189 



190 FIELDIANA: BOTANY 

Duration indefinite; plants forming large patches by means of long, abundant, freely 
branching stolons; flowering culms ascending to erect, 10-25 cm. tall, branching occa- 
sionally from the lower nodes; culms 1 mm. or less thick, hollow, glabrous; nodes dark, 
contracted; leaves 3-4 per culm, mostly clustered near the base; lower sheaths overlap- 
ping, the internodes short; peduncle very elongated, exserted, forming more than half 
the height of the plants; ligule a thin whitish membrane, 0.5-1.0 mm. long; leaf blades 
flat, 1.5-4.0 cm. long, 3-5 mm. wide, 5-8 x longer than wide, glabrous except for a few 
small cilia near the subcordate base. Inflorescence of 2 or rarely 3 conjugate slender 
racemes borne at the tip of the peduncle, widely spreading; racemes 4-5 cm. long; rachis 
flat, green, ca. 1 mm. wide, naked for 1-2 mm. at the base; spikelets crowded, borne in 
trios, these alternating along the sides of the narrow midrib. Spikelets of each trio alike, 
but borne on pedicels of unequal length, elliptic or slightly obovate 2:1, acute at the 
apex, 1.2-1.3 mm. long; first glume absent; second glume and sterile lemma equal, 
completely covering the fertile lemma or only its tip exposed; second glume 5-nerved, 
minutely pubescent between all of the nerves and on the margins; sterile lemma similar 
but 7-nerved, pubescent on the margins and outer internerves, the internerves adjacent 
to the midrib glabrous; fertile lemma grayish, ca. 1.2 mm. long, minutely striate, acute 
at the apex, enclosing a palea of equal length; anthers 3, purple, 0.7-0.8 mm. long; 
stigmas purple. 

Sandy beach of the Caribbean at Tortugero, Pohl & Lucas 13030. 
December. This is apparently the only collection from the mainland of 
North America. West Indies. Introduced from the Old World; native 
to Africa and Asia. 



Digitaria pittieri (Hack.) Henrard, Monog. Gen. Digitaria 570. 
1950. Panicum pittieri Hack., Oesterr. Bot. Z. 51:367. 1901. Valota 
pittieri (Hack.) Chase, Proc. Biol. Soc. Wash. 19:188. 1906. Trichachne 
pittieri (Hack.) Hitchc., Proc. Biol. Soc. Wash. 40:83. 1927. Figure 63. 

Duration indefinite; plants erect or scrambling, the culm bases decumbent and rooting; 
culms branching freely, ca. 1 mm. thick, hollow, glabrous; prophylla prominent, 2-4 cm. 
long, thin and soft, with 2 minor nerves marginal to each keel; sheaths loose, longer or 
shorter than the internodes, more or less papillose-hirsute; blades soft, rather short and 
broad, 6-10 cm. long, 7-11 mm. wide, flat, more or less papillose-pilose on both sides; 
ligule membranaceous, 1.0-2.5 mm. long. Peduncle slender, glabrous, exserted up to 25 
cm. Inflorescences numerous, terminal on leafy branches, 6-12 cm. long, of 5-10 slender 
ascending or rarely horizontally spreading racemes borne on a common rachis 1-4 cm. 
long; rachis and branches slender, triquetrous, bearing scattered, thin, elongate, 
pustulose-based hairs up to 4 mm. long; spikelets paired, rarely in triads near the base of 
the raceme, or solitary and accompanied by a minute abortive spikelet; pedicels slender, 
angular, the shorter one of the pair 0.2-0.3 mm. long, the longer one 1.5-3.0 mm. long. 
Spikelets dorsally compressed, lanceolate, 3.0-3.7 mm. long, marginally ciliate with soft 
erect purple hairs, these surpassing the tip of the spikelet up to 1 mm.; first glume 
obsolete or minute, up to 0.3 mm. long, truncate, deltoid, or bidentate, glabrous; second 
glume ca. three-fourths as long as the spikelet, narrowly triangular, 3-nerved, 2.0-2.7 
mm. long, marginally ciliate with erect hairs; sterile lemma as long as the spikelet, 
7-nerved, heavily marginally ciliate with shorter hairs in the internerves; fertile floret 
lanceolate, 2.8-3.0 mm. long, firm, castaneous, longitudinally striate, acuminate, the 






FIG. 63. Digitaria species. D. violascens: A, spikelet triad; B, spikelet; C, fertile 
floret; D. insularis: D, two views of a spikelet; E, fertile floret; D. pittieri: F, spikelet 
pair attached to the rachis. 



192 FIELDIANA: BOTANY 

margins thin; palea similar in color and texture, ca. as long as the lemma; caryopses 
produced; anthers 3, tan, 1 mm. long. 

Endemic to Costa Rica; rare, Meseta Central and Cartago Valley, 
1,000-1,400 m. elevation. Pastures, roadsides, thickets, river banks. 
September to February. 

This species is readily distinguished from others of the genus Di- 
gitaria by the dense purple marginal hairs of the spikelets. The type 
number, Pittier & Durand 6945, was collected by Tonduz as his 
number 749, from the banks of the Rio Tiliri near San Jose in 1892. The 
species was subsequently collected in 1911 at Alajuela and San Jose, at 
Dulce Nombre near Cartago in 1924, and at Ujaras in 1936. It has not 
been collected since, but may persist in the Meseta Central. The elon- 
gated shape of the spikelets and their hairiness suggest a relationship 
toD. insularis. The elongated trichomes of the inflorescence branches 
are similar to those of D. horizontalis. 

Digit aria setigera Roth ex Roem. & Schult., Syst. Veg. 2:474. 1817. 
var. setigera D. sanguinalis auct., non Scop. D. adscendens auct., non 
Henrard. An extensive synonymy is given by Veldkamp, I.e. 

Duration indefinite; plants forming mats or patches, the culms glabrous, hollow, 
1.5-2.5 mm. thick, long-decumbent and rooting at the lower nodes; erect portions of the 
culms up to 120 cm. long; branching free from lower nodes; prophylla up to 8 cm. long, 
with multiple lateral nerves; sheaths mostly shorter than the internodes, more or less 
papillose-pilose; ligule a tan membrane, 2.5-3.5 mm. long; blades flat, 4-28 cm. long, 4-12 
mm. wide, usually with a few papillose hairs near the base on the upper surface, some- 
times pilose all over, the surfaces usually scabrous. Peduncles long-exserted, up to 40 
cm. long, glabrous; inflorescences terminal on leafy branches, usually 10-15 cm. long, 
composed of 1 to several whorls of racemes borne on a common axis up to 6 cm. long; 
racemes 3-11, each 5-15 cm. long, spreading; rachis of racemes winged, 0.5-1.0 mm. 
wide, scabrous on the margins, the midrib keeled. Spikelets paired, unequally pedicel- 
late, the shorter pedicel of the pair 0.3-0.8 mm. long, the longer 1.7-2.7 mm. long; 
spikelets 2.4-3.5 mm. long, ovate 3:1 to 4:1; first glume absent or a minute cufflike scale 
0.1 mm. long; second glume 0.7-1.3 mm. long, less than half the length of the spikelet, 
rectangular or bilobed at the apex, 1-3-nerved, ciliate, the hairs overtopping the scale; 
sterile lemma the length of the spikelet, 5-7-nerved, the central pair of nerves remote 
from the midrib; lateral internerves and margins of the lemma silky-ciliate; fertile lemma 
slightly shorter than the sterile lemma, tan or grayish, striate, faintly 3-nerved, acumi- 
nate, its palea equal in length; anthers 3, reddish brown, 0.7-1.3 mm. long; stigmas 
purple; caryopsis elliptical, whitish-opalescent. Chromosome number n = 35, 36 from 
Costa Rican specimens. 

Occasional in open places and roadsides; Colonia Carmona, San Jose, 
Guapiles, Limon, Isla del Coco; sea level to 1,100 m. Caribbean coast of 
Honduras. Not previously recognized from Central America, but 



BURGER: FLORA COSTARICENSIS 193 

probably occurring elsewhere in the American tropics. Tropical Asia, 
Australia, Jamaica, Surinam. 

Digitaria velutina (Forsk.) Beauv., Ess. Nouv. Agrost. 51. 1812. 
Phalaris velutina Forsk., Fl. Aegypt. Arab. 17. 1775. NotZ). velutina 
(DC) Hitchc., Proc. Biol. Soc. Wash. 40:84. 1927. Figure 61. 

Duration indefinite; plants 30-60 cm. tall; bases of culms long-decumbent and rooting, 
forming circular patches; branching mostly from the rooted basal portions; prophylla 
2-keeled, 1.5-2.5 cm. long; culms 1.5-1.8 mm. thick, hollow, thin-walled, glabrous; nodes 
contracted, glabrous; leaves 1-4 per culm; sheaths shorter or longer than the internodes, 
papillose-pilose, keeled near the apex; ligule a tan membrane, 1.8-2.0 mm. long; leaf 
blades thin, flat, 6-10 cm. long, 6-10 mm. wide, appressed-pilose, somewhat keeled near 
the subcordate base. Peduncle slender, exserted 14-30 cm., glabrous, the interior filled 
with pith; inflorescences terminal on apical peduncles. Inflorescence panicled, 8-12 cm. 
long, 10-14 cm. wide, composed of 11-28 slender branches, the lowermost ones usually 
whorled, the upper ones paired or solitary; lower branches up to 10 cm. long, pinnately 
branched with spreading branches 2-3 cm. long, the upper branches simple; rachis 
triquetrous, narrowly winged, scabrous on the angles and bearing scattered long hairs; 
the spikelets paired, equal, one subsessile, the other on a pedicel up to 1.5 mm. long. 
Spikelets purplish, 1.8-2.0 mm. long; first glume minute, ca. 0.1 mm. long, or obsolete; 
second glume 1.5-1.7 mm. long, oblong to ovate, 3-nerved, the internerves villous; 
sterile lemma as long as the spikelet, 5-nerved, villous on the marginal internerves and 
edges; fertile lemma exposed near the tip, grayish, faintly nerved, ovate, acute, the 
margins covering the edges of a slightly shorter palea of similar texture; caryopsis 
elliptical, whitish-opalescent, 1.2-1.3 mm. long. Chromosome number n = 9. 

Our only specimen is the following: San Jose, Ciudad Universitaria, 
disturbed subsoil in area of new library building. Pohl & Davidse 
11075, 11 September 1968. Arabia to tropical Africa. Apparently pre- 
viously unreported from the western hemisphere. 

Digitaria violascens Link, Hort. Berol. 1:229. 1827. Panicum vio- 
lascens (Link) Kunth, Rev. Gram. 1:33. 1829. An extended synonomy 
is given by Veldkamp, Rev. Digitaria Malesia 63 (1972). Figure 63. 

Duration indefinite; plants erect, in small tufts; culms mostly unbranched, slender, ca. 
1 mm. thick, hollow, thin-walled, glabrous; nodes glabrous, not prominent; foliage 
mostly basal, the uppermost leaf blade reduced; sheaths shorter than the internodes, 
glabrous; ligule an erose membrane 1.0-2.3 mm. long; blades few per culm, 4-17 cm. long, 
3-5 mm. wide, glabrous, sometimes scaberulous on the upper surface or with a few 
elongated papillose-based hairs on the upper surface near the base. Peduncle slender, 
exserted up to 13 cm.; inflorescences solitary and terminal on leafy culms, 3-10 cm. long, 
consisting of 2-7 slender, arching racemes borne in 1-2 whorls, the common rachis up to 3 
cm. long; rachis of racemes flattened, 0.5-0.7 mm. wide, with a herbaceous border, the 
edges scabrous. Spikelets usually borne in triads, occasionally 4 or 5 together and rarely 
solitary by abortion of spikelets; pedicels of varying length, the shortest of the triad 



194 FIELDIANA: BOTANY 

0.2-0.3 mm. long, the middle one 0.8-1.0 mm., the longest 1.3-2.0 mm. long, scabrous, 
the apex dilated into a disk. Spikelets of each group equal, ovate 2:1, 1.4-1.5 mm. long, 
first glume absent, the second glume and sterile lemma thin, white; second glume 1.3-1.4 
mm. long, slightly shorter and narrower than the spikelet, usually 3-nerved, rarely 
5-nerved, the nerves anastomosing near the tip; sterile lemma as long as the spikelet, 
usually 5-nerved, rarely 7-nerved; internerves of the sterile lemma and second glume 
bearing appressed white silky hairs, their walls verrucose-roughened under 400 x 
magnification; fertile floret about as long as the spikelet, deep chestnut brown at matur- 
ity; lemma minutely striate, faintly 3-nerved; palea similar; caryopsis elliptical, 1.0-1.1 
mm. long, white, opalescent; anthers 3, reddish, 0.4-0.6 mm. long. Chromosome number 
n = 18 from Costa Rican specimens. 

Open roadsides and waste ground, sea level to 1,500 m. elevation; 
San Jose area, General Valley, San Vito, Golfito. Blooming yearlong. 
Tropics of Asia and Australia; introduced in the western hemisphere. 

This species may be confused with D. panicea (Sw.) Urban, which 
differs by having a narrow triquetrous rachis, spikelets bearing capi- 
tate hairs, and ciliolate ligules. 

ECHINOCHLOA Beauvois 

REFERENCES: F. W. Gould, M. A. Ali, & D. E. Fairbrothers, A 
revision of Echinochloa in the United States, Amer. Midi. Naturalist 
87:36-59. 1972. A. S. Hitchcock, The North American species of 
Echinochloa, Contr. U.S. Natl. Herb. 22:133-153. 1920. K. M. 
Wiegand, The genus Echinochloa in North America, Rhodora 
23:49-65. 1921. 

Annual or perennial, caespitose, decumbent, or rhizomatous grasses; culms usually 
solid, the lumen filled with aerenchyma; ligule absent or consisting of a dense row of stiff 
hairs. Inflorescence a terminal panicle, the branches mostly simple, bearing paired or 
clustered subsessile spikelets. Disarticulation below the glumes, the spikelets elliptical 
or ovate, dorsally compressed, plano-convex; first glume one- to three-fourths as long as 
the spikelet, ovate, apiculate, 3-5-nerved; second glume and lower lemma subequal, as 
long as the spikelet, apiculate or the lemma bearing a terminal awn; second glume 
5-7-nerved, convex, usually hispid on the nerves; lower lemma similar but usually 5- 
nerved and often tapering into a stiff, antrorsely scabrous awn; lemma containing a 
well-developed flat, membranaceous palea and in some species a staminate flower; sec- 
ond floret with a shiny, coriaceous, stramineous, longitudinally striate, ovate or elliptical 
lemma, its flat margins covering the edges of a flat palea of similar texture, except near 
the emergent tip; tip of lemma apiculate or beaklike; lodicules 2, truncate; stamens 3, the 
anthers yellow or orange; stigmas 2, plumose, purple. 

The species of Echinochloa frequent rich, moist, disturbed soil or 
occur in shallow water. The apiculate or awned spikelets, solid culms, 
and the usual absence of a ligule are marks of recognition. The genus is 



BURGER: FLORA COSTARICENSIS 195 

similar to Panicum in many respects, differing in the awned or apicu- 
late spikelets and the flat, not inrolled, margins of the fertile lemma. 
Echinochloa is similar to Hymenachne in its solid, aerenchymatous 
culms and hygrophilous habit. (Panicoideae: Paniceae.) 

KEY TO SPECIES OF Echinochloa 

la. Ligule a dense row of stiff bristles; lower floret staminate 2 

Ib. Ligule absent; lower floret neuter 3 

2a. Plants with short scaly rhizomes; spikelets awnless, 2.9-3.5 mm. long; fertile 

floret 2.5-2.7 mm. long; anthers 1.0-1.5 mm. long E. pyramidalis 

2b. Plants not rhizomatous, culms often decumbent and rooting; spikelets 4.5-6.0 
mm. long, sometimes with awn up to 18 mm. long; fertile floret 2.5-5.0 mm. 

long; anthers 1.5-3.6 mm. long E. polystachya 

3a. Spikelets awnless, borne in 4 rows on short racemes 1-2 cm. long; fertile floret 

1.9-2.2 mm. long E. colonum 

3b. Spikelets awn-tipped or awned, irregularly crowded along 4-6 cm. long racemes; 
fertile floret 2.5-2.8 mm. long E. crus-pavonis 

Echinochloa colonum (L.) Link, Hort. Berol. 2:209. 1833. 
Panicum colonum L., Syst. Nat. ed. 10. 2:870. 1759. An extended 
synonomy is given by Gould et al. Figure 64. 

Plants annual, erect and caespitose, or spreading and rooting from the lower nodes; 
culms usually 20-60 cm. tall, 2-3 mm. thick, hollow or filled with aerenchyma, branching 
near the base; lower nodes appressed-hispid, the upper glabrous; prophylla prominent, 
up to 8 cm. long; sheaths glabrous, shorter than the internodes, somewhat keeled; ligule 
absent; blades flat, 8-22 cm. long, 3-8 mm. wide, glabrous or with a few papillose-based 
marginal setae near the base. Peduncle exserted up to 10 cm.; inflorescence slender, 2-12 
cm. long, composed of 5-10 short, spikelike erect or ascending racemes, racemosely 
arranged along the slender, angular, scabrous rachis; individual racemes 0.7-2.0 cm. 
long, the rachis flattened; spikelets paired, minutely pedicellate, in 4 rows along the 
lower side of the rachis, which is papillose-hispid at its base and more or less along its 
length. Spikelets ovate, acute, not awned or barely apiculate, flattened on the first 
glume side, strongly turgid on the second glume side, often purple-blotched, 2.3-2.9 mm. 
long, the visible bracts appressed-hispid along the nerves; first glume 1.0-1.5 mm. long, 
3-nerved, broadly ovate, acute; second glume very convex, ovate, apiculate, 5-nerved, 
as long as the spikelet; sterile lemma flat, 5-nerved, as long as the spikelet, concealing an 
elliptical flat palea nearly as long; fertile lemma 1.9-2.2 mm. long, indurate, smooth and 
shining, faintly longitudinally striate and 5-nerved, elliptical 3:2, terminating in a minute 
greenish withering tip; palea flat, its margins overlapped by the flat edges of the lemma 
except at the tip; anthers 3, yellow, 0.7-0.8 mm. long. Chromosome number n = 27 from 
Costa Rican plants. 

Roadsides, pastures, beaches, banana groves, sea level to 1,100 m., 
but most common at low elevations near the coasts. June to December. 
Widespread in warm climates of the world, apparently introduced 
from the Old World. Certain plants may have leaf blades with trans- 
verse purple markings. 





B 




FIG. 64. Echinochloa colonum. A, inflorescence; B, two views of a spikelet; C, two 
views of the fertile floret. 



196 



BURGER: FLORA COSTARICENSIS 197 

Echinochloa crus-pavonis (H.B.K.) Schult., Mant. PL 2:269. 1824. 
Oplismenus crus-pavonis H.B.K., Nov. Gen. & Sp. 1:108. 1816. An 
extended synonomy is given by Gould et al. Figure 65. 

Duration indefinite, probably annual; plants 80-150 cm. tall, the culms erect or the 
bases decumbent and rooting from the lower nodes, branching from the lower nodes, 
thick and spongy, often 1 cm. or more thick, glabrous; nodes swollen, glabrous; lumen of 
internodes filled with aerenchyma which contains vascular bundles; prophylla promi- 
nent, up to 12 cm. long; sheaths shorter than the internodes, loose, glabrous, often 
purplish; ligule absent, a rounded ridge taking its place; blades flat, glabrous, usually 
12-60 cm. long, 7-25 mm. wide, scabrous-margined. Inflorescences terminal on the main 
culm or on erect leafy intravaginal branches, 10-30 cm. long, oblong to narrowly pyrami- 
dal, the branches, except the lowermost, mostly overlapping, 4-6 cm. long. Spikelets 
mostly paired, densely and irregularly clustered along the primary or secondary 
branches, obscuring the axes; rachis and branches angular, scabrous, often bearing 
pustulose-based stiff glassy hairs. Spikelets 2.8-3.5 mm. long, often purple, awn-tipped 
or awned, ovate; first glume 1.4-1.7 mm. long, broadly ovate or orbicular, abruptly 
acuminate, the margins enwrapping the base of the second glume, 3- or rarely 4-nerved; 
second glume as long as the spikelet, 5-nerved, ovate, cuspidate, bulging, bearing more 
or less appressed stiff hairs on the nerves and minutely hispid between them; sterile 
lemma as long as the spikelet, ovate, 5-nerved, similar to the second glume, enclosing a 
flat membranaceous elliptical palea two-thirds to three-fourths as long, awn-tipped or 
bearing a stiff scabrous awn up to 11 mm. long; fertile lemma 2.5-2.8 mm. long, ovate, 
caudate, shiny, faintly-nerved, tapering into a herbaceous withering tip; palea equal to 
the lemma and similar in texture; anthers 3, dark, 1.0-1.2 mm. long; lodicules small, 
truncate. Chromosome number of E. crus-pavonis is n = 18 from a number of Costa 
Rican specimens. 

Wet open areas and marshes, roadsides; sea level to 1,700 m. eleva- 
tion. Cartago area, San Jose, Nuestro Amo, Guanacaste. June to Oc- 
tober. Probably common, but little collected. Southern United States 
to Argentina; tropical Africa; Australia. 

This species exhibits a great deal of variation in awn length. Awn- 
less specimens appear very different from long-awned types, but fun- 
damental spikelet structure is the same. This species has been con- 
fused with E. crusgalli (L.) Beauv., but differs from the latter in the 
lack of minute bristles at the apex of the shiny part of the fertile 
lemma, as well as in chromosome number. Var. macera (Wiegand) 
Gould is said to have vestigial or absent palea within the sterile lemma. 
All of the Costa Rican specimens have a well-developed palea and 
belong to var. crus-pavonis. 

Echinochloa poly st achy a (H.B.K.) Hitchc., Contr. U.S. Natl. 
Herb. 22:135. 1920. Oplismenus polystachyus H.B.K., Nov. Gen. & 
Sp. 1:107. 1816. Figure 65. 

Duration indefinite, probably perennial; culms 1-3 m. or more long, decumbent and 
rooting abundantly at the lower nodes, sometimes forming large floating patches, gla- 




FIG. 65. Echinochloa species. E. cms-pavonis: A, base of leaf blade, lacking a ligule; 
B, base of culm; C, inflorescence; D, two views of a spikelet; E. polystachya: E, base of 
leaf blade, showing ligule; F, two views of a spikelet. 



198 



BURGER: FLORA COSTARICENSIS 199 

brous, spongy, up to 1.5 cm. thick, the lumen filled with aerenchyma containing vascular 
bundles; nodes glabrous or strongly appressed-hispid, swollen; branching intravaginal 
from the middle nodes; prophylla prominent, up to 13 cm. long, hispid-margined and 
with a conspicuous tuft of hispid hairs at the tip; sheaths shorter or longer than the 
internodes, glabrous or appressed papillose-hispid; ligule a dense V-shaped line of stiff 
tan hairs, 2-4 mm. long, continued onto the upper sheath margins as a few papillose- 
hispid hairs; leaf blades soft, flat, up to 50 cm. long and 3.5 cm. wide, with a prominent 
white midrib, glabrous, the margins scabrous, surfaces scabrous toward the tip. 
Inflorescences terminal; peduncle ridged, glabrous, up to 15 cm. long; panicle 20-35 cm. 
long, narrowly cylindrical, 2-5 cm. wide, the numerous ascending branches 2-11 cm. 
long, rachis angular, scabrous, with tufts of stiff, glassy, papillose-based hairs at the 
bases of the branches, along the rachises of the branches, and on the pedicels; spikelets 
subsessile or on pedicels up to 1 mm. long, their apices dilated into disks. Spikelets 
paired, in trios, or irregularly grouped on the lower sides of the primary branches, 
4.5-6.0 mm. long, elliptic or narrowly ovate, apiculate or awned, short-hispid on the 
nerves, greenish; first glume 1.9-4.2 mm. long, 5-7-nerved, broadly deltoid-ovate, clasp- 
ing the base of the second glume, its margins minutely ciliate; second glume and lower 
lemma about equal, as long as the spikelet; second glume convex, 5- or usually 7-nerved, 
apiculate or with an awn up to 7.5 mm. long; lower lemma usually 5-nerved, flat, apicu- 
late or with an antrorsely scabrous awn up to 18 mm. long, the palea elliptical, scabrous 
on the nerves, ca. as long as the lemma, enclosing 3 stamens with orange anthers 1.5-3.6 
mm. long (usually longer than those of the upper floret); upper floret 2.5-5.0 mm. long, 
the coriaceous elliptical lemma tapering into a laterally flattened greenish herbaceous 
beak up to 1 mm. long; palea similar to the lemma and about as long; lodicules 2, 
truncate; anthers 3; stigma purple, laterally exserted. Chromosome number n = 54 from 
Costa Rican specimens. 

Marshes near the coasts, often in standing water; Limon area, 
Cahuita, Tarcoles. June to September. Southern coast of the United 
States, through Mexico and Central America to Argentina; Caribbean 
Islands. 

This is the largest of the Central American species of Echinochloa 
and the most hygrophilous. Large stands are seen in marshes and 
possibly are grazed by livestock. The form with pubescent nodes and 
sheaths has been distinguished as var. spectabilis (Nees) Martinez, 
Rev. Arg. Agron. 9:318. 1942, based upon Echinochloa spectabilis 
(Nees) Link. None of our Costa Rican specimens is pubescent. 

Echinochloa pyramidalis (Lam.) H. & C., Contr. U.S. Natl. Herb. 
18:345. 1917. Panicum pyramidale Lam., Tabl. Encycl. 1:171. 1791. 
Echinochloa guadeloupensis (Hack.) Wiegand, Rhodora 23:63. 1921. 
Panicum spectabile, var. guadeloupense Hack., Notizbl. Bot. Gart. 
Berl. 1:328. 1897. Figure 66. 

Perennial, with short scaly creeping rhizomes; culms erect or sometimes decumbent 
and floating in water, up to 2 m. long; usually unbranched except for decumbent por- 
tions, lower nodes sometimes producing prop roots, glabrous, up to 1 cm. thick, solid, 




FIG. 66. Echinochloa pyramidalis. A, panicle; B, base of culm with rhizome; C, two 
views of a spikelet; D, two views of a fertile floret. 



200 



BURGER: FLORA COSTARICENSIS 201 

the lumen filled with aerenchyma containing vascular bundles; nodes glabrous, swollen; 
sheaths mostly shorter than the internodes, glabrous or papillose-hispid on the back; 
papillose-hispid on the upper margins below the ligule, somewhat keeled above; ligule a 
dense row of stiff tan hairs, 1-4 mm. long, those of the lower leaves longer, continued 
onto the upper sheath margins as a row of papillose-based hairs; leaf blades flat or 
somewhat keeled and folded near the base, glabrous, with a broad whitish midrib; 
margins scabrous, length 15-70 cm., width 5-13 mm., apex caudate-acuminate, base 
rather narrow. Peduncle smooth, cylindrical, exserted up to 30 cm.; inflorescence an 
open cylindrical panicle, tapering to a narrow apex, 13-45 cm. long, 2-10 cm. wide, with 
numerous simple lax ascending subverticillate branches up to 10 cm. long, the lower 
much longer than the upper; rachis angular, scabrous, exposed between the lower 
branches, bearing tufts of stiff pustulose-based glassy hairs around and below the bases 
of the branches and scattered single hairs along the primary branches; spikelets subses- 
sile in small clusters on short secondary branches, mostly below the primary branch. 
Spikelets elliptical 2:1, 2.9-3.5 mm. long, turgid, apiculate, greenish, often with purple 
blotches; first glume deltoid, apiculate, 1.5-2.2 mm. long, 5-nerved; second glume and 
lower lemma appressed-hispid on the nerves above the middle, as long as the spikelet; 
second glume 5-nerved, the nerves equidistant; lower lemma 5-nerved, the lateral 
nerves in pairs near the margins; lemma containing a palea nearly as long, elliptical, 
often purple; stamens 3, the anthers yellow, 1.0-1.5 mm. long; fertile floret 2.5-2.7 mm. 
long; lemma shining, stramineous, faintly 5-nerved; tip greenish, acute; upper margins 
minutely ciliolate; palea flat, equal to the lemma; anthers 3, shorter than those of the 
lower floret; lodicules small, truncate. Chromosome number n = 18 from a Nicaraguan 
specimen. 

This African species is known from Costa Rica only by the following 
specimen: Guanacaste, Finca La Taboga, 16 January 1969, P. & D. 
11661. It also occurs around the Lago de Nicaragua and on the Carib- 
bean Island of Guadeloupe. July and January. 



ECHINOLAENA Desvaux 

Much-branched decumbent annual; inflorescence a solitary reflexed unilateral spike 
borne at the tip of a bracted peduncle; spikelets pectinately arranged in 2 rows on the 
lower side of a flattened rachis, one spikelet terminating the rachis; first glume coriace- 
ous, convex below but flattened toward the tip, many-nerved, much longer than the 
remainder of the spikelet; second glume boat-shaped, acuminate, ca. two-thirds as long 
as the first; lower lemma nearly as long as the second glume, herbaceous, 5-nerved, with 
a prominent membranaceous palea and a staminate flower; upper lemma shorter than 
the lower one, smooth and shining, coriaceous, cucullate at the apex, the margins thin 
and exposed near the base, inrolled near the tip; basal callus prominent, truncate, rather 
fleshy. 

Echinolaena is a small genus of a few tropical American and African 
species. (Panicoideae: Paniceae.) 

Echinolaena gracilis Swallen, J. Wash. Acad. Sci. 23:457. 1933. 
Figure 67. 




FIG. 67. Echinolaena gracilis. A, blooming plant; B, two views of a spikelet; C, two 
views of a fertile floret. 



202 



BURGER: FLORA COSTARICENSIS 203 

Plants trailing, only the tips of the branches ascending; culms rooting at the nodes, 
hollow, appressed-pilose, often purplish, up to 50 cm. long; prophylla ca. 10 mm. long; 
nodes bearded; leaf sheaths 1.5-2 cm. long, much shorter than the internodes; strongly 
papillose-hispid; culms hollow, appressed-pilose, often purplish; ligule an arc of stiff 
hairs, ca. 0.5 mm. long; blades rather firm, 2-4 cm. long, 5-6 mm. wide, cordate at the 
base, with conspicuous whitish marginal bands, papillose-hispid on the margins and 
upper surface at the base, with a few scattered short hispid hairs on the upper surface, 
glabrous beneath; peduncle short or included in the sheath; spike 1, reflexed, 2-2.5 cm. 
long, a short stiff bract at the apex of the peduncle; spikelets 7-10.5 mm. long; first glume 
stiff, coriaceous, linear- triangular, acuminate, prominently ribbed on the outer surface, 
the upper third somewhat deflected to one side; outer surface prominently pustulose- 
hispid with spreading hairs; second glume herbaceous, broadly ovate, convex acuminate, 
9-nerved, papillose-hispid near the tip, 6-6.5 mm. long; lower lemma herbaceous, ovate, 
acute, 5-nerved, slightly hispid near the tip, the palea nearly as long as the lemma; 
flower staminate; second floret shorter than the first, the lemma glabrous, smooth and 
shining, coriaceous, 3.6-3.7 mm. long, elliptical, faintly 5-nerved, the margins covering 
the edges of the palea, thin and membranaceous near the base, somewhat inrolled above. 
Chromosome number n = 10 from a Venezuelan specimen. 

Known in Costa Rica only by the following specimen: Guanacaste, 
open Curatella-Byrsonima savanna, road to Las Animas, 2 km. E of 
Carretera Interamericana, elevation 200 m. , 4 December 1968, Pohl & 
Davidse 11527. Guatemala and Belize, northwestern Costa Rica; Co- 
lombia, Venezuela. Apparently rare. 



ELEUSINE Gaertner 

Caespitose or somewhat stoloniferous grasses; inflorescence of solitary or usually 
whorled one-sided spikes; spikelets sessile, densely imbricated in 2 rows along the lower 
side of a flattened rachis, laterally compressed and keeled, disarticulating above the 
glumes and between the florets; first glume 1-nerved, the second 5-nerved, both shorter 
than the lowermost floret; florets several; lemmas awnless, 3-nerved, the lateral nerves 
close to the midnerve; seed loose in the thin pericarp, strongly ridged. 

Eleusine is a small genus of less than 10 species, native to warmer 
parts of Africa and Asia. Our species is widespread as a weed in warm 
climates of the entire world. The genus is most closely related to 
Dactyloctenium. Although both genera have unilateral spikes, their 
spikelets are more similar to those of other genera of the Eragrosteae 
than to the Chlorideae. (Chloridoideae: Eragrosteae.) 

Eleusine indica (L.) Gaertn., Fruct. & Sem. 1:8. 1788. Cynosurus 
indicus L., Sp. PI. 72. 1753. Figure 68. 

Annual; culms 15-70 cm. long, erect or spreading, branching from the base, rarely 
from culm nodes; lower nodes often rooting; culms glabrous, hollow, thick-walled; stems 
leafy, the sheaths mostly overlapping, somewhat keeled, glabrous except for long soft 
hairs on their upper margins and the throat; ligules 0.5-1.0 mm. long, membranaceous, 
lacerate; leaf blades 5-30 cm. long, 2-5 mm. wide, mostly folded, glabrous beneath, with 




FIG. 68. Eleusine indica. Blooming plant, spikelet, floret, seed. 



204 



BURGER: FLORA COSTARICENSIS 205 

scattered long weak hairs above; peduncle glabrous, solid, pithy, exserted 6-20 cm., with 
a tuft of conspicuous hairs at the tip; inflorescence of 2-6 spikes, either all in one whorl, or 
with a solitary spike borne 1-2 cm. below; spikes 1.5-9 cm. long, the rachis flattened, 
0.7-1 mm. wide; spikelets 4-5 mm. long; first glume 1.5-2.2 mm. long, 1-nerved, lanceo- 
late as folded; second glume obscurely 5-nerved, 2.2-2.8 mm. long, narrowly ovate as 
folded, acute; florets 4-7; lemmas 2-3 mm. long, narrowly ovate as folded, glabrous; 
nerves 3, the lateral ones close to the keel, rarely an extra pair near the margins; keels 
scabrid; palea slightly shorter than the lemma, the keels salient, scabrid, converging to a 
boat-shaped tip; anthers 3, 0.2-0.5 mm. long, purplish. Chromosome numbers n = 9, 18. 

Common; open, disturbed sites; sea level to 1,500 m. elevation. 
Blooming is most common during the rainy season, but probably oc- 
curs to some extent yearlong. Introduced from the Old World; wide- 
spread in the Americas from the northern United States to southern 
South America. 

This is a very common weedy grass. Where it is trodden, it tends to 
form flat circular patches. Local name: Pata de gallina. Although most 
specimens have the nerves of the lemma very close to the keel, two 
collections from Costa Rica have an extra pair of nerves near the 
margins. 

ELYTROSTACHYS McClure 

Tall, hollow-stemmed bamboos; rhizomes pachymorphous; clumps of numerous elon- 
gated culms, becoming dependent on trees; internodes cylindrical, thin-walled; initial 
lateral bud 1 per node, but the primary branch soon rebranching from the base and 
producing a tuft of numerous slender leafy branches, usually with one larger than the 
rest; primary culm sheaths with narrow, attenuate, very strongly reflexed blades; 
auricular bristles elongate, flattened, very conspicuous on new shoots; foliage blades not 
visibly tessellate. Inflorescences borne on leafy or leafless stems, composed of pseudo- 
spikelets. These are bracted structures having several orders of branches, each sub- 
tended by a broad, short prophyll. The ultimate branchlets, concealed by the outer leafy 
bracts, are "spikelets" composed of a pair of glumelike bracts with a stiff, flattened rachis 
(pedicel) produced between them and supporting 1 or 2 perfect florets, the rachilla 
usually terminating in a rudiment; lemma awnless, grasping the palea only at its base; 
lodicules 3, flat; stamens 6; stigmas 2. (Bambusoideae.) 

Elytrostachys, a newly recognized genus, has only two species, one 
known only from Venezuela. Vegetatively, the plants can be separated 
from those of the larger species of Rhipidocladum by the strongly 
reflexed blades of the culm sheaths. 

Elytrostachys clavigera McClure, J. Wash. Acad. Sci. 32:176. 1942. 
Figure 69. 

Caespitose bamboo, forming large, open clumps of 30-50 culms, their bases decumbent 
and trailing, the upper parts clambering and looping up into trees; culms hollow, thin- 
walled, cylindrical, green, 4-8 cm. thick, glabrous; culm sheaths up to 25 cm. long, more 




FIG. 69. Elytrostachys clavigera. A, pseudospikelet; B, culm sheath showing narrow, 
strongly reflexed blade and elongated auricular bristles; C, young vegetative culm with 
reflexed culm blades and prominent auricular bristles; D, branch with foliage blades. 



206 



BURGER: FLORA COSTARICENSIS 207 

or less appressed-hispid with glassy white hairs; external ligule a stiff membrane, ca. 1 
mm. long, minutely ciliolate; internal ligule similar; auricular bristles numerous, erect, 
flattened, dark-colored, 3-5 cm. long; blades much narrower than the sheath apex, 
strongly reflexed, 4-7 cm. long, less than 1 cm. wide, hispid. Foliage-bearing branches 
arising from middle and upper nodes, each node bearing a dense fascicle of 10 or more 
slender branch lets, one (the primary branch) usually larger than the others; branchlets 
up to 50 cm. long, bearing reduced and early deciduous blades at their basal nodes and 
several larger blades, 6-18 cm. long and 13-32 mm. wide on their outer portions; blades 
flat, dark green, 6-18 cm. long, 13-32 mm. wide, ovate 6-7:1, tapering rather abruptly to 
a caudate apex, glabrous above, more or less hispid beneath; pseudopetiole up to 3 mm. 
long, puberulent above. Inflorescences numerous, forming false whorls at the nodes of 
leafy or leafless lateral branches; each inflorescence composed of a pseudospikelet 
covered with overlapping bracts; ultimate branchlet with a pair of sterile glumelike 
bracts at its base, a stiff, elongated, flattened puberulent pedicel extended above them, 
about as long as the bracts and supporting at its apex 1 or 2 florets; glumes none; lemma 
awnless, up to 17 mm. long; palea as long as the lemma or longer, grooved on the back 
and clasping a rachilla that is sterile or bears a second floret or a rudiment; flower 
perfect; lodicules 3, flat, unequal, vasculated; stamens 6, the anthers up to 8 mm. long; 
stigmas 2; disarticulation below the floret, the old pedicels with cuplike apices protrud- 
ing from the pseudospikelets. 

Forests at low elevations; La Selva, Buenos Aires, Tsaki. The last 
two specimens, collected in 1891 and 1895, respectively, were in fruit. 
Our recent collections from La Selva and Buenos Aires were vegeta- 
tive. The plants may be recognized vegetatively by their large, weak, 
cylindrical culms, strongly reflexed reduced blades of the culm 
sheaths, and the conspicuous elongated erect auricular bristles. Ven- 
ezuela to Honduras. 



ERAGROSTIS Wolf 

REFERENCES: L. H. Harvey, Eragrostis in North and Middle 
America, Unpubl. Ph.D. Diss. Univ. of Michigan. University 
Microfilms, Ann Arbor. 269 pp. 1948. S. D. Koch, The Eragrostis 
pectinacea-pilosa complex in North and Central America. 
(Gramineae-Eragrostoideae), Illinois Biological Monographs 48; I-XI 
+ 74 pp. Univ. of Illinois Press. Urbana. 1974. 

Plants annual or perennial, caespitose, stoloniferous, or rarely rhizomatous. Inflores- 
cence an open or contracted panicle; spikelets laterally compressed; florets 2-many; 
glumes short, keeled, 1-nerved; lemmas ovate, blunt to acute, 3-nerved, the nerves 
usually prominent; paleas at least half as long as the lemmas, with prominent keels; 
disarticulation usually sequential from the base upward, the glumes dropping from the 
rachilla first, followed by the lemmas; paleas usually remaining on the persistent rachilla; 
anthers 2-3; caryopsis free from the lemma and palea, oblong or elliptical, brown or tan, 
translucent, usually faintly striate. Some species have spikelets that regularly disar- 
ticulate above the glumes and between the florets, and a few species disarticulate in 
either fashion. 



208 FIELDIANA: BOTANY 

Eragrostis is a large genus, common in warm temperate and tropical 
climates of the world. The genus contains much diversity, and various 
segregate genera have been proposed. The awnless spikelets with 
prominently 3-nerved lemmas and the peculiar type of disarticulation 
are good marks of recognition. Many of the species are weedy, and 
only a very few perennial species (e.g. , Eragrostis curvula) have value 
for forage. The genus is related to Triplasis, Leptochloa, Eleusine, 
and Dactyloctenium among the Costa Rican grasses. (Chloridoideae: 
Eragrosteae.) 

KEY TO SPECIES OF Eragrostis 

la. Plants extensively stoloniferous, rooting at nodes, forming flat mats on moist 

soil E. hypnoides 

Ib. Plants caespitose, not stoloniferous; culms usually erect or ascending 2 

2a. Keels of paleas prominently ciliate with papillose-based hairs visible from 

outside of spikelets 3 

2b. Keels of paleas not long-ciliate, mostly scabrous 5 

3a. Panicles densely cylindrical, at least 10 x longer than wide; spikelets subsessile, 
pedicels much shorter than spikelets; pulvini of branches lacking long hairs 

E. ciliaris 

3b. Panicles open, rachis visible, length less than 5 x width; pedicels short or long . 4 
4a. Panicles open and delicate; pulvini of panicle branches bearing long, silky 

hairs; plants not viscid E. tenella 

4b. Panicles rather densely flowered, not delicate; pulvini of branches lacking 
long hairs; plants usually viscid, particles of soil adhering to sticky areas 

E. viscosa 

5a. Ligule a membrane E. glomerata 

5b. Ligule a dense row of minute hairs 6 

6a. Plants forming large dense clumps with numerous very elongated (to 100 cm.) 
arching and drooping basal leaf blades that terminate in an elongated thread- 
like apex; basal sheaths closely overlapping, copiously appressed-hispid; cul- 
tivated perennial E. curvula 

6b. Plants in small tufts, lacking elongated basal leaves; wild plants, annuals or 

perennials 7 

7a. Lemmas acuminate, strongly keeled, midnerve projecting as scabrous ridge; 

length of lemma usually 4-6 x folded width 8 

7b. Lemmas acute, rounded on the back or slightly keeled but without projecting 
midrib; length of lemmas less than 4 x folded width 10 

8a. Pulvini of panicle branches bearing conspicuous tufts of long hairs 9 

8b. Pulvini of panicle branches lacking tufts of long hairs; lemmas 3.4-4.0 mm. 
long, 3-5-nerved; panicle branches very short, densely covered with overlap- 
ping spikelets E. simpliciflora 

9a. Panicle dense, longest branches up to 5 cm. long, bearing spikelets to their bases; 

spikelets subsessile, overlapping E. maypurensis 

9b. Panicle large and open, the branches up to 9 cm. long, naked near their bases; 



BURGER: FLORA COSTARICENSIS 209 

spikelets borne on pedicels up to 5 mm. long, not concealing rachis or branches 

E. acutiflora 
lOa. Spikelets linear, 6-9 x longer than wide, deep leaden gray or blackish; glumes 

minute, the second less than 1 mm. long E. tenuifolia 

lOb. Spikelets narrowly ovate or linear, less than 5 x longer than wide, greenish, 

light gray, stramineous, or purplish; glumes more than 1 mm. long 11 

lla. Panicle narrow, dense, 6 or more x longer than wide, branches erect, densely 
flowered; larger leaf blades up to 60 cm. long; coarse, harsh perennial seashore 

grasses; Pacific Coast E. prolifera 

lib. Panicles open, pyramidal, 2-3 x longer than wide; branches spreading; leaf blades 

usually less than 20 cm. long; small annual grasses of various habitats 12 

12a. Mature spikelets 2-3 mm. wide; keels of sheaths often bearing pustulose 

glands E. cilianensis 

12b. Mature spikelets 1.5 mm. or less wide; sheaths lacking pustulose glands on 

keels 13 

13a. Spikelets closely appressed to primary branches of panicle E. pectinacea 

13b. Spikelets at maturity mostly diverging strongly from branches 14 

14a. Spikelets slender, delicate, ca. 1 mm. wide; pedicels of lateral spikelets 1- 
several x as long as spikelets E. pilosa 

14b. Spikelets linear to narrowly ovate, 1.5 mm. or more wide; pedicels of lateral 

spikelets mostly equal in length to or shorter than spikelets 15 

15a. Caryopsis oblong, truncate, with broad, shallow groove on side opposite embryo; 

spikelets 2-3 x longer than wide, often purplish E. mexicana 

15b. Caryopsis elliptic-oblong, with rounded ends, cylindrical, not grooved; spikelets 

3.5-4.5 x longer than wide, green or stramineous E. tephrosanthos 

Eragrostis acutiflora (H.B.K.) Nees, Agrost. Bras. 501. 1829. Poa 
acutiftora H.B.K. , Nov. Gen. & Sp. PI. 1:161. 1816. 

Caespitose perennial, in small, dense tufts; culms erect to ascending, 35-70 cm. long, 
mostly unbranched; internodes 1.5-2.0 mm. thick, hollow, glabrous; nodes glabrous; 
sheaths glabrous except at the long-ciliate throat; ligule a minute ciliolate membrane, ca. 
0.2 mm. long; leaf blades 6-25 cm. long, 2-4 mm. wide, mostly folded or involute, gla- 
brous beneath, more or less pubescent with scattered long weak hairs on the ridged, 
scaberulous upper surface. Inflorescence solitary, terminal; panicle ovoid 2:1, 17-28 cm. 
long, ca. half as wide, open, the branches solitary, the longest one up to 10 cm. long; 
pulvini silky-ciliate with conspicuous hairs; spikelets more or less appressed along the 
primary branches; pedicels of lateral spikelets up to 5 mm. long. Spikelets oblong 3-6:1, 
5-10 mm. long, with 9-17 florets; the bracts strongly flattened and keeled, usually purple 
near the keels and whitish near the margins, the spikelets thus appearing bicolored; 
disarticulation from the base upward, the glumes dropping, followed by the lemmas, the 
paleas persistent on the flexuous rachilla; the florets rarely disarticulating individually; 
glumes ovate 4-5:1 as folded, the keels scabrous; first glume 0.9-1.5 mm. long; 1-nerved; 
second glume similar but wider, 1.3-1.9 mm. long; lower lemmas 2.0-2.2 mm. long, ovate 
5:1, the margins nearly straight, surface smooth or scaberulous; palea ca. three-fourths 
as long as the lemma, the keels bowed-out, short-scabrous; anthers 2, purple, 0.3 mm. 
long; caryopsis ca. 0.7 mm. long, hah 9 as wide, amber. Chromosome number n - 20 from 
a Venezuelan specimen. 



210 FIELDIANA: BOTANY 

Ocean beaches, open roadsides, cultivated fields, savannas, sea level 
to 450 m. elevation; Guanacaste; General Valley; both coasts. June to 
December. Southern Mexico to Panama, Brazil, and Bolivia; Trinidad. 

Eragrostis cilianensis (All.) Lutati, Malpighia 18:386. 1904. Poa 
cilianensis Allioni, Fl. Fed. 2:246. 1785. Eragrostis megastachya 
(Koel.) Link, Hort. Berol. 1:187. 1827. Figure 70. 

Caespitose annual; plants erect, sprawling, or decumbent; culms simple or branched 
from the lower nodes, the internodes glabrous, up to 2 mm. thick, with a thick wall, the 
lumen usually filled with pith; nodes glabrous, enlarged; sheaths longer or shorter than 
the internodes, glabrous except for elongated silky auricular hairs; flat, circular pus- 
tulose glands usually present just above the nodes or more commonly on the keel of the 
sheath; ligule a dense ring of white hairs, ca. 0.5 mm. long; leaf blades 5-20 cm. long, up 
to 7 mm. wide, glabrous, sometimes bearing pustulose glands on their lower margins. 
Inflorescences terminal or sometimes axillary, 6-16 cm. long, 2-8.5 cm. wide, ovoid, 
dense to open, greenish to leaden color, becoming stramineous when dry, with numerous 
spikelets. Spikelets 6-20 mm. long, linear or ovate, 2-4 mm. wide, with 12-40 florets; 
disarticulation usually sequential from the base upward, the glumes dropping first, 
followed by the lemmas, the paleas remaining on the rachilla; occasionally disarticulating 
between the florets; glumes strongly keeled, scabrous on the keel, the first 1-nerved, 
1.2-2.0 mm. long; second similar but broader, sometimes weakly 3-nerved, 1.2-2.6 mm. 
long; lower lemmas 2.0-2.8 mm. long, ovate, rather blunt, the 3 nerves conspicuous, back 
sometimes scabrid near the tip; palea ca. 0.6 as long as its lemma, scabrous on the keels, 
bidentate at the tip; anthers 3, yellow, 0.3-0.5 mm. long; styles 2; caryopsis broadly 
ellipsoid, 0.6-0.7 mm. long and more than two-thirds as wide, reddish brown. 

Rare in Costa Rica; known from Finca la Pacifica, Canas, Hacienda 
Tenorio, and Puntarenas. June to October. Pastures and disturbed 
open ground at low elevations. This introduced European species is 
very common in warmer parts of the United States, extending south- 
ward to northwestern Costa Rica; Cuba and Bermuda; to temperate 
South America (Argentina). 

Like most species of Eragrostis, this one has spikelets that first 
appear with only the basal florets visible and continue to grow and 
develop more florets at the apex for some time. Because of this, young 
panicles with juvenile spikelets appear very different from mature 
ones. The tendency to shed glumes and lower lemmas is not as strong 
in this species as in some others, and the rachilla occasionally disar- 
ticulates. The plants have a fetid odor when fresh, presumably because 
of the secretions of the pustulose glands. In Central American mate- 
rial, these glands appear to be restricted largely to the keels of the 
sheaths, whereas in specimens from the temperate zone, they are 
much more abundant and occur on the sheath bases, panicle branches, 
and keels of the lemmas. 




FIG. 70. Eragrostis cilianensis. Blooming plant, young and mature spikelets, segment 
of rachilla with two florets and a persistent palea. 



211 



212 FIELDIANA: BOTANY 

Eragrostis ciliaris (L.) R. Br. in Tuckey, Narr. Exp. Congo 478. 
1818. Poa ciliaris L., Syst. Nat. ed. 10. 2:875. 1759. Figure 71. 

Caespitose annual in small tufts; culms 3-40 (65) cm. long, erect, ascending, or decum- 
bent, branching from the base or lower nodes; internodes less than 1 mm. thick, hollow, 
glabrous; nodes glabrous; sheaths glabrous except papillose-pilose on the overlapping 
margin; auricular hairs abundant, to 4 mm. long, silky; ligule a minute ciliate rim, 0.2-0.5 
mm. long. Peduncle exserted up to 11 cm.; panicle solitary, terminal on the main culm 
or occasionally on leafy branches, 4-14 cm. long, 3-8 mm. thick, densely cylindrical, 
spikelike, more than 10 x longer than wide; branches mostly less than 1 cm. long, 
densely flowered to their bases, the lower ones sometimes remote from the main body of 
the panicle; axils of the branches glabrous; pedicels erect, 0.2-0.6 mm. long, shorter than 
the spikelets. Spikelets numerous, densely clothing the branches, 2.2-2.5 mm. long, 
mostly 6-9-flowered, disarticulating above the glumes and between the florets or, rarely, 
the rachilla remaining intact and the lemmas dropping; first glume 0.8-1.2 mm. long, 
1-nerved, ovate, acute; second glume similar, 1.0-1.3 mm. long, the keels sometimes 
ciliolate or scabrous; lower lemmas 1.0-1.3 mm. long, ovate, acute, the internerves 
scabrid; palea about equal to the lemma, papillose-ciliate on the keels with divergent 
straight hairs to 0.6 mm. long; anthers 3, purplish, ca. 0.2 mm. long; caryopsis elliptical 
2:1, amber, 0.5 mm. long. Chromosome number n = 10, 20. 

Common on weedy open ground and disturbed soils, from sea level 
to 1,500 m. elevation; most common at low elevations. Blooming ap- 
parently all year. Florida and Gulf Coast of the United States to north- 
ern Mexico and southward to Peru and Brazil. Apparently introduced 
from the tropics of the Old World. 

Eragrostis curvula (Schrad.) Nees, Fl. Afr. Austral. 1:397. 1841. 
Poa curvula Schrad., Goett. Anz. Ges. Wiss. 3:2073. 1821. 

Long-lived perennial, densely caespitose and forming large circular clumps with very 
numerous, densely crowded leafy innovations with elongated drooping blades; culms 
unbranched, up to 150 cm. long, arching, the inflorescence drooping; internodes gla- 
brous, up to 2.5 mm. thick, solid, the lumen filled with pith; nodes glabrous; foliage 
mostly basal, the basal leaf sheaths densely overlapping, their surfaces covered with flat 
longitudinal ridges, copiously appressed-hispid with hairs arising in the grooves between 
the ridges; blades of the basal leaves flat or involute, very elongated, up to 1 m. long, ca. 
2 mm. wide, tapering to an elongated caudate tip, the aspect of the clump fountain-like 
from the numerous drooping and trailing basal leaf blades; ligule a dense fringe of short 
hairs, ca. 0.5 mm. long; a tuft of elongated silky hairs at the throat and behind the ligule. 
Peduncle long-exserted, silky-bearded at the apex; panicle solitary, terminal, usually 
17-23 cm. long, open, ovoid-cylindrical, the length 3-7 x the width; pulvini silky-bearded; 
branches mostly paired, naked near the base, the spikelets clustered on short secondary 
branches and appressed along the primary branches; lateral pedicels usually shorter 
than the spikelets. Spikelets leaden-gray, 4-7.5 mm. long, usually with 5-9 florets; disar- 
ti culation either sequential from the base upward, the glumes falling first, followed by 
the lemmas, the paleas usually persistent on the intact rachilla; or in some cases, the 
rachilla disarticulating between the florets; rachilla internodes ciliate at the tip; glumes 
1-nerved, the first 1.5-2.1 mm. long, narrowly triangular, the second similar but wider, 
2.0-2.5 mm. long; lower lemmas 2.4-3.4 mm. long, oblong-ovate, acute, the nerves not 




FIG. 71. Eragrostis species. E. ciliaris: A, panicle; B, spikelet; C, floret showing 
ciliate palea; E. tenella: D, blooming plant. 



213 



214 FIELDIANA: BOTANY 

conspicuous; palea nearly equal to its lemma; anthers 3, purple, 1.1-1.6 mm. long; 
caryopsis elliptical, amber, 1.4-1.5 mm. long, flattened on the back; embryo dark, ca. half 
as long as the grain. A wide variety of chromosome numbers has been reported for the 
group. 

This African species has been widely cultivated in the southern half 
of the United States for forage, stabilization of embankments, and 
revegetation of abandoned lands. It is also cultivated in temperate 
South America (Uruguay and Argentina). To a limited extent, it is 
currently being cultivated as an ornamental in the cities of the Meseta 
Central. Our only specimen with inflorescences was obtained from the 
campus of the University of Costa Rica. Several related forms or 
species occur in Africa and are poorly separable from E. curvula. 
Because of the drooping leaf blades, it has been called "weeping love 
grass" in English and Pasto lloron in Spanish. 

Eragrostis glomerata (Walt.) L. H. Dewey, Contr. U.S. Natl. 
Herb. 2:543. 1894. Poa glomerata Walt., Fl. Carol. 80. 1788. Dian- 
drochloa glomerata (Walt.) Burk., Fl. Illus. Entre Rios 168. 1969. Col. 
Cient. del I.N.T.A. VI, II. Figure 72. 

Caespitose annual; culms erect, 25-90 cm. long, branching from the lower and middle 
nodes; prophylla 3.5-6.0 cm. long, bidentate at the tip; culm internodes 1.5-4.0 mm. 
thick, glabrous, hard, very thick-walled, with a small lumen that is empty or filled with 
loose sheets of parenchyma; sheaths glabrous, shorter or longer than the internodes; 
ligule an erose membrane, 0.4-0.5 mm. long; leaf blades flat, up to 25 cm. long and 7 mm. 
wide, glabrous or scaberulous above. Peduncle included or exserted; inflorescence a 
solitary panicle terminal on the main culm or on leafy branches; panicles congested, 
densely cylindrical, 13-25 cm. long, 2-3 cm. thick; branches fascicled, erect to ascending, 
densely flowered to their bases; spikelets crowded, overlapping, the pedicels usually 
much shorter than the spikelets, erect. Spikelets laterally compressed, 2.8-3.4 mm. long, 
whitish, disarticulating above the glumes and between the florets; glumes ovate, acute, 
scabrous on the keels, the first 0.7-0.9 mm. long, the second slightly longer than the first; 
florets usually 8-9; .lemmas 1.0-1.1 mm. long, ovate, acute, the nerves conspicuous, 
green, the internerves whitish or translucent; palea slightly shorter than its lemma, 
ciliolate at the tip; anthers 2, white, 0.2 mm. long; caryopsis obovoid 3:2, ca. 0.4 mm. 
long, amber. Chromosome number n = 10 from a Costa Rican specimen. 

Disturbed open areas, rare in Costa Rica. November and December. 
The only two specimens known from Costa Rica are from the Cariari 
Club and La Guacima. Southeastern United States to northwestern 
South America, southward to Bolivia and Argentina. 

Eragrostis hypnoides (Lam.) B.S.P., Prelim. Cat. N.Y. 69. 1888. 
Poa hypnoides Lam., Tabl. Encycl. 1:185. 1791. Figure 73. 

Diminutive creeping annual, forming flat circular patches; stolons much-branched, 
rooting at the nodes; flowering culms fascicled from the rooted nodes, usually ascending, 
less than 10 cm. long; nodes glabrous; internodes glabrous, less than 0.5 mm. thick, 



If 

V ':\i ?! 




\\ 



FIG. 72. Eragrostis species. E. glomerata: A, panicle; B, group of spikelets; C, leaf 
base and ligule; E. prolifera: D, disarticulating spikelet showing persistent paleas. 



215 



216 



FIELDIANA: BOTANY 




FIG. 73. Eragrostis hypnoides. Blooming plant, portion of a spikelet showing one 
floret, persistent paleas, one caryopsis. 

hollow; sheaths glabrous except for the finely ciliate overlapping margin; ligule a dense 
row of minute hairs, ca. 0.5 mm. long; leaf blades 4-30 mm. long, 1.0-1.5 mm. wide, flat 
or folded, the lower surface glabrous, the upper finely papillose-puberulent. Inflores- 
cences numerous, on short leafy culms arising from the stolons, rather dense, broadly 
ovoid, 2-4 cm. long and nearly as wide; branches very short, bearing 1-few spikelets; 
lateral pedicels less than 1 mm. long. Spikelets compressed and keeled, linear, 8-14 mm. 
long, up to 3 mm. wide, with 15-32 florets; disarticulation sequential from the base 
upward, the glumes falling first, followed by the lemmas, the paleas remaining on the 



BURGER: FLORA COSTARICENSIS 217 

intact rachilla; glumes 1-nerved, narrowly ovate, acute, scabrous on the keel, the first 
0.6-0.8 mm. long, the second 0.9-1.2 mm. long; lower lemmas narrowly ovate or trullate, 
1.8-2.2 mm. long, strongly 3-nerved, glabrous; palea ca. half as long as its lemma; 
anthers 2, white, ca. 0.2 mm. long; caryopsis elliptical, 0.4-0.5 mm. long and ca. half as 
wide. 

Sand and mud bars along streams, flat wet beach areas around lakes; 
apparently rare in Costa Rica. None of our collections is recent. Tucur- 
rique, San Jose. Throughout its range, this species occupies moist, 
recently exposed shores. Suitable habitats for its establishment may 
be rare in Costa Rica. Nearly all of the United States, southward 
through Mexico, Central America to Argentina. 

This delicate little creeping grass fruits so abundantly that at 
maturity, the entire plant consists primarily of the elongated spikelets, 
which probably carry on the majority of the photosynthesis, since 
foliage is so sparse. 

Eragrostis maypurensis (H.B.K.) Steud., Syn. PL Glum. 1:276. 
1854. Poa maypurensis H.B.K., Nov. Gen. & Sp. 1:161. 1816. Figure 
74. 

Duration indefinite, probably annual; plants caespitose, erect to prostrate, culms 15-70 
cm. long, mostly unbranched or in larger plants with a few branches; internodes 0.5-1.0 
mm. thick, hollow, glabrous; nodes glabrous; sheaths about as long as the internodes, 
varying from nearly glabrous to densely papillose-pilose on the back and collar; auricles 
usually long-ciliate with hairs to 4 mm. long; ligule a minute stiff fringe of hairs, 0.2-0.3 
mm. long; leaf blades 4-15 cm. long, up to 4 mm. wide, densely papillose-pilose to nearly 
glabrous on the upper surface or both sides. Peduncle exserted up to 15 cm., glabrous to 
densely papillose-pilose; inflorescence a solitary terminal panicle, 4-20 cm. long, open, 
narrowly pyramidal, the branches solitary, up to 4.5 cm. long, simple or rebranched; 
rachis and branches from heavily pilose to nearly glabrous; axils of main panicle branches 
bearing tufts of long silky hairs; spikelets rather densely clustered and divergent along 
the branches; pedicels mostly 0.2-0.5 mm. long. Spikelets oblong, strongly keeled and 
compressed, 7-12 mm. long, ca. 3-4 x longer than broad, glabrous, stramineous to 
reddish, with up to 27 florets; disarticulation from the base upward, the glumes and then 
the lemmas dropping, leaving the paleas on the persistent rachilla; glumes 1-nerved, 
strongly keeled, scabrous on the keel; first glume 1.5-2.5 mm. long, 1-nerved, narrowly 
triangular, usually acuminate; second glume similar, 1.7-2.5 mm. long; lower florets 
1.9-2.7 mm. long, the lemmas ovate 2:1, caudate, the nerves conspicuous, usually green; 
keel scabrous; palea ca. two-thirds as long, bowed out above the base; the keels scab- 
rous; anthers usually 2, purple, 0.2 mm. long; caryopsis oblong, reddish, ca. 0.5 mm. 
long. Chromosome number n = 10 from Costa Rican and South American specimens. 

Dry savannas, pastures, roadsides; common on the savannas of 
northwestern Guanacaste; dryer western parts of the Meseta Central; 
Buenos Aires; Boruca. Elevations to 600 m. Baja California and South- 
ern Mexico to Bolivia and Brazil. This species is extremely variable in 
stature and pubescence. 



218 



FIELDIANA: BOTANY 





FIG. 74. Eragrostis species. E. maypurensis: A, group of spikelets; E. simpliciflora: 
B, panicle; C, spikelet. 



Eragrostis mexicana (Hornem.) Link, Hort. Berol. 1:190. 1827. 
Poa mexicana Hornem., Hort. Hafn. 2:953. 1815. Eragrostis limbata 
Fourn., Mex. PL 2:116. 1881. Figure 75. 

Plants caespitose, annual, erect or the lower nodes of the culms geniculate, up to 80 
cm. tall but usually much smaller; culms unbranched or branched from the lower nodes, 
ca. 1 mm. thick; internodes glabrous, hollow or the lumen filled with pith; nodes gla- 
brous, dark; sheaths keeled, mostly shorter than the internodes, glabrous or with a few 
papillose-based silky hairs on the overlapping margins; auricles and collar densely 
bearded with elongated silky hairs; ligule a minute membrane, densely ciliate with short 
white hairs, in total 0.2-0.5 mm. long; leaf blades flat or somewhat involute, 10-25 cm. 
long, 3-9 mm. wide, smooth beneath, minutely scaberulous above, occasionally with a 
few delicate elongated hairs on the upper surface near the base. Inflorescences solitary, 
terminal; panicle open but with numerous spikelets, ovoid, 2-3 x longer than wide, 15-40 



BURGER: FLORA COSTARICENSIS 



219 





FIG. 75. Eragrostis mexicana. Portion of a panicle, portion of a spikelet showing a 
floret and two persistent paleas. 

cm. long, the longest branch ca. 12 cm. long; spikelets strongly divergent from the 
primary or secondary branches, the stiff, flexuous pedicels longer or shorter than the 
spikelets. Spikelets laterally compressed, 4.5-6.0 mm. long, 2-3 x longer than wide, 
greenish or purplish; disarticulation sequential from the base upward, the glumes drop- 
ping first, followed by the lemmas, the paleas remaining on the intact rachilla; glumes 
1-nerved, strongly keeled, scabrous on the keels, the first narrowly ovate, 1.6-1.9 mm. 
long, acuminate; second glume similar but slightly wider, 1.7-2.2 mm. long; florets usu- 
ally 6-8; lower lemmas 1.9-2.2 mm. long, ovate 3:1 as folded, the 3 nerves green, con- 
spicuous, tip acute; tip and sometimes the margins scaberulous; palea ca. three-fourths 
as long as its lemma; anthers 3, purplish, ca. 0.4 mm. long; caryopsis oblong, the ends 
truncate, 0.6-0.7 mm. long, dark reddish brown, with a longitudinal groove on the side 
opposite the embryo. Chromosome number n = 30 from Costa Rican specimens. 

Occasional in coffee and sugarcane plantations, on roadsides and 
streets, and in gardens. Occasional in the Meseta Central, at eleva- 
tions of 500 to 1,500 m.; Turrialba; Zarcero. June to February. Arizona 
and New Mexico to Costa Rica; Venezuela and Brazil. 

Eragrostis pectinacea (Michx.) Steud., Syn. PL Glum. 1:272. 1854. 
Poa pectinacea Michx., Fl. Bor. Amer. 1:69. 1803. Figure 76. 

Caespitose annual, 10-60 cm. tall, mostly in small tufts; culms erect to spreading, 
branching from the base and lower nodes; prophyllum to 3 cm. long; internodes glabrous, 
either solid, with pith filling the lumen, or partly hollow; nodes glabrous, dark; sheaths 
mostly shorter than the internodes, glabrous except for a tuft of elongated auricular 
hairs; ligule a dense line of minute hairs, 0.2-0.5 mm. long; leaf blades 2-15 cm. long, 
1.0-4.5 mm. wide, flat or involute, glabrous. Inflorescences solitary, terminal on the 
main culm or leafy branches; panicles 5-25 cm. long and ca. half as wide; branches 
solitary or paired, simple or occasionally branched, naked near the base, the spikelets 
closely appressed to the branches, grayish. Spikelets laterally compressed, linear, 4.5-11 
mm. long, with 6-22 florets; disarticulation sequential from the base upward, the glumes 
dropping first, followed by the lemmas, the paleas remaining on the persistent rachilla; 
glumes 1-nerved, the first subulate, 0.5-1.1 mm. long, the second narrowly triangular, 
1.1-1.7 mm. long; lemmas grayish or with a purplish band near the apex, ovate 4:1 as 
folded, acute, the nerves evident; palea at least three-fourths as long as its lemma; lower 




FIG. 76. Eragrostis pectinacea. Blooming plant, partially disarticulated spikelet with 
persistent lower paleas. 



220 



BURGER: FLORA COSTARICENSIS 221 

lemmas 1.7-1.9 mm. long; anthers 3, purple, ca. 0.3 mm. long; caryopsis elliptical, 0.7 
mm. long, ca. half as wide, amber. 

Roadsides, railroad embankments, cultivated fields, disturbed open 
areas generally; occasional at elevations from sea level to 800 m. , both 
Pacific and Caribbean slopes. June to March. Possibly introduced from 
the United States. Northern United States to Panama; West Indies; 
introduced in Argentina. 

Eragrostis pilosa (L.) Beauv., Ess. Nouv. Agrost. 71, 162, 175. 
1812. Poa pilosa L., Sp. PI. 68. 1753. 

Caespitose annual in small tufts; plants 15-45 cm. tall; culms erect, branched from the 
base and lower nodes; internodes glabrous, hollow, ca. 0.5 mm. thick; nodes glabrous, 
dark; sheaths glabrous except for a tuft of long, stiff auricular hairs; leaf blades flat or 
involute, 5-15 cm. long, 2-3 mm. wide, glabrous beneath, scaberulous above. Inflores- 
cences terminal on the main culm or on leafy branches; panicles ovoid 2:1, open and 
delicate; branches spreading; pedicels strongly divergent, capillary, flexuous, longer 
than the spikelets. Spikelets grayish, linear, laterally compressed, 2-6 mm. long; disar- 
ticulation sequential from the base upward, the glumes dropping first, followed by the 
lemmas and often the paleas; first glume 0.8-1.0 mm. long, 1-nerved, narrowly ovate, 
acute, the keel scabrid; second glume similar but wider, 1.2-1.6 mm. long; florets usually 
3-8; lemmas 1.2-1.6 mm. long, ovate, rather faintly 3-nerved, sometimes somewhat 
scabrid toward the tip; palea at least three-fourths as long as its lemma; anthers 3, 
purple, 0.2-0.3 mm. long; caryopsis elliptical 2:1, brown, ca. 0.7 mm. long. 

Known in Central America only by the following specimen: 
Guanacaste, dry savanna, 21 km. NW of Liberia, 75 m. elevation, Pohl 
& Calderdn 12167, 31 July 1966. This introduced European species is 
widely established in the United States and has previously been re- 
ported as far south as southern Mexico. Caribbean Islands. 

Eragrostis prolifera (Swartz) Steud., Syn. PI. Glum. 1:278. 1854. 
Poa prolifera Swartz, Nov. Gen. & Sp. PI. Prod. 27. 1788. Eragrostis 
domingensis (Pers.) Steud., Syn. PI. Glum. 1:278. 1854. Poa 
domingensis Pers. , Syn. PL 88. 1805. Figure 72. 

Caespitose perennial, in dense, hard clumps; culms erect or ascending, mostly un- 
branched, to 2 m. long; internodes glabrous, up to 4 mm. thick, hard, very thick-walled, 
with a small lumen; nodes glabrous; lower sheaths mostly overlapping; sheaths glabrous; 
ligule a minute ciliate rim, 0.3-0.5 mm. long; leaf blades harsh, up to 60 cm. long, to 5 
mm. wide, flat or involute, glabrous except for the occasional presence of a few long cilia 
at the throat or at the base of the blade; lower surface glabrous; upper surface minutely 
scaberulous, apex tapering to an elongate scabrous caudate tip. Inflorescence a solitary 
terminal panicle; peduncle glabrous, to 40 cm. long; panicle up to 44 cm. long, usually 3 
cm. or less thick; branches solitary or fascicled of various lengths together, the longest 9 
cm. long, strict, erect, densely flowered to their bases; primary branches bearing 
numerous erect short secondary branches; spikelets borne on erect pedicels much 
shorter than the spikelets. Spikelets oblong, stramineous when mature, 4.5-11.5 mm. 
long, 1.2-2.0 mm. wide; disarticulation sequential from the base upward, the glumes first 



222 FIELDIANA: BOTANY 

dropping, followed by the lemmas, the paleas persistent on the persistent flexuous 
rachilla; first glume 1.2 mm. long, subulate, 1-nerved, scabrous on the keel; second 
glume narrowly ovate, 1-nerved, 1.2-1.5 mm. long; florets 8-24; lower lemmas 1.3-1.5 
mm. long, ovate, acute, plainly 3-nerved, keeled toward the apex; palea about equal to 
the lemma; anthers 2, purple, 0.5-0.6 mm. long; caryopsis ovoid, ca. 0.8 mm. long and 
half as wide, amber, minutely striate. 

Salinas and sandy beaches of the Pacific; Puerto Castillo, Puerto 
Soley, Chomes, Puntarenas. October to January. Southern Mexico to 
Colombia. 

Eragrostis simpliciflora (Presl) Steud., Syn. PI. Glum. 1:278. 1854. 
Megastachya simpliciflora Presl, Rel. Haenk. 1:283. 1830. Figure 74. 

Duration indefinite, probably annual; plants caespitose, the culms erect to prostrate, 
10-30 cm. long, branching freely from the base and also from the lower and middle nodes; 
prophylla 9-15 mm. long; internodes 0.7-1.0 mm. thick, hollow, glabrous; sheaths mostly 
overlapping, glabrous except for auricular hairs up to 4 mm. long, keeled; ligule a row of 
minute stiff hairs, to 0.1 mm. long; leaf blades up to 15 cm. long, 2-4 mm. wide, more or 
less involute, the upper surface ridged, scaberulous, bearing scattered elongate weak 
hairs. Panicles terminal and axillary, mostly 4-8 cm. long, ovoid to narrowly pyramidal, 
the few branches stiffly spreading or ascending, up to 4 cm. long, bearing few spikelets 
that are appressed to the branches or divergent. Spikelets purplish or stramineous, 
linear, 9-24 mm. long, very flattened and keeled, subsessile along the branches, the 
lateral pedicels 0.2-0.5 mm. long; glumes and lemmas at maturity dropping from the 
flexuous rachilla, the paleas persistent; rachilla only very tardily disarticulating; first 
glume ovate, acute, 1-nerved, 1.6-2.0 mm. long; second glume similar, 2.1-2.5 mm. long; 
florets 12-24; lower lemmas 3.4-3.8 mm. long, ovate 5:1 as folded, acuminate, usually 
3-nerved, or with a fainter pair of secondary nerves just inside of the principal lateral 
nerves; surface minutely scabrid; keel scabrous; paleas ca. two-thirds as long as the 
lemmas, bowed outward above the base, the scabrous-ciliate keels prominent, the area 
between the keels deeply infolded; anthers purplish, 0.3 mm. long; caryopsis oval 2:1, 
0.8-1.0 mm. long. Chromosome number n = 20 from a Costa Rican specimen. 

Open dry areas in full sun, roadsides, pastures, savannas; western 
Meseta Central (Guadalupe, Nuestro Amo, San Pedro de Poas); Hda. 
Las Animas, Guanacaste. December to March. Southern Mexico to 
Panama. 

Eragrostis tenella (L.) Beauv. ex R. & S., Syst. Veg. 2:576. 1817. 
Poa tenella L., Sp. PL 69. 1753. Poa amabilis L., Sp. PL 68. 1753. 
Eragrostis amabilis (L.) Wight & Arn. ex Hook. & Am., Bot. 
Beechey Voy. 251. 1838. For discussion of the nomenclature of this 
species, See N. L. Bor, 1960. The Grasses of Burma, Ceylon, India, 
and Pakistan, pp. 513-514. 1960. Figure 71. 

Delicate sprawling caespitose annual in small tufts; culms 5-25 cm. long, branching 
from the base; internodes glabrous, less than 0.5 mm. thick, hollow or pithy; nodes 
glabrous; sheaths glabrous except for papillose pilosity on the overlapping margins; 



BURGER: FLORA COSTARICENSIS 223 

ligule a dense row of minute stiff erect hairs; leaf blades flat, mostly 3-5 cm. long, 2-3 
mm. wide, glabrous, scabrous on the margins; collar and auricles beset with straight 
papillose-based hairs up to 4 mm. long. Peduncle exserted to 4 cm.; inflorescence a 
solitary, terminal, open cylindrical panicle, 1.5-9 cm. long, up to 3 x longer than wide; 
rachis bearing silky hairs on the pulvini and scattered flat glandular spots on the 
internodes; branches spreading; at least some of the pedicels 1-3 x as long as the 
spikelets. Spikelets whitish or purple, oblong, mostly 1.7-2.0 mm. long, mostly with 4-6 
florets; disarticulation above the glumes and between the florets; first glume 0.5-0.6 mm. 
long, ovate, acute, 1-nerved; second glume similar, 0.7-0.8 mm. long; lemmas mostly 
0.8-1.0 mm. long, oblong, usually blunt; nerves conspicuous, the lateral ones submargi- 
nal, converging only slightly toward the blunt apex; internerves scabrid; palea nearly as 
long as its lemma, the keels prominently ciliate with strongly divergent papillose-based 
straight hairs up to 0.3 mm. long, these conspicuous on the spikelets; anthers 3, purplish, 
0.2 mm. long; caryopsis elliptic 2:1, clear reddish amber colored, 0.5 mm. long. 

Casual weed in open areas, mostly near the Caribbean; Limon, 
Limon airport; Isla Uvita; Puerto Viejo (S of Cahuita); Turrialba. June 
to September. Introduced from the Old World. Southeastern United 
States to Texas; west coast of Mexico; Central America to Panama and 
tropical South America; West Indies. 

Eragrostis tenuifolia (A. Rich.) Hochst. ex Steud., Syn. PI. Glum. 
1:268. 1854. Poa tenuifolia A. Rich., Tent. Fl. Abyss. 2:425. 1851. 
Figure 77. 

Caespitose perennial; clumps dense, hard; culms 30-75 cm. long, erect to prostrate, 
unbranched or branched from the lower nodes; internodes hollow, glabrous; nodes gla- 
brous; prophylla up to 2.5 cm. long; sheaths about as long as the lower internodes, 
strongly compressed and keeled, glabrous, the overlapping margin softly pilose; throat 
pilose with hairs to 2 mm. long; ligule a dense line of minute hairs, to 0.25 mm. long; leaf 
blades flat or folded, up to 20 cm. long, 2-3 mm. wide. Peduncle exserted up to 18 cm., 
glabrous; inflorescence a solitary terminal panicle, 5-19 cm. long, narrowly pyramidal, 
very open; rachis angular, grooved, scabrous on the angles, the pulvini prominent, 
strongly ciliate with fine silky hairs to 2 mm. long; branches solitary, strongly divergent, 
thin and stiff; pedicels strongly divergent from the branches, the lateral ones 3-13 mm. 
long, the terminal ones longer. Spikelets linear, leaden-colored, 6-14 mm. long, 1.5-2.0 
mm. wide, laterally compressed but not strongly keeled; disarticulation sequential from 
the base upward, the glumes dropping first, followed by the lemmas, the paleas remain- 
ing on the flexuous persistent rachilla; glumes much reduced, subulate, the first 0.3-0.6 
mm. long, separated from the second by a visible internode; second glume similar, 
0.5-1.0 mm. long; florets 6-15; lemmas ovate 4:1 as folded, acute, faintly nerved; palea 
more than three-fourths as long as the lemma, bowed out above the base; anthers 3, 
whitish, 0.4-0.5 mm. long; flowers apparently cleistogamous, the anthers remaining 
tangled with the style branches and not exserted; caryopsis oblong, 0.6-1.0 mm. long, 
blunt, amber, about half as wide as long. Chromosome number n = 20 from a Costa 
Rican specimen. 

Soccer fields, roadsides, streets, disturbed open areas generally; 
very common in the Meseta Central, but now known from La Cruz on 




B 



FIG. 77. Eragrostis tenuifolia. A, panicle; B, spikelet; C, floret. 
224 



BURGER: FLORA COSTARICENSIS 225 

the Nicaraguan border to San Vito and Agua Buena on the Panama- 
nian frontier. Introduced from Africa or India. This species is appar- 
ently of recent introduction and is spreading rapidly. It is as yet little 
known from the Caribbean slope (Juan Vinas, La Tirimbina). The 
plants form a wiry, tough turf that virtually excludes other species on 
areas such as playing fields, where they are trampled extensively. Not 
previously recorded from the western hemisphere. 

Eragrostis tephrosanthos Schultes, Mant. 2:316. 1824. Eragrostis 
arida Hitchc., J. Wash. Acad. Sci. 23:449. 1933. 

Caespitose annual in small tufts; plants erect, 15-90 cm. tall; culms branched from the 
base or lower nodes; internodes glabrous, hollow; nodes glabrous, dark; leaf sheaths 
glabrous except for a tuft of elongated auricular hairs; ligule a dense row of short white 
hairs, 0.5-0.7 mm. long; leaf blades flat or involute, 3-21 cm. long, 1-5 mm. wide, gla- 
brous. Inflorescences solitary, terminal on the main culm or leafy branches; panicle open, 
pyramidal, 4-25 cm. long, 2-18 cm. wide, about twice as long as wide; branches mostly 
solitary or paired, strongly divergent from the rachis, the largest ones secondarily 
branched; pulvini and branch axils with tufts of elongated hairs; pedicels strongly diver- 
gent from the branches, stiff and flexuous, often longer than the spikelets. Spikelets 
linear-ovate, 4-10.5 mm. long, 1.2-1.5 mm. wide, with 7-20 florets; disarticulation se- 
quential from the base upward, the glumes dropping first, followed by the lemmas, the 
paleas remaining on the intact rachilla; glumes 1-nerved, scabrous on the keel, the first 
0.5-1.4 mm. long, narrowly ovate, acute, the second 0.9-1.7 mm. long, ovate, acute; 
lower lemmas 1.1-2.1 mm. long, ovate, acute, the nerves evident; keel scabrid; surface 
slightly scabrid near the tip; paleas at least three-fourths as long as their lemmas; 
anthers 3, purplish, 0.2-0.3 mm. long; caryopsis elliptic-oblong, 0.6-0.7 mm. long, more 
than half as wide, reddish brown, minutely striate. 

Occasional; fields, roadsides, railroad embankments; elevations from 
sea level to 600 m. Southern General Valley; Piedras Blancas; San 
Jose; La Garita; Turrialba. March to October. Florida and southwest- 
ern United States to Panama; West Indies; in South America to Brazil. 

This species is very similar to E. pectinacea in most respects, dif- 
fering chiefly in the spreading pedicels of the spikelets. Koch states 
that he has not observed hybrids between the two. Some immature 
specimens are difficult to identify definitely. 

Eragrostis viscosa (Retz.) Trin., Mem. Acad. Imp. Sci. St. 
Petersbourg Hist. Acad. 1:397. 1830. Poa viscosa Retz., Obs. Bot. 
4:20. 1786. 

Caespitose annual; culms numerous, ascending to erect, branching from the lower and 
middle nodes, 20-50 cm. tall; internodes less than 1 mm. thick, hollow, thick-walled, 
glabrous; nodes glabrous; prophylla 2.0-2.5 cm. long; sheaths more or less keeled above, 
shorter than the internodes, more or less viscid, the overlapping margins and auricles 
papillose-pilose with hairs up to 4 mm. long; ligule a dense row of stiff hairs, ca. 0.5 mm. 
long; leaf blades 5-13 cm. long, up to 4 mm. wide, bearing scattered weak papillose-based 



226 FIELDIANA: BOTANY 

hairs on the upper surface; stems and leaves often viscid and coated with adherent soil 
particles. Inflorescence terminal on the main culm or on leafy branches; panicle open 
cylindrical, 11-13 cm. long, ca. 2 cm. wide; lower panicle branches solitary and remote, 
the upper more or less whorled; axils lacking tufts of elongated hairs; spikelets rather 
densely arranged on the short lateral branches, the pedicels of lateral spikelets shorter 
than the spikelets. Spikelets ovate, 3.0-5.5 mm. long, disarticulating above the glumes 
and between the florets; first glume ovate, acute, 0.8-1.4 mm. long, 1-nerved; second 
glume similar, 1.0-1.5 mm. long; florets 6-12; lower lemmas 1.1-1.8 mm. long, ovate, 
rather blunt, the lateral nerves submarginal, the internerves scabrid; palea about equal 
to the lemma, the keels ciliate with divergent papillose-based hairs to 0.6 mm. long; 
anthers 3, purple, 0.2-0.3 mm. long. Caryopsis elliptical, 2:1, ca. 0.5 mm. long, reddish 
brown. 

Bluffs, Playas del Coco; disturbed pasture 20 km. N of Liberia on the 
CIA. August to November. Southern Baja California to the Yucatan 
and southward to Panama. Introduced from southeastern Asia. 

Eragrostis ekmanii Hitchc., Man. Gr. W. Ind. 43. 1936. 

A specimen of this species in US bears a label indicating that it was 
collected in Costa Rica (0. Jimenez 713, San Francisco de Guadalupe, 
Jan. 1913). The identification is correct, but the geographic data is 
extremely suspect. The type, which is the only other specimen known, 
was collected on the Isle of Pines, Cuba. 



EREMOCHLOA Biise 

Stoloniferous and rhizomatous perennial; inflorescences are slender terminal or axil- 
lary dorsiventral rames, the sessile awnless fertile spikelets all on one side of the rachis, 
each overlapping the base of the one above, each accompanied by a flattened leathery 
pedicel, bearing at its apex a minute rudimentary spikelet. First glume of sessile 
spikelet oblong, barbed along the lower margins, dorsally flattened, many-nerved, 
bearing a papery apical wing, notched at the midrib, and two narrow flanges on the inner 
side which clasp the margins of the slightly keeled dorsally flattened second glume; 
florets 2, the lower staminate, with membranaceous nerveless lemma and palea, the 
upper similar but perfect-flowered; lodicules 2, fleshy, forked at the apex. 

A small genus of ca. 10 species, native from eastern Asia to Au- 
stralia. The following species is sometimes cultivated in warm cli- 
mates. (Panicoideae: Andropogoneae.) 

Eremochloa ophiuroides (Munro) Hack., in DC., Monogr. Phan. 
6:261. 1889. Ischaemum ophiuroides Munro, Proc. Amer. Acad. Arts 
4:363. 1860. Sehima ciliare (L.) G. Rob., subvar. ophiuroides (Munro) 
G. Rob., Monogr. Androp. 318. 1960. Figure 78. 

Plants extensively stoloniferous, the stolons with short internodes and numerous 
short erect flowering branches; rhizomes also produced; erect flowering culms 10-20 cm. 




FIG. 78. Eremochloa ophiuroides. A, blooming plant; B, rame; C, a sessile spikelet; D, 
portion of a rame, showing two flattened pedicels with rudimentary spikelets at their 
tips. 



227 



228 FIELDIANA: BOTANY 

tall, ca. 1 mm. thick, hollow, glabrous; nodes dark, with a short ciliate fringe at the base; 
leaves 2-3 per culm, the uppermost with a short or rudimentary blade; sheaths mostly 
overlapping, strongly keeled; ligule a short ciliate membrane, 0.5-1.0 mm. long; blades 
short, linear, 3-5 (8) cm. long, abruptly rounded to a scabrid tip, contracted into a short 
pseudopetiole at the rounded, ciliate base. Peduncles slender, 1-5 cm. long, terminal and 
axillary. Inflorescence a stiff slender rame, 3-5 cm. long, ca. 2 mm. thick, the overlapping 
first glumes of the fertile spikelets all on one side of the rachis, the rachis joints and 
pedicels of the abortive pedicellate spikelets on the other. Rachis flattened, tough, 
scarcely disarticulating. Spikelets paired, the sessile ones 3.2-4.0 mm. long, 1.5-2.0 mm. 
wide, often purplish near the apex; second glume equal in length to the first, but nar- 
rower, elliptical, acute, not winged, 3-nerved; florets 2, the lower staminate, the upper 
perfect-flowered; lemma of lower floret 2.5-3.0 mm. long, ovate, acute, nerveless; palea 
about equal; upper lemma 2.5-2.8 mm. long, similar to the first, its palea about equal to 
the lemma; anthers 3, 1.7-2.0 mm. long, purple. Chromosome number n = 9. 

This Asiatic species is often cultivated as a lawn grass in warm moist 
climates and is fairly common in the southeastern United States. Our 
only collection from Costa Rica is from Finca Las Cruces near San Vito 
de Java, where it makes up a lawn. It makes a strong, erosion- 
resisting turf, but the numerous, wiry inflorescences may be objec- 
tionable. It also occurs at El Zamarano, Honduras. Blooming time in 
Central America is in June and July. 



ERIOCHLOA Humboldt, Bonpland & Kunth 

Annual or perennial caespitose or stoloniferous grasses; inflorescence of 1-many 
spikelike racemes borne on a common rachis; spikelets solitary or paired, subsessile or 
short-pedicellate, borne along the lower side of the rachis. Spikelets disarticulating 
below the glumes, dorsally compressed, ovate, acute; the thickened basal rachilla joint 
and first glume united to form a protruding knoblike structure at the base of the spikelet; 
first glume abortive or reduced to a minute cufflike scale embracing the rachilla joint; 
second glume and sterile lemma subequal, completely covering and concealing the 
shorter fertile floret; fertile lemma cartilaginous, minutely rugose-striate, the margins 
not inrolled, covering the edges of the flat palea of similar texture; tip of the lemma 
minutely bristly or prolonged into a minute awn. 

About 25 species in warm climates of both eastern and western 
hemispheres. (Panicoideae: Paniceae.) 

KEY TO SPECIES OF Eriochloa 

la. Inflorescence of 1-3 simple racemes, each 1-2 cm. long E. distachya 

Ib. Inflorescence of numerous usually branched primary branches, the longer ones 5-8 
cm. long E. polystachya 

Eriochloa distachya H.B.K., Nov. Gen. & Sp. 1:95, Tab. 30. 1816. 
Helopus brachystachys Trin., Sp. Gram. Icon. & Descr. II, Tab. 277. 
1829. Figure 79. 




FIG. 79. Eriochloa species. E. polystachya: A, panicle; B, two views of a spikelet; C, 
fertile floret; E. distachya: D, inflorescences; E, spikelet; F, fertile floret. 



229 



230 FIELDIANA: BOTANY 

Caespitose annual; plants 25-50 cm. tall, erect, or the culm bases decumbent; branch- 
ing freely from the base and the culm nodes; prophylla 2-3 cm. long; culms 1 mm. thick, 
hollow, glabrous; nodes bearded with ascending or retrorse hairs; leaf sheaths glabrous 
or villous on the back and margins; ligule a minute fringe of white hairs, 0.4-0.5 mm. 
long; leaf blades flat, 2-13 cm. long, 2-6 mm. wide, mostly glabrous, the uppermost 
sometimes reduced. Peduncle slender, 5-12 cm. long, glabrous near the base, increas- 
ingly villous toward the apex; inflorescence of 1-2 silky racemes, these 1-2 cm. long, 
usually arched, 1-sided, the spikelets alternating in 2 rows along the lower side of the 
densely silky-villous rachis; pedicels minute, villous, with a ring of longer hairs near 
their apex; spikelets placed with the sterile lemma facing toward the midline of the 
rachis and the backs of fertile lemmas facing outward. Spikelets elliptic-ovate, 2.5-3.5 
mm. long, acute, dorsally compressed, with a protruding basal knob ca. 0.3 mm. long and 
0.5 mm. wide formed of the thickened basal rachilla joint surrounded by an abortive 
cuplike first glume; surface of disarticulation umbrella-shaped, smooth and shiny; second 
glume and sterile lemma equal, similar, 2.3-3. 1 mm. long, completely covering the fertile 
floret; the glume 5-nerved, the lemma 3-nerved, both bearing stiff erect to spreading 
hairs, those toward the apex much longer than the rest; fertile lemma stiff, minutely 
rugulose, elliptical, 1.9-2.3 mm. long, faintly 3-nerved, bearing a few minute spicules at 
the tip, the flat margins barely covering the edges of a flat palea of similar texture; 
anthers 3, tan, 1.2-1.5 mm. long; caryopsis elliptic-oblong, 1.5 mm. long, white, opaque. 
Chromosome number n = 9 from a Costa Rican specimen. 

Rare; savannas of Boruca and Buenos Aires. December. Guatemala 
and Costa Rica to Panama, Brazil and Paraguay. 

Eriochloa polystachya H.B.K., Nov. Gen. & Sp. 1:95. Tab. 31. 
1816. Figure 79. 

Duration indefinite but probably perennial; culm bases long-decumbent and rooting at 
the nodes; upper parts of culms ascending, 1-2 m. long, branching freely, glabrous, 
hollow, thin-walled, 3-4 mm. thick; nodes conspicuously bearded with spreading or re- 
trorse hairs; sheaths more or less papillose-hispid; ligule a minute stiff membrane, 
crowned with a longer dense row of silky white hairs, totaling 0.8-1.2 mm. long; collar of 
the sheath and base of the upper blade surface minutely velvety; blades glabrous or 
sparsely papillose-hairy, 10-25 cm. long, 8-15 mm. wide. Peduncles exserted up to 12 
cm., glabrous except for the heavily bearded apex; inflorescences terminal on leafy 
culms; panicles narrowly ellipsoidal, 15-25 cm. long, 2-3 x longer than wide; rachis and 
branches more or less papillose-hirsute; branches straight, ascending, usually re- 
branched, the spikelets racemose, solitary or paired along the undersides of the primary 
or secondary branches; members of a pair unequally short-pedicellate; backs of the 
fertile lemmas placed away from the rachis. Spikelets narrowly ovate, 2.5:1, acute, 
3.2-3.6 mm. long with a small protruding basal knob; first glume 0.2 mm. long, truncate, 
cufflike, usually purple; second glume and sterile lemma equal, sparsely appressed- 
hairy, 3.0-3.5 mm. long, ovate, acute; the second glume 5-nerved; sterile lemma with 3 
strong nerves and 2 weak marginal ones; fertile floret 2.2-2.5 mm. long, noticeably 
shorter than the glume and sterile lemma, elliptical, faintly 3-nerved, with a minute 
apical awn ca. 0.1 mm. long; lemma and palea white, stiff, faintly striate, the margins of 
the lemma flat, covering the edges of the palea; anthers 3, greenish, 1.0-1.5 mm. long; 
stigmas purple. Chromosome number n = 18 from Costa Rican specimens. 



BURGER: FLORA COSTARICENSIS 231 

Cultivated as a forage crop and commonly escaped to roadsides and 
margins of ponds; elevations up to 1,200 m.; most common in humid 
areas. March to September. West Indies and northern South America. 
Not previously reported as a wild plant in Central America. Common 
name in Costa Rica is Janeiro. The plants are very similar to 
Brachiaria mutica ("Para grass"). 

ERIOCHRYSIS Beauvois 

REFERENCE: J. R. Swallen, Notes on grasses: Eriochrysis, 
Phytologia 14:88-91. 1966. 

Caespitose erect perennial; inflorescence a dense silky cylindrical intricately branched 
panicle of short rames; spikelets awnless, paired at each node of the rachis, one sessile 
and the other short-pedicellate; disarticulation at the bases of the sessile spikelets, the 2 
spikelets of the pair falling together or the pedicellate one dropping from the pedicel. 
Glumes, rachis internodes, and pedicels all densely brown-silky. Spikelets of each pair 
similar, but the pedicellate one slightly smaller; glumes equal, chartaceous, completely 
covering and concealing the inner spikelet parts; outline of spikelet narrowly ovate, 
acute; first glume flat on the back, with inflexed margins which cover the edges of the 
keeled second glume; callus, margins, and tip of the first glume and the keel and tip of 
the second glume fringed with long, silky, golden-brown hairs. Sterile lemma and fertile 
lemma thin, nerveless, slightly shorter than the glumes; no paleas present; lodicules 
thick and fleshy, truncate. Sessile spikelet with a perfect flower; pedicellate spikelet 
with a pistillate flower only. 

Species about 10, from tropical America, Africa, and Asia. 

Eriochrysis cayanensis Beauv., Ess. Nouv. Agrost. 8. PL 4, f. 11. 
1812. Saccharum cayennense (Beauv.) Benth., J. Linn. Soc. Bot. 
19:66. 1881. S. cayennense Benth., Roberty, Mon. Syst. Androp., 
Boissiera 9:360. 1960. Figure 80. 

Perennial, in small, dense clumps from a deep-seated base; plants 90-300 cm. tall; basal 
leaves numerous, their blades very elongate, up to 50 cm. long and 6 mm. wide, often 
folded; bases of culms clothed with the fibrous remains of the old sheaths; culms erect, 
2-4 mm. thick, hollow, glabrous; nodes densely bearded with straight ascending hairs; 
foliage as a whole copiously velvety-pubescent; sheaths densely hairy on the collar; ligule 
a short ciliate membrane, 1-2 mm. long; blades of culm leaves shorter and wider than the 
basal ones, up to 12 mm. wide; uppermost blade much reduced; inflorescence included at 
the base or the peduncle exserted up to 15 cm. Inflorescence dense, cylindrical, lobulate, 
lustrous golden-brown, the densely clustered spikelets mostly concealed by the long 
silky pubescence of spikelets, rachis internodes and pedicels; length 12-18 cm., width 1-3 
cm.; branches short, ascending, concealed by the spikelets and hairs. Pedicels and rachis 
joints silky-pubescent, very short, 1.0-1.3 mm. long. Spikelets paired, or the terminal 
segment of a rame bearing a sessile spikelet and 2 pedicellate ones. Spikelets 2.0-4.4 
mm. long, the pedicellate member of the pair usually shorter than the sessile one; glumes 




FIG. 80. Eriochrysis cayanensis. Blooming plant. 
232 



BURGER: FLORA COSTARICENSIS 233 

subequal and the full length of the spikelet, concealing the inner parts; lower floret 
sterile, represented by an empty lemma slightly shorter than the first glume; upper 
floret with a keeled lemma ca. as long as the second glume but no palea; flower of sessile 
spikelet perfect, that of the pedicellate spikelet pistillate; lodicules 2, large and fleshy, 
truncate; anthers 3, yellow, 1.3-1.7 mm. long. Chromosome number n = 10 from Costa 
Rican specimens. 

Open marshy places, from near sea level to 1,400 m. July to October. 
Uncommon in Costa Rica; known from General Viejo and Canas Gor- 
das. Mexico to Bolivia and Argentina. 

This is one of the most striking of the tropical American grasses, 
easily recognized by its beautiful brown inflorescence, somewhat re- 
sembling a small cattail. The specific epithet was spelled cayanensis by 
Beauvois in two separate places in his work. Later authors have usu- 
ally spelled it cayennensis, referring to Cayenne. Beauvois, however, 
makes no such reference. 



EUCLASTA Franchet 

Inflorescences terminal on the main culm or on leafy lateral branches. Peduncle very 
slender, flexuous; rames several, slender, borne racemosely along a slender central 
rachis, each rame on a filiform naked flexuous branch. Spikelets dorsally compressed, 
the basal 1-several pairs sterile, the members of the pair alike and awnless; rachis 
between sterile pairs not disarticulating, the sessile spikelets remaining on the rachis 
after the upper parts of the rame have disarticulated; pedicellate spikelets of basal pairs 
disarticulating; upper spikelet pairs of the rame dimorphic, the sessile perfect-flowered 
spikelet bearing an exserted twisted and geniculate awn, the pedicellate one awnless, 
sterile. Disarticulation at the apex of each internode of the rachis, the paired spikelets 
falling together or the pedicellate spikelet deciduous; rachis segments and pedicels flat, 
ciliate, with a very thin, translucent band down the length of the center; terminal rachis 
segment bearing 1 sessile spikelet and 2 pedicellate ones; glumes membranaceous, the 
first flat on the back, many-nerved, ciliate and slightly keeled on the margins of the 
upper half, the lower margins incurved; second glume shorter than the first, boat- 
shaped, 3-nerved; sessile spikelets usually with a thin, nerveless lower lemma lacking 
palea or flower; upper fertile lemma reduced to the flattened whitish base of the awn; 
lodicules 2, truncate; anthers 3, linear. 

The genus Euclasta consists of a single species, distributed in the 
tropics of Africa and America. It is related to Andropogon, Hypar- 
rhenia, and Bothriochloa, being closest to the last in the possession of 
rachis segments and pedicels with thin translucent centers. The per- 
sistent basal portion of the rames, bearing persistent sessile spikelets, 
along with the delicately peduncled rames, are characteristic of 
Euclasta. The spikelets are much softer than is usual in this tribe. 
(Panicoideae: Andropogoneae.) 

Euclasta condylotricha (Hochst.) Stapf, Fl. Trop. Africa 9:181. 



234 FIELDIANA: BOTANY 

1917. Andropogon condylotrichus Hochst. in Steud., Syn. PL Gram. 
377. 1855. Amphilophis piptatherus (Hack.) Nash, N. Amer. Fl. 
17:127. 1912. Figure 81. 

Weak sprawling annual, the decumbent stems rooting at the lower nodes, branching 
freely from the lower nodes; internodes glabrous, pithy; nodes bearded; sheaths longer 
or shorter than the internodes, glabrous except pilose on the collar; ligule a firm brown- 
ish membrane, ca. 1 mm. long, ciliate with white hairs longer than the membranaceous 
part; leaf blades flat, 7-20 cm. long, 3-8 mm. wide, hirsute beneath, usually glabrous 
above, usually with a few long, pustulose-based hairs on the basal margins. Peduncles 
very slender, terminal or axillary from the upper culm nodes, heavily bearded at the 
apex and on the rachis nodes. Rames usually 2-6, solitary or paired at the rachis nodes, 
2-4 cm. long, forming a fan-shaped cluster. Basal spikelet pairs: spikelets about equal, 
4.6-6.0 mm. long, sterile; ovate 3:1, first glume 5-7-nerved, narrowly truncate at the 
apex; second glume shorter, boat-shaped, 3-nerved; basal portions of the glumes bearing 
stiff spreading hairs. Upper spikelet pairs: sessile spikelets 3.5-3.8 mm. long, the first 
glume 5-7-nerved, flat on the back, bristly hirsute on the lower half, slightly truncate at 
the apex; second glume ca. 3.5 mm. long, 3-nerved; sterile lemma thin and nerveless, ca. 
half as long as the spikelet; upper lemma reduced to the brown, twisted and geniculate 
awn, 3-4 cm. long; anthers 1.0-1.2 mm. long. Chromosome number n = 10 from a 
Venezuelan specimen. 

Tuff outcrops in savanna and rocky sea cliffs, sea level to 300 m., 
Hacienda Murcielago. October to December. Mexico to Venezuela and 
Brazil; West Indies; tropical Africa. 

EUSTACHYS Desvaux 

REFERENCE: G. V. Nash, A revision of the genera Chloris and Eus- 
tachys in North America, Bull. Torrey Bot. Club 25:432-450. 1898. 

Caespitose perennial grasses, often with short stolons; foliage glabrous; leaves mostly 
aggregated near the bases of the culms, the sheaths strongly keeled; culms hollow; 
inflorescence solitary, terminal, of several whorled ascending spikes; spikelets densely 
arranged on the lower sides of a slender triquetrous rachis, alternating in 2 rows but 
forming a single file, oriented at right angles to the rachis. Spikelets strongly laterally 
compressed, the glumes and lemmas keeled; first glume narrow, acuminate, 1-nerved; 
second glume oblong, flattened on the back, markedly bifid at the apex, the single nerve 
protruding as a short awn; fertile lemma broad, blunt, awnless or nearly so, dark brown 
and shining, with a short truncate callus; nerves 3, the lateral marginal; palea equalling 
the lemma; rachilla inflated, bearing a club-shaped truncate rudimentary lemma. 

This small genus of ca. 10 species of warm climates of the western 
hemisphere is closely related to Chloris, with which it is often united. 
It differs in the broad, dark brown, awnless florets, in the placement of 
the spikelets perpendicular to the rachis rather than appressed to it, in 
the single file, the oblong, bifid second glume, and the hollow culms. 
(Chloridoideae: Chlorideae.) 




FIG. 81. Euxlasta condylotricha. A, inflorescence; B, old inflorescence with persistent 
sessile spikelets; C, rame with awnless basal spikelets and awned upper sessile 
spikelets. 



236 FIELDIANA: BOTANY 

Eustachys petraea (Swartz) Desv., Nouv. Bull. Sci. Soc. Philom. 
Paris 2:189. 1810. Chloris petraea Swartz, Prodr. Veg. Ind. Occ. 25. 
1788. Figure 82. 

Perennial, in clumps, the bases with short stout stolons; plants 30-100 cm. tall, erect; 
culms compressed, glabrous, 2-3 mm. thick, hollow, thick-walled; nodes glabrous; leaves 
mostly clustered near the bases of the culms, the basal sheaths much overlapping, 
strongly keeled; foliage glaucous; ligule a minute strongly ciliate membrane, ca. 0.2 mm. 
long; blades 6-15 cm. long, 4-7 mm. wide, flat or folded, glabrous, scabrous on margins 
and midrib, strongly keeled beneath, the uppermost much reduced; tip blunt and apicu- 
late. Inflorescence solitary, terminal, vase-shaped, of 3-8 slender spikes, each 4-9 cm. 
long, the spikelets attached in 2 rows along the lower sides of a slender triquetrous 
rachis, crowded, placed approximately perpendicular to the rachis; adjacent spikelets 
intercalated with each other, thus forming a single file. Spikelets 1.6-2.0 mm. long, 
disarticulating above the persistent glumes; first glume 0.9-1.3 mm. long, 1-nerved, 
lanceolate, the scabrous keel curved; second glume 1.1-1.5 mm. long, oblong, strongly 
lobed at the tip, the back rather flat, short-awned from between the lobes; awn 0.3-0.5 
mm. long; fertile floret 1.6-2.0 mm. long, the lemma rotund, strongly laterally com- 
pressed, dark brown and shining, awnless or minutely apiculate, short-ciliate on the 
blunt callus, the keel, and the marginal nerves; palea as long as the lemma, obovate, 
brown and shining, flat; anthers 3, ca. 0.6 mm. long, yellow; rudimentary floret reaching 
the tip of the fertile lemma, consisting of a club-shaped, truncate, hollow empty lemma, 
contracted at the base into a thick, fleshy whitish rachilla. Chromosome number n = 20 
from Costa Rican material. 

Sandy beach of the Caribbean Sea, Limon Airport to Boca Banano; 
Estero Negro; Playa Westfalia. Blooming yearlong. Southeastern 
United States to Texas and eastern Mexico, Belize, Honduras, Costa 
Rica and Panama; West Indies. The sporadic occurrence of this species 
near Caribbean ports in Central America suggests that it may have 
been introduced. It has grown at Limon at least since 1895. 

FESTUCA Linnaeus 

Perennial grasses; inflorescence a terminal panicle; spikelets several-many-flowered, 
laterally compressed, disarticulating above the glumes and between the florets; lemmas 
with a hard callus, slender, usually 5-nerved, tapering to an acuminate apex or an awn; 
palea mostly as long as the lemma; anthers 3; flowers chasmogamous. 

A large genus of perennial grasses of cold and temperate climates, in 
the tropics restricted to upper elevations. The genus is often united 
with Vulpia, which differs in containing annual species with one anther 
and cleistogamous flowers. A few instances of intergeneric hybridiza- 
tion between Festuca and Vulpia are known. Species of Festuca may 
be confused with certain species of Bromus. The latter genus, how- 
ever, has leaf sheaths with united edges and lemmas with apical teeth, 
the awn arising between them. (Pooideae: Poeae.) 




FIG. 82. Eustachya petraea. A, stolon with a cluster of keeled basal leaf sheaths; B, 
inflorescence; C, portion of a spike; D, a spikelet. 



237 



238 FIELDIANA: BOTANY 

KEY TO SPECIES OF Festuca 

la. Leaf blades flat, 3-12 mm. wide 2 

Ib. Leaf blades involute or less than 3 mm. wide 5 

2a. Lemmas awnless or with awn less than 4 mm. long 3 

2b. Lemmas long-awned, awn 10-15 mm. long F. breviglumis 

3a. Bases of leaf blades wider than sheath, auricled; florets 3-10 F. arundinacea 

3b. Bases of leaf blades as wide as sheath, lacking auricles; florets 3-5; native species of 

forests and alpine sites 4 

4a. Lemmas awnless, lowermost 5.5-7.0 mm. long; anthers 2.0-2.8 mm. long, pur- 
ple; lower panicle branches in 5's; spikelets very numerous . . F. amplissima 
4b. Lemmas short-awned, lowermost 9-11 mm. long; anthers 3-4 mm. long, yellow; 
lower panicle branches paired; spikelets few F. chiriquensis 

5a. Lemmas less than 3.5 mm. long, awnless; plants 10-25 cm. tall; leaf blades thread- 
like F. tenuifolia 

5b. Lemmas 5-8 mm. long, usually awned; plants 15-110 cm. tall 6 

6a. Ligule minute; introduced grasses in upper elevation pastures of volcanoes 7 
6b. Ligule 1.0-2.5 mm. long; native grasses of paramos above 3,000 m. elevation 8 

7a. Clumps dense, basal leafy shoots (innovations) arising within the basal sheaths; 
lower sheaths stramineous, persistent F. ovina 

7b. Clumps loose, sprawling, basal leafy shoots bursting through basal sheaths near 

their bases; lower sheaths reddish, breaking down into fibers F. rubra 

8a. Basal leaf blades less than 2.0 mm. wide, with 3-4 coarse ridges on upper 

surface F. toliicensis 

8b. Basal leaf blades 2-4 mm. wide, with 6-12 ridges on upper surface 

F. dolichophylla 

Festuca amplissima Rupr. ex Fourn., Mex. PL 2:125. 1881. Figure 
85. 

Tall, stout perennial; plants 110-150 cm. tall; culms erect from hard bases; basal leaves 
numerous, their sheaths breaking down into stiff fibers; culms unbranched, stiff, 2-3 mm. 
thick, hollow, glabrous or scabrous; nodes dark, contracted, glabrous; sheaths nearly as 
long as the internodes, faintly scabrous; ligules membranaceous, 0.5-1.8 mm. long, the 
basal ones very short; blades 20-50 cm. long, 7-8 mm. wide, stiff and erect, scabrous 
beneath, tapering into a long involute tip. Peduncle scabrid, exserted up to 40 cm.; 
panicle solitary, terminal, up to 30 cm. long, narrowly elliptical; branches up to 5 per 
node, usually 10-12 cm. long, ascending, naked for several centimeters near the base; 
rachis, branches, and pedicels angular, scabrous on the edges; spikelets appressed along 
the branches, their pedicels mostly short. Spikelets laterally compressed, ca. 10 mm. 
long; first glume 3.0-4.5 mm. long, linear, 1-nerved; second glume 4.8-6.0 mm. long, 
3-nerved, lanceolate; florets 3-5, often with a small terminal rudiment; lemmas lanceo- 
late, scabrid, evidently 5-nerved, keeled, awnless, acuminate, often purplish on the 
back, bronzy near the tip, 5.5-7.0 mm. long; palea nearly as long as its lemma, tapering 
abruptly to a point, scabrid between the keels; rachilla slender, scabrous; anthers 3, 
purple, 2.0-2.8 mm. long. 

Rare; known from the devastated area at the head of the Rio Reven- 
tado on Irazu, and from the upper canyon of the Rio Talari on Chirripo 
Grande, at the margin of the paramo; elevations 2,700-3,250 m. 



BURGER: FLORA COSTARICENSIS 239 

January to April; November. Southern Mexico; Guatemala; Costa 
Rica; Volcan Chiriqui in Panama. Our specimens have somewhat 
smaller spikelets and longer ligules than the Pringle specimens 3945 
and 9555 cited by Piper in N. Am. Sp. Festuca, from Mexico, but are 
generally similar. 

Festuca arundinacea Schreb., Spic. Fl. Lips. 57. 1771. Figure 83. 

Perennial, forming large clumps; plants to 150 cm. tall; culms erect to spreading, 
unbranched, to 5 mm. thick, glabrous; nodes dark, glabrous, shrunken; sheaths elon- 
gate, striate; ligules membranaceous, up to 2 mm. long; leaf blades 2-5 per culm, 10-60 
cm. long, 3-12 mm. wide, glabrous, coarse and tough, flat, strongly ridged above, the 
upper surface and margins scabrous, base auricled; basal blades numerous, lying flat on 
the ground in cropped or grazed plants. Peduncle exserted 10-50 cm.; inflorescence a 
solitary terminal panicle, erect or nodding, rather narrow and dense; rachis and 
branches angled and scabrous; spikelets rather densely clustered along the branches, 
short-pedicellate. Spikelets 10-18 mm. long, the florets crowded because of the short 
rachilla segments; first glume 3-6 mm. long, 1-nerved, lanceolate; second glume 4.5-7.0 
mm. long, 3-nerved, lanceolate-ovate; florets 3-10; lemmas 6-9 mm. long, glabrous, 
lanceolate-oblong, 5-nerved, tapering to an acuminate apex of a short awn 1-3 mm. long; 
palea ca. as long as the lemma, the keels scabrous, rachilla segments ca. 1 mm. long, 
upwardly scabrous; anthers 3, purple, 3.5-4.0 mm. long. Chromosome number n = 21. 

Moist pastures, Irazii and Turrialba, 1,800-2,800 m. elevation. Au- 
gust to November, probably yearlong. Introduced from Europe as a 
pasture grass; naturalized in various parts of North America. This 
species was apparently reported as F. elatior L. in the Grasses of 
Central America. 

Festuca breviglumis Swallen, Contr. U.S. Natl. Herb. 29:398. 
1950. Figure 84. 

Perennial; culms erect or the bases decumbent; plants to 130 cm. tall; culms un- 
branched, 3 mm. thick, glabrous, hollow; nodes dark, shrunken, glabrous; culm leaves 
ca. 4, their sheaths very elongate, up to 25 cm. long, glabrous; ligules 0.5-0.8 mm. long, 
membranaceous, minutely ciliolate; blades flat or folded, up to 35 cm. long, 5-7 mm. 
wide, glabrous, the upper surface finely nerved; lower surface scaberulous. Panicle 
solitary, terminal, up to 27 cm. long, 15 cm. wide, open, nodding; branches paired, the 
longest 18 cm. long; rachis and branches scabrous, the lower third to half of the branch 
devoid of spikelets. Spikelets few, 15-20 mm. long without the awns; first glume 3-5 mm. 
long, 1-nerved, acicular; second glume 6.5-8.5 mm. long, narrowly lanceolate, 3-nerved; 
florets 4-5; lemmas narrowly lanceolate, rounded on the back, the upper portion folded 
and keeled, evidently 5-nerved, but with an extra pair of weak marginal nerves near the 
base, scabrid on the back, tapering to an awn up to 15 mm. long; lowermost lemma 
14.0-15.5 mm. long, the upper ones shorter; palea narrowly elliptical, tapering to a 
narrow tip, scabrous on the nerves, two-thirds to three-fourths as long as the lemma; 
rachilla scabrous, the ultimate segment sterile or bearing a long-awned rudiment at its 
tip; anthers 3, purple, 4.0-4.5 mm. long. 

Rare; known in Costa Rica only from the type from Copey, and from 




FIG. 83. Festuca species. F. arundinacea: A, portion of panicle and ridged upper 
surface of leaf blade; F. tenuifolia: B, panicle and threadlike leaf blades; F. ovina: C, 
portion of panicle; D, leafy shoot with intravaginal branching; F. rubra: E, panicle; F, 
base of plant with extravaginal branching. 



240 




FIG. 84. Festuca species. F. breviglumis: A, panicle; B, culm base; C, spikelet; F. 
chiriquensis: D, spikelet. 



241 



242 FIELDIANA: BOTANY 

a recent specimen collected along the Carretera Interamericana north 
of San Cristobal Norte; elevations 2,000-2,200 m. September to De- 
cember. Also known from Guatemala. 

Festuca chiriquensis Swallen, Ann. Missouri Bot. Gard. 30:116. 
1943. Figure 84. 

Perennial, in small clumps from a deep-seated base; plants 80-130 cm. tall; culms un- 
branched, 2-3 mm. thick, glabrous, hollow; culm leaves ca. 4; sheaths glabrous, much 
shorter than the internodes, scabrid; ligule a minutely ciliolate membrane, 0.7-2.0 mm. 
long; blades soft, flat, dark green and shining, slightly scabrid, 15-50 cm. long, 4-7 mm. 
wide. Peduncle exserted to 15 cm.; inflorescence a solitary terminal panicle, open, nod- 
ding, few-flowered, 15-30 cm. long; branches few, paired, the longest 15 cm. long, the 
spikelets borne on the outer third. Spikelets 3-4-flowered, 15-17 mm. long; first glume 
subulate, 1-nerved, 5.5-6.7 mm. long; second glume linear-lanceolate, 3-nerved, scab- 
rous on the keel, 8.0-9.5 mm. long; lowermost lemma 9-11 mm. long, lanceolate, con- 
spicuously 5-nerved, scabrous, minutely toothed at the apex; awn stiff, scabrous, 1-4 
mm. long; palea equal to the lemma, scabrous on the keels, nerves prolonged into awns 
up to 1 mm. long; rachilla scabrous; anthers 3, yellow, 3.0-3.9 mm. long. 

Moist oak forests, Chirripo Grande, 3,000-3,200 m. elevation. The 
type was from Volcan Chiriqui in Panama. September to April. This 
rare species was previously known only from the type. It is very 
similar to F. breviglumis, from which it differs in having much longer 
glumes, shorter lemmas, longer paleas which are awned, and smaller 
yellow anthers. 

Festuca dolichophylla Presl, Rel. Haenk. 1:258. 1830. Figure 85. 

Perennial, in large, dense clumps; plants erect, 65-110 cm. tall; culms unbranched, 
hollow, glabrous, 2-4 mm. thick; internodes very elongated; nodes dark, shrunken, 
glabrous; sheaths glabrous, about as long as the internodes; ligules membranaceous, 
1.0-2.5 mm. long; leaves mostly basal; blades elongate, up to 50 cm. long, erect, involute, 
glabrous or scabrous beneath, puberulent or glabrous above, 2-5 mm. wide, upper sur- 
face with 6-12 strong ridges. Peduncle glabrous or slightly scaberulous, up to 15 cm. 
long; panicle terminal, solitary, narrowly elliptical, nodding, 10-25 cm. long, 3-4 cm. 
wide; lower branches usually paired, up to 12 cm. long, ascending; spikelets appressed 
along the branches. Spikelets 10-17 mm. long, usually purple, with 5-7 florets; first 
glume linear-triangular, 1-nerved, 4-6 mm. long; second glume linear-lanceolate, 3- 
nerved, 6.0-7.2 mm. long; lemmas obscurely 5-nerved, narrowly lanceolate, more or less 
scaberulous, 6.5-8.0 mm. long, rounded on the back, the margins infolded; apex acumi- 
nate or short-awned, the awn less than 1 mm. long; palea nearly as long as the lemma, 
narrowed to the tip, scabrous on the keels; rachilla segments slender, scabrous, the 
terminal one half as long as the floret below, naked or bearing an abortive floret at its tip. 
Chromosome number n = 21 from Costa Rican material. 

Volcanic cinders and mud about the craters of Irazu and Turrialba, 
Chirripo Grande; elevations 3,100-3,400 m. June to August. Costa 
Rica; Volcan Chiriqui in Panama; to Chile. 

This species is similar to F. amplissima, but differs in the stiff, 




FIG. 85. Festuca species. F. dolichophylla: A, panicle and leaf blades; B, spikelet; F. 
amplissima: C, panicle; D, leaf sheath and blade; E, spikelet. 



243 



244 FIELDIANA: BOTANY 

involute narrow leaves, paired panicle branches, larger spikelets with 
more florets. It also resembles F. tolucensis of Mexico, but differs in 
the much coarser foliage. 

Festuca ovina L., Sp. PI. 73. 1753. Figure 83. 

Densely caespitose perennial; intravaginal innovations numerous, most of the foliage 
borne near the base of the plants; culms 15-60 cm. tall; leaf blades of innovations and 
culms stiff, folded; foliage glabrous. Inflorescence a solitary terminal panicle, usually 
5-10 cm. long, with few ascending branches, the spikelets clustered near the tips. 
Spikelets with 3-9 florets; lemmas short-awned, rounded on the back, stiff. 

This is a widespread and extremely polymorphous European 
species, not previously reported from Central America and known only 
from the following Costa Rican specimen. A number of European pas- 
ture grasses occur in these alpine pastures, and were evidently intro- 
duced long ago in pasture seed mixtures. Cartago, in pasture, upper 
slopes of Volcan Irazii, Godfrey 66649, 24 February 1965. 

Festuca rubra L., Sp. PI. 74. 1753. Figure 83. 

Perennial, in loose, sprawling tufts; plants 15-90 cm. tall; the bases of the culms often 
decumbent or creeping; foliage mostly basal, the innovations extravaginal; culms ca. 1 
mm. thick, hollow, ridged, glabrous; old basal sheaths becoming dark reddish, eventu- 
ally breaking down into loose fibers; ligule a minute membrane; blades 3-40 cm. long, 
mostly folded, appearing 0.5-1.0 mm. wide as folded, as much as 2 mm. wide when flat. 
Peduncle elongate, as much as half the height of the plant; panicle solitary, terminal, 
3-17 cm. long, slender, erect or nodding; branches solitary or paired, the longest up to 6 
cm. long, angled and scabrous, few-flowered; spikelets overlapping. Spikelets 5-14 mm. 
long, with 3-9 florets; first glume 2.0-3.5 mm. long, 1-nerved, narrowly lanceolate; sec- 
ond glume 3.5-5.0 mm. long, 3-nerved, lanceolate; lemmas 5-6 mm. long, lanceolate, 
5-nerved, glabrous or scabrid toward the tip, tapering into a stiff awn 1-3 mm. long; 
palea equal to the lemma, scabrid on the keels; anthers 3, 2-3 mm. long, purple. 

Pastures and clearings, upper slopes of Volcan Barba and Volcan 
Turrialba; elevations 2,400-2,800 m., rare. June to August. This 
species is widespread in cooler regions of the northern hemisphere and 
is extensively cultivated as a lawn grass. In Central America, it is 
known only from Costa Rica. Our collections are undoubtedly survivals 
from pasture seed mixtures imported from Europe, since they grow in 
areas harboring numerous European plants. 

Festuca tenuifolia Sibth., Fl. Oxon. 44. 1794. F. capillata Lam., 
Fl. Franc. 3:597. 1778. Figure 83. 

Perennial, in dense clumps with numerous erect basal blades; plants 10-25 cm. tall; 
culms thin, hollow, glabrous or scaberulous; leaf blades hairlike, rolled, less than 0.5 
mm. thick; ligule a minute membrane; sheaths with small auricles; peduncle slender, half 
the height of the plant. Inflorescence a solitary terminal panicle, 2-10 cm. long, linear, 



BURGER: FLORA COSTARICENSIS 245 

with short, erect, few-flowered scabrous branches. Spikelets 3-7 mm. long, 3-8-flowered; 
first glume 1-nerved, lanceolate, 1.5-2.5 mm. long; second glume 3-nerved, ovate, 2.5-3.5 
mm. long; lemmas 2.5-3.5 mm. long, ovate, acuminate, awnless, 5-nerved, glabrous or 
scabrid near the tip; palea as long as the lemma; anthers 3, 1-2 mm. long, yellow or 
purple. 

Moist pasture, south slope of Volcan Turrialba, elevation 3,000 m. 
August. This species is European and has been introduced sparingly in 
the northern United States. The collection indicated above is appar- 
ently the first from Central America. The plants occurred in an area 
where numerous grasses of European origin grow. Probably, this 
species was introduced in pasture seed mixtures. 

Festuca tolucensis H.B.K., Nov. Gen. & Sp. 1:153. 1816. 

Caespitose perennial in dense tufts; culms erect, up to 100 cm. tall; unbranched; 
foliage mostly aggregated near the base of the plants; internodes glabrous, 1.5-2.0 mm. 
thick; nodes dark, contracted; leaf sheaths glabrous, granular-roughened; ligule a thin 
membrane, 1.0-2.5 mm. long; basal leaf blades up to 25 cm. long, scabrous, involute, 
1.0-1.5 mm. wide, the upper surface 3-4-ridged, scaberulous; basal foliage reaching 
one-half to two-thirds the height of the plants, the upper portions of the culms nearly 
leafless. Peduncles exserted up to 30 cm.; inflorescences solitary, terminal; panicles 
11-20 cm. long, open but narrow, few-flowered; branches paired or solitary. Spikelets 
usually purplish, 9-14 mm. long; 6-8-flowered; first glume 4.5-6.3 mm. long, narrowly 
triangular, 1-nerved; second glume 6.0-7.4 mm. long, ovate, acute, 3-nerved; lemmas 
narrowly ovate, acuminate or awn-tipped, 6-8 mm. long, scaberulous; palea slightly 
shorter, bifid at the tip; anthers 3, yellow, 2.8-3.4 mm. long. 

Rare; summit of Irazu; Valle de los Conejos, Chirripo. Apparently 
blooming yearlong. Southern Mexico (Toluca); Guatemala; Costa Rica. 

This species is difficult to distinguish with certainty from F. 
dolichophylla. The very slender, elongate, scabrous basal foliage 
blades are the best character, but some individuals are intermediate. 
The chromosome number of n = 21 has been previously reported and is 
the same as that of Costa Rican F. dolichophylla. The spikelets of our 
material are a good match for type fragments of F. tolucensis in US. 



GLYCERIA R. Brown 

Perennial aquatic or paludose grasses; sheaths with united edges; inflorescence a 
panicle; spikelets several-many-flowered, terete or compressed, disarticulating very 
readily above the glumes and between the florets; glumes usually 1-nerved, blunt; lem- 
mas 5-9-nerved, the nerves conspicuous, not converging but running parallel from base 
to the usually blunt apex. (Pooideae: Meliceae.) 

Glyceria plicata (Fries) Fries, Nov. Fl. Suec. Mant. 111:176. 1842. 
G. fluitans var. plicata Fries, Nov. Mant. 11:6. 1839. Figure 86. 




FIG. 86. Glycerin plicata. A, spikelet; B, lemma; C, panicle. 



246 



BURGER: FLORA COSTARICENSIS 247 

Culms 30-75 cm. long, the basal portion creeping and much-branched, the upper part 
ascending, not branched, glabrous, rather succulent, hollow; sheaths mostly overlap- 
ping, slightly roughened; ligules brownish, membranaceous, 2-8 mm. long, decurrent on 
the sheath margins; blades 5-30 cm. long, 3-14 mm. wide, flat or folded, scabrid beneath, 
tapering abruptly to an acute apex. Peduncle mostly included, smooth; inflorescence 
solitary, terminal, 20-25 cm. long, cylindrical, strict when young but the branches 
spreading in fruit; branches whorled, with up to 7-8 spikelets; pedicels 1.0-7.5 mm. long; 
spikelets mostly appressed to the branchlets, nearly terete, 10-25 mm. long; florets 7-15; 
first glume 1.5-2.5 mm. long, 1-nerved; second glume 2.5-4.0 mm. long, 1-nerved, both 
glumes ovate, blunt; lemmas 3.5-5.0 mm. long, oblong, blunt, conspicuously 7-nerved, 
scabrid on the nerves, with a purple band below the whitish, membranaceous apex; palea 
nearly as long as the lemma, glabrous, with thickened keels, the apex blunt; anthers 3, 
0.8-1.5 mm. long, yellow or rarely purplish. Chromosome number n = 20. 

This European species has not previously been reported from the 
western hemisphere. At the spot where we collected it, it was growing 
in a moist meadow along with Poa trivialis, another European species. 
It is probable that this species, like a number of others from highland 
pastures, represents a survival from accidental introduction in Euro- 
pean pasture seed mixtures. The following is our only collection: Car- 
tago, Hacienda Las Virtudes, SE of Volcan Irazu, 2,650 m., 14 Feb- 
ruary 1969, Pohl & Davidse 11715. 

GOUINIA Fournier 

REFERENCE: J. R. Swallen, The grass genus Gouinia. Amer. J. Bot. 
22:31-41. 1935. 

Caespitose perennial grasses; inflorescence a terminal panicle, the branches mostly 
simple, the spikelets pedicellate in 2 rows along the lower side of the slender branches. 
Spikelets with 2 or more florets, disarticulating above the glumes and between the 
florets; glumes 1-several-nerved, shorter than the spikelets; lemmas 3-nerved, lanceo- 
late, long awned from the acuminate apex, ciliate on the callus and nerves; rachilla 
slender, the internodes long; palea bidentate or awned, glabrous or pubescent. 

The genus, containing 13 species of tropical American grasses, is 
related to Leptochloa. (Chloridoideae: Eragrosteae.) 

Gouinia virgata (Presl) Scribn., Bull. U.S.D.A. Div. Agrost. 4:10. 
1897. Bromus virgatus Presl, Rel. Haenk. 1:263. 1830. Figure 87. 

Culms erect, 30-150 cm. tall, unbranched, glabrous, solid, pithy; nodes glabrous; 
sheaths slightly keeled above, shorter or longer than the internodes, glabrous or slightly 
hispid about the collar and base of the blade; ligule a ciliate membrane, 0.5-1.5 mm. long; 
blades up to 25 cm. or more long, 4-15 mm. wide, glabrous, tapering to a narrow base, 
margins scabrous. Panicle 10-15 cm. long, open, with few, solitary, mostly simple 
branches, stiffly spreading, 8-20 cm. long, spikelets lying parallel to the lower sides of 
the branches; pedicels 1-4 mm. long, angular. Spikelets 10-12 mm. long, excluding the 
awns, slender; disarticulation above the glumes and between the florets; first glume 




FIG. 87. Gouinia virgata. A, panicle; B, glumes, C, floret. 



248 



BURGER: FLORA COSTARICENSIS 249 

3.9-5.2 mm. long, 3-4-nerved, lanceolate; second glume 5.7-7.2 mm. long, 5-7-nerved, 
narrowly ovate; florets 2-3; lemmas 8-10 mm. long, lanceolate, acuminate, with a sharp 
bearded callus, the nerves and margins silky-ciliate on the lower half; awn from the tip, 
8-15 mm. long; upper florets shorter than the lowermost; palea 7-8 mm. long, silky-ciliate 
on the keels; anthers 3, 0.5-0.6 mm. long. Chromosome number n = 20 from Costa Rican 
specimens. 

Open forests near the Pacific Ocean, elevations below 100 m.; 
Cuajiniquil and Puerto Castillo, Hacienda Murcielago; Finca la 
Pacifica, Canas, Isla de Chira. October to January. Mexico to 
Guanacaste; Colombia to Peru and Ecuador; Cuba and Haiti. 

GYMNOPOGON Beauvois 

REFERENCE: J. P. Smith, Jr., Taxonomic revision of the genus 
Gymnopogon (Gramineae), Iowa State Univ. J. Sci. 45:319-385. 1971. 

Perennial or annual caespitose or rhizomatous grasses; culms simple or sparingly 
branched; leaf blades lacking a midrib, usually stiffly spreading. Inflorescence a panicle 
of several erect or spreading slender spikelike racemes; rachis of racemes triquetrous; 
spikelets alternating in 2 rows on 2 sides of the rachis and parallel to it. Spikelets 
1-2-flowered, the ultimate floret reduced to a thin awnlike body; disarticulation above 
the glumes; glumes 1-nerved, narrow, acuminate, keeled, both longer than the florets; 
lemma very faintly 3-nerved, its apex minutely bifid, usually bearing an awn that arises 
below the tip; palea 2-nerved, equal to the lemma; rachilla prolonged above the fertile 
floret and usually bearing a slender rudiment; caryopsis terete to angular. 

Gymnopogon is a small genus of about 13 species, confined to warm 
regions of the western hemisphere, with one species in Southeast Asia. 
The genus is closely related to Chloris, differing mostly in the stiff leaf 
blades, lacking midribs, the long, equal glumes, and the absence of a 
well-developed sterile upper floret. (Chloridoideae: Chlorideae.) 

Gymnopogon fastigiatus Nees, Agrost. Bras. 430. 1829, ssp. fas- 
tigiatus. Figure 88. 

Caespitose perennial; culms glabrous, erect to spreading, 35-80 cm. long, simple or 
sparingly branched from the middle nodes; sheaths glabrous except for sparse auricular 
pilosity at the throat; ligule a minute ciliolate membrane, ca. 0.1-0.2 mm. long; leaf 
blades glabrous, flat or involute, 2.0-4.5 cm. long, 1-4 mm. wide, subcordate at the base, 
stiffly ascending. Peduncle included or exserted up to 7 cm.; inflorescence a raceme of 
3-11 spikes, each 3-7 cm. long, spikelet-bearing to the base, ascending; axis triquetrous, 
scabrous. Spikelets 1-flowered; glumes subequal, acuminate, 1-nerved, the keel scab- 
rous; lemma faintly 3-nerved, glabrous on the back and sides, the margins pubescent, 
long-pilose at the summit; apex bifid, bearing a tortuous awn 8-15 mm. long from just 
below the bifid tip; palea membranaceous, 2-nerved; rachilla segment nearly as long as 
the lemma, lying between the keels of the palea, lacking a rudimentary second floret; 
anthers 3, ca. 0.7 mm. long; caryopsis 1.3-1.8 mm. long. Chromosome number n = 20. 




FIG. 88. Gymnopogon fastigiatus ssp. fastigiatus. A, inflorescence; B, portion of a 
spike; C, floret with prolonged rachilla internode. 

250 



BURGER: FLORA COSTARICENSIS 251 

Rare; in steep gullies, savannas of Boruca; reported from this area by 
Standley. The following is the only recent specimen: Puntarenas, 
Savanas de Boruca, elevation 380 m., P. & D. 11614. Blooming during 
the short days of the dry season. Costa Rica, Panama, northern South 
America from Colombia to Bolivia and Brazil. 

GYNERIUM Humboldt & Bonpland 

REFERENCE: H. J. Conert, Die Systematik und Anatomic der Arun- 
dineae, Cramer Verlag. Weinheim. 208 pp. 1961. 

Giant rhizomatous perennial grasses, forming large colonies; culms erect to arching, 
solid and semi-woody, the lower parts clothed with bladeless sheaths, the upper end 
with a large fan-shaped cluster of distichous leaves; dioecious, the staminate and the 
pistillate plants frequently in separate colonies. Inflorescence a very large terminal 
panicle borne on an elongated solid peduncle, the branches drooping along the rachis; 
pistillate panicles plumose; spikelets laterally compressed, disarticulating above the 
glumes and between the florets, usually 2-flowered. (Arundinoideae: Arundineae.) 

Gynerium sagittatum (Aubl.) Beauv., Ess. Nouv. Agrost. 138. 
1812. Saccharum sagittatum Aubl., PI. Gui. 1:50. 1775. Figure 89. 

Culms up to 10 m. tall, 2-5 cm. thick, simple or with extravaginal branches; leaf blades 
with a conspicuous midrib, 40-200 cm. long, 2-8 cm. wide, cottony on the midrib above 
the base, very scabrous on the margins; ligule a minute ciliolate membrane; nodes level 
with surface of the culm, glabrous. Peduncle 1 m. or more long, 1 cm. or more in 
diameter, smooth; panicles up to 1.5 m. long, the very slender branches emerging from 
the rachis in clusters, drooping along the rachis; spikelets pedicellate, in dense clusters 
along 3rd- or 4th-order branches. Pistillate spikelets: 8-10 mm. long, plumose; first 
glume 1-nerved, narrow, hyaline, ca. 3 mm. long; second glume longer than the florets, 
linear, faintly 3-nerved, 7-10 mm. long, light brown, thinly membranous, the upper 
two-thirds with inrolled margins, the keel recurved. After the fall of the florets, the 
glumes may also disarticulate. Florets 2; disarticulation at the base of the rachilla joints; 
lowermost lemma ca. 5 mm. long, the upper shorter; lemmas tapering into a slender 
inrolled awnlike beak, abundantly long-silky hairy on the basal half, the beak portion 
glabrous; callus bearing short erect hairs; palea ca. 1 mm. long, linear, glabrous except 
at the tip; lodicules 2, truncate; pistil with 2 terminal styles, terminating in feathery 
purple stigmas; staminodia may be present. Staminate spikelets: not plumose, ca. 3 mm. 
long, laterally compressed, disarticulating above the glumes and at the base of the upper 
floret; glumes about equal, 2 mm. long, 1-nerved, lanceolate, hyaline, brownish; lemmas 
2.0-2.5 mm. long, narrowly ovate, 1-nerved, purplish, sparsely puberulent at the base or 
occasionally with a few long hairs on the upper portion; palea blunt, nearly as long as the 
lemma; lodicules 2, truncate; anthers 2, 1.5-2.0 mm. long, yellow. A rudimentary ovary 
may be present. Chromosome number n = 22 from Costa Rican specimens. 

This species forms conspicuous large colonies along the margins of 
major streams and occasionally elsewhere, from sea level up to about 
1,100 m. The stems are harvested in large quantities and used in rustic 
construction and as banana props. Blooming is apparently yearlong. 




FIG. 89. Gynerium sagittatum. A, panicle; B, branchlet from a pistillate panicle; C, 
pistillate spikelet; D, branchlet from a staminate panicle; E, staminate spikelet. 



252 



BURGER: FLORA COSTARICENSIS 253 

Southern Mexico to Peru and northern Paraguay and Brazil; West 
Indies. Common name: Cana brava. 

HACKELOCHLOA Kuntze 

Caespitose, much-branched annual; inflorescences numerous, terminal and axillary 
solitary dorsi ventral pedunculate rames, exserted in clusters from the middle and upper 
sheaths; spikelets paired at each node of a flat disarticulating rachis; sessile spikelet of 
each pair spheroidal, rigid, the first glume much inflated, the upper portion round, 
blackish, its surface covered with square pits in transverse rows, its margins clasping 
the edges of the united rachis joint and pedicel, the base smooth and white, contracted; 
second glume appressed to the rachis joint, oblong, blunt, slightly keeled, chartaceous, 
3-nerved; flower perfect. Pedicellate spikelet very different from the sessile one and 
larger, its first glume flat, ovate, acute, green and herbaceous, many-nerved, clasping 
the margins of the second glume by 2 flanges borne near the margins on the inner side; 
second glume folded, strongly wing-keeled, as long as the first; inner parts usually 
absent. Occasional spikelets may possess sterile lemma, fertile lemma and palea, and a 
staminate flower. All the inner bracts are hyaline and nerveless. 

One species, native to the tropics of the Old World but widespread in 
the warmer regions of both hemispheres. (Panicoideae: An- 
dropogoneae.) 

Hackelochloa granularis (L.) Kuntze, Rev. Gen. PL 2:776. 1891. 
Cenchrus granularis L., Mant. PI. 2:575. 1771. Rottboellia granularis 
(L.) Roberty, Monogr. Androp. 79. 1960. Figure 90. 

Tufted, much-branched annual; erect, often with prop-roots; culms from very short to 
120 cm. long, solid, pithy, more or less pustulose-hispid, especially toward the apex of 
the internodes; sheaths much shorter than the internodes, inflated, keeled, the margins 
silky, the surface prominently pustulose-hispid; ligule arched, a ciliate membrane 1.0-1.5 
mm. long; leaf blades flat, 2-20 cm. long, 4-15 mm. wide, pustulose-hispid on both 
surfaces and on the margins. Peduncles bracted, arising in small groups from all the 
middle and upper nodes of the culms, slightly exserted; rames slender, stiff, 7-15 mm. 
long. Spikelets paired, the sessile ones in 2 rows alternating along one side of the rachis, 
the pedicellate ones on the opposite side. Sessile spikelets 1.3-1.7 mm. long, falling 
attached to the rachis joint, pedicel, and pedicellate spikelet; first glume rigid, sub- 
spherical or turbinate, its opening completely closed off by the chartaceous second 
glume; second glume 0.8-1.0 mm. long; fertile lemma and palea hyaline, nerveless, ca. 
0.9 mm. long; flower perfect; anthers 0.2-0.3 mm. long. Pedicellate spikelet 1.5-2.0 mm. 
long. Chromosome number n = 1 from Costa Rican specimens. 

Open dry weedy areas, common at low elevations and ascending to 
1,100 m.; both Caribbean and Pacific slopes; particularly common in 
Guanacaste. July to December. This species occurs in the western 
hemisphere as an introduction, from southern United States through 
Central America; Caribbean Islands. 

This peculiar grass is at once recognizable by the tiny spheroidal, 






FIG. 90. Hackelochloa granularis. A, B, two views of a spikelet pair; C, flowering 
culm. 



254 



BURGER: FLORA COSTARICENSIS 255 

blackish, pitted, fertile spikelets. The sheaths are pungent-bristly to 
the touch. 

HIEROCHLOE R. Brown 
Nomen Conservandum 

Rhizomatous perennials; culms simple; inflorescence a terminal panicle; spikelets of 3 
florets, disarticulating only above the subequal enlarged membranaceous glumes, the 
florets remaining attached to each other; lower 2 florets subequal, longer than the fertile 
floret, staminate or neuter; lemmas 5-nerved, usually awned below the tip or from the 
back; palea usually present (absent in our species); stamens, if present, 3, the anthers 
large; terminal floret with a blunt, 3-5-nerved lemma, awnless or nearly so; palea some- 
what shorter than the lemma, 1-nerved; stamens 2, usually rudimentary; stigmas 2; 
plants with the odor of coumarin. 

A small genus of Arctic, alpine and cool temperate grasses, mostly in 
the northern hemisphere but extending to South America. The sweet 
vanilla-like odor of the plants, due to the presence of coumarin, aids in 
their recognition. (Pooideae: Phalarideae.) 

Hierochloe davidsei Pohl, Iowa State J. Res. 47:71. 1972. Figure 
91. 

Rhizomatous perennial; culms erect, 30-60 cm. tall, unbranched, glabrous, hollow, 2-3 
mm. thick, arising singly or in small clumps from slender rhizomes; the rhizomes up to 9 
cm. long, often giving rise to leafy innovations; leaves 5-7 per culm; lower sheaths short 
and overlapping, the upper one or two much shorter than the internode, strongly ribbed, 
glabrous or occasionally retrorsely pilose, especially near the apex; ligules 1.5-5 mm. 
long, the upper ones longer than the lower, whitish, membranaceous, densely retrorsely 
pilose on the outer surface, truncate; leaf blades 5-8 mm. wide; 6-15 cm. long, the 
mid-culm blades largest, all rather blunt, pilose above; peduncle 10-15 cm. long, slender, 
erect, glabrous; inflorescence a single narrowly cylindrical terminal panicle, sometimes 
slightly lobulate below, 3-11 cm. long, the branches erect; pedicels 1-3 mm. long, slightly 
pilose; spikelets 5.5-6.5 mm. long, ovate, laterally compressed, brownish; glumes thin 
and membranaceous, ovate, acute, overlapping, the first 4-4.5 mm. long, 1-nerved, the 
second 5.5-6.5 mm., 3-nerved; florets 3; lower 2 florets sterile, lacking flower and palea, 
both ca. 5 mm. long; sterile lemmas 5-nerved, brownish, ciliate; first lemma with a short 
straight awn born ca. 1 mm. below the lobed apex and reaching to the tip; second lemma 
similar, but bearing a bent awn attached slightly below the middle of the lemma, below a 
lobed apex; awn 4-5.5 mm. long, twisted below, exserted laterally from the glumes 1-2 
mm.; fertile lemma 3 mm. long, thin and membranaceous, glabrous, 5-nerved, blunt, 
cucullate, awnless, or with a short straight awn, bifid at the apex; palea about equal, 
oblong, acute; anthers 2, ca. 1.5 mm. long, yellow; lodicules minute, evidently function- 
less. 

Chromosome number n = 28, determined from microsporocytes of 
the type: Prov. de San Jose, Paramo along Carretera Interamericana 
at km. 86, elevation 3,030 m., 23 August 1968, Pohl & Davidse 11004. 




FIG. 91. Hierochloe davidsei. A, blooming plant; B, spikelet; C, two lower sterile 
florets and fertile terminal floret. 



256 



BURGER: FLORA COSTARICENSIS 257 

This species is similar to H. mexicana, from which it differs in the 
following characteristics: 

Character H. davidsei H. mexicana 

leaf blade LAV ratio 11/1-12/1 20/1-30/1 

ligule very pilose glabrous 

lower 2 florets without flower and often with flower 

palea and palea 

anther length (mm.) 1.5 4 

In having sterile lower florets, this species resembles species of 
Anthoxanthum. The latter genus, however, has a basic chromosome 
number of 10, and the spikelets have very unequal glumes. Hierochloe 
davidsei has a basic chromosome number of X = 7 (n = 28) and sub- 
equal glumes. Certain specimens from Guatemala approach the Costa 
Rican species, but have anthers 2.5-3 mm. long and are probably best 
assigned to H . mexicana on other characters. This species is named for 
Gerrit Davidse, who discovered the plants. It is known from the type 
locality and from La Asuncion (Burger & Gomez 7936) and Chirripo 
Grande (Burger & Gomez 8212). It should be looked for elsewhere on 
the high paramos. Elevations 3,000-3,450 m. Blooming in August from 
the three known specimens. 

HOLCUS Linnaeus 

Caespitose or rhizomatous perennials; inflorescence a terminal panicle; spikelets com- 
pressed and keeled, 2-flowered; glumes equal, longer than the florets; disarticulation 
below the glumes; florets similar, but the lower one with a perfect flower, the upper 
staminate; upper lemma bearing a short, thick awn. (Pooideae: Aveneae.) 

Holcus lanatus L., Sp. PL 1048. 1753. Figure 92. 

Caespitose perennial; culms 20-100 cm. tall, erect from decumbent bases, unbranched, 
hollow and thin-walled, velutinous; nodes velvety; leaves 3-5 per culm; sheaths mostly 
overlapping; ligules 1.5-3 mm. long, membranaceous, decurrent on the sheaths, ciliolate, 
puberulent on the back; blades soft, grayish-green, velutinous, 4-20 cm. long, 3-10 mm. 
wide. Panicle solitary, contracted or lax, cylindrical to pyramidal, pale or pinkish or 
purplish. Spikelets closely arranged, overlapping, short-pedicellate, strongly com- 
pressed and keeled; glumes about equal in length, 4.0-4.5 mm. long, overlapping; first 
glume ovate, 1-nerved, second broadly ovate, 3-nerved; both ciliate on nerves and keel, 
puberulent on the internerves; florets 2, smooth and shining, completely hidden in the 
glumes; lower floret awnless, the upper with a short, hook-shaped awn from just below 
the apex; lemmas 2.0-2.3 mm. long, faintly 3-nerved; paleas slightly shorter than the 
lemmas, scabrid on the keels; anthers 3 in each floret, purplish, 1.7-2.2 mm. long. 
Chromosome number n = 1 from Costa Rican specimen. 



B 





FIG. 92. Holcux lanatus. A, panicle; B, spikelet; C, florets. 
258 



BURGER: FLORA COSTARICENSIS 269 

Pastures, open areas, roadsides; common in moist areas from 1,600- 
3,200 m. elevation, Cordillera Central and Cerro de la Muerte. 
Blooming is probably yearlong. This species is native in Eurasia and 
northwest Africa. It is widely naturalized in temperate North 
America. In Costa Rica, it was introduced as a forage crop, but is 
probably little used as such now. 

HOMOLEPIS Chase 

Stoloniferous grasses; inflorescence a terminal panicle. Disarticulation below the 
glumes; spikelets lanceolate, acuminate, dorsally compressed; glumes concealing the 
florets, subequal or the first somewhat longer than the second, its margins covering the 
edges of the second; first glume 7-9-nerved, ovate; second glume 7-nerved; sterile lemma 
7-nerved, strongly ciliate between the marginal nerves, its palea small, membranaceous; 
fertile floret chartaceous, acuminate, the lemma obscurely nerved, glabrous and shining, 
with thin exposed margins overlapping the margins of a palea of similar length and 
texture. (Panicoideae: Paniceae.) 

Homolepis aturensis (H.B.K.) Chase, Proc. Biol. Soc. Wash. 
24:146. 1911. Panicum aturense H.B.K., Nov. Gen. & Sp. 1:103. 1816. 
Figure 93. 

Duration indefinite; plants extensively stoloniferous; erect or ascending floriferous 
branches 20-50 cm. long arising from the stolons; culms glabrous, hollow, 1-2 mm. thick; 
nodes glabrous; sheaths usually shorter than the internodes, glabrous or pilose, silky- 
ciliate on the margins, keeled; ligule a minutely ciliate membrane, 0.4-0.7 mm. long; a 
puberulent line across the collar; blades cordate above a brief pseudopetiole, flat, 4-12 
cm. long, 7-20 mm. wide, glabrous to pilose or velutinous on the surfaces; peduncle 
included or exserted up to 12 cm.; uppermost leaf blade much reduced; panicles terminal 
on the culms or on leafy branches, narrowly elliptical, 6-9 cm. long, 2-5 x longer than 
wide; spikelets on slender pedicels, rather crowded, 7.0-7.7 mm. long; first glume 7-9- 
nerved, ovate, the margins overlapping the edges of the second; second glume 6.4-6.8 
mm. long, 7-nerved, the margins ciliate near the base; sterile lemma 7-nerved, 5.2-6.8 
mm. long, 7-nerved, strongly silky-ciliate between the marginal pairs of nerves; fertile 
lemma 4.8-6.0 mm. long, lanceolate, the nerves faint, its palea similar; anthers 3, purple, 
1.3-1.6 mm. long. Chromosome number n = 10 from Costa Rican material. 

Moist pastures, shaded roadsides, sea beaches, from sea level to 
1,200 m. elevation, on both Caribbean and Pacific slopes. June to 
March. Southern Mexico to Bolivia and Brazil. 

HYMENACHNE Beauvois 

Aquatic or paludose perennials of tall stature; culm internodes filled with spongy 
aerenchyma. Inflorescence a dense narrowly cylindrical or spikelike terminal panicle. 
Spikelets lanceolate-acuminate, dorsally compressed; first glume 1-3-nerved, much 
shorter than the spikelet, a definite internode of the rachilla between the first and second 
glumes; second glume and sterile lemma 3-5-nerved, subequal, both longer than the 




FIG. 93. Homolepis aturensis. A, panicle; B, stolon with leafy shoots; C, two views of 
a spikelet. 



BURGER: FLORA COSTARICENSIS 261 

perfect terminal floret; sterile lemma lacking a pa lea; fertile lemma lanceolate, chartace- 
ous, smooth and glabrous, very faintly nerved, its margins thin, not inrolled; palea 
nearly as long as the lemma and of similar texture. 

A genus of about 10 species of New World and Asiatic tropics, 
closely related to Sacciolepis and differing from it in having solid in- 
temodes. (Panicoideae: Paniceae.) 

KEY TO SPECIES OF Hymenachne 

la. Spikelets 3.5-5.5 mm. long; second glume and sterile lemma 5-nerved, acuminate; 

panicles spikelike H. amplexicaulis 

Ib. Spikelets 2.5-2.9 mm. long; second glume and sterile lemma 3-nerved, acute; panicle 

narrowly cylindrical, tapering, with ascending branches H. donacifolia 

Hymenachne amplexicaulis (Rudge) Nees, Agrost. Bras. 276. 
1829. Panicum amplexicaule Rudge, PI. Gui. 1:21, pi. 27. 1805. Figure 
94. 

Tall perennial, the culms to 3.5 m. long, arising from long decumbent rooting bases; 
culms thick and spongy, the interior filled with stellate aerenchyma, glabrous; nodes 
glabrous, with swollen sheath pulvini; sheaths much shorter than the internodes, gla- 
brous, or the margins papillose-ciliate; ligule a thin brownish membrane, 1.0-2.5 mm. 
long; blades soft, flat, glabrous, 15-33 cm. long, 12-28 mm. wide, the margins strongly 
scabrous, pustulose-ciliate on the cordate-clasping basal lobes. Peduncle glabrous, usu- 
ally included in the upper sheath; panicles spikelike, solitary, 10-40 cm. long, 1-2 cm. 
thick, dense, sometimes lobed near the base; spikelets densely crowded, short-pedicel- 
late, ascending along the short erect branches of the panicle. Spikelets lanceolate, 
acuminate; 3.5-5.5 mm. long, scabrous on the nerves; first glume 1.0-1.7 mm. long, 
ovate, 3-nerved, sometimes caudate; second glume 5-nerved, 2.8-3.9 mm. long, caudate; 
sterile lemma 5-nerved, longer than the second glume, caudate, 3.6-4.6 mm. long, lack- 
ing palea or flower; fertile lemma shorter than the sterile lemma, 2.5-3.5 mm. long; 
anthers 3, 1.1-1.2 mm. long, yellowish or pinkish; caryopsis elliptical, tan, free from the 
floret. Chromosome number n = 10 from Costa Rican material. 

Marshes, ditches, lakes, riverbanks; occasional at low elevations 
from 20-850 m., mostly under 300 m., on both Caribbean and Pacific 
slopes. Apparently blooming yearlong. Southern Mexico to Argentina. 

Hymenachne donacifolia (Raddi) Chase, J. Wash. Acad. Sci. 
13:177. 1923. Panicum donacifolium Raddi, Agrost. Bras. 44:1823. 

Succulent perennial; culms 3-4 m. tall, from long decumbent rooting bases, un- 
branched above, 4-6 mm. thick, glabrous, solid, the interior filled with stellate aeren- 
chyma; nodes with swollen sheath pulvini; sheaths shorter than the internodes, gla- 
brous, the margin somewhat pustulose-ciliate; ligule a minute membrane, ca. 0.4-0.5 
mm. long; blades 25-27 cm. long, 27-40 mm. wide, glabrous, with cordate-clasping basal 
lobes, the margins scabrous. Peduncle included; panicles narrowly cylindrical, tapering 
to a narrow tip, the branches ascending, strict, the lower ones as much as 6 cm. long, the 
rachis exposed between whorls of branches. Spikelets short-pedicellate, densely clus- 
tered along the lower sides of the branches, 2.5-2.9 mm. long, lanceolate; first glume 
ovate, acute, 1-nerved, 0.9-1.1 mm. long; second glume 2.0-2.1 mm. long, lanceolate, 




FIG. 94. Hymenachne amplexicaulis. Blooming plant, rooting culm base. 



262 



BURGER: FLORA COSTARICENSIS 263 

acute, 3-nerved; sterile lemma 2.3-2.6 mm. long, lanceolate, acute, 3-nerved; fertile 
lemma 2.0-2.2 mm. long, narrowly ovate, obscurely nerved; palea about equal in length; 
anthers 3, 0.5 mm. long, purplish. The foliage has a deep green to olivaceous coloration. 
Chromosome number n = 20 from a Costa Rican specimen. 

Rare; elevations below 800 m.; riverbanks. General Valley near San 
Isidro (Skutch 3963), near San Vito de Java (Pohl & Davidse 11161). 
Southern Costa Rica, Panama; Cuba and Trinidad; Bolivia to Argen- 
tina. 

HYPARRHENIA Andersson in Stapf 

Perennial caespitose grasses; inflorescence usually complex, of numerous individually 
pedunculate spathaceous partial inflorescences, each of a pair of nearly conjugate rames 
at the tip of a slender peduncle; rames, or some of them, having a basal pair of sessile 
awnless spikelets that are staminate or sterile, followed by 1 or more spikelet pairs, each 
consisting of 1 sessile, awned, perfect-flowered spikelet and 1 pedicellate, nearly awn- 
less, usually staminate spikelet; rame terminating in a triad of 1 sessile spikelet and 2 
pedicellate spikelets. Spikelets dorsally compressed; glumes equal, lanceolate, the first 
flat on the back, 7-9-nerved, its margins incurved over the edges of the second glume and 
slightly keeled and ciliolate near the bifid tip; second glume 3-nerved, bulging on the 
back; florets usually 2, shorter than the glumes and completely concealed by them; lower 
lemma thin, membranaceous, faintly nerved; upper lemma in staminate or sterile 
spikelets similar to the first; upper lemma in perfect-flowered spikelets very narrow, 
membranaceous, 2-lobed at the tip, scarcely wider than the broad flat base of the stout, 
twisted and geniculate exserted awn. Disarticulation usually above the basal pair of 
spikelets and at the tip of each internode of the flattened, ciliate rachis, the spikelet pairs 
or triads falling as units. (Panicoideae: Andropogoneae.) 

Hyparrhenia is a large genus of more than 75 species, nearly all 
confined to tropical and subtropical Africa, with a few species, some 
introduced, in tropical and subtropical America. The genus is closely 
related to Andropogon, differing mostly in the rounded and incurved, 
not keeled, margins of the first glume, and in the presence of a basal 
pair of sessile, equal, and usually staminate or sterile spikelets. 

KEY TO SPECIES OF Hyparrhenia 

la. Rames of each pair ascending, diverging at an acute angle from each other; spikelet 
pairs usually 5 or more per rame; common cultivated forage grass, widely es- 
caping H. rufa 

Ib. Rames of each pair strongly reflexed away from each other; spikelet pairs or triads 
usually 1-2 per rame; rare; Boruca H. bracteata 

Hyparrhenia bracteata (Willd.) Stapf in Prain, Fl. Trop. Africa 
9:360. 1919. Andropogon bracteatus Willd., Sp. PL ed. 4. 914. 1806. 
Figure 95. 

Perennial, in dense tufts; plants up to 2.5 m. tall, caespitose; culms erect, unbranched 
except in the inflorescence, up to 5 mm. thick, solid or with a small lumen, glabrous or 




FIG. 95. Hyparrhenia bracteata. A, compound inflorescence; B, a rame and its 
spatheole; C, triad of a sessile, perfect-flowered spikelet and two awnless, pedicellate 
staminate spikelets. 



264 



BURGER: FLORA COSTARICENSIS 265 

appressed-silky below the contracted nodes; basal leaf sheaths keeled, overlapping; 
sheaths appressed-hirsute; ligule a firm brown membrane, 1-3 mm. long, densely short- 
ciliate on the margin; leaf blades up to 5 mm. wide, the margins revolute, lower surface 
appressed-hirsute like the sheath, upper surface glabrous or puberulent; midrib wide, 
flat above. Inflorescence an elongate virgate mass, up to 50 cm. long, much branched 
with several orders of ascending branches, each with a bladeless spathe; ultimate 
inflorescences borne on slender, heavily papillose-hirsute peduncles, each subtended by 
a spatheole longer than the peduncle, which protrudes laterally from it; rames paired, 
reflexed at the tip of the peduncle, a dense tuft of elongated glassy hairs between them; 
one rame subsessile and with a pair of sessile awnless staminate spikelets at its base; 
rachis bearing an oblong bract just above the pair of staminate spikelets; disarticulation 
just above this bract, the remainder of the rame usually a triad of one sessile perfect- 
flowered awned spikelet, accompanied by 2 pedicellate awnless or awn-tipped staminate 
spikelets. Callus of the sessile spikelet slender, pointed, heavily bearded; pedicels thin 
and flat, heavily bearded on the margins, extremely oblique at their tips. Basal awnless 
spikelets 5.0-5.5 mm. long, lanceolate; first glume 7-nerved, its edges infolded, slightly 
keeled and ciliolate near the tip; second glume 4.5-5.0 mm. long, 3-nerved; lower lemma 
membranaceous, 4.0-4.2 mm. long, firm, ciliate, 1-nerved; upper lemma 3.0-3.2 mm. 
long, ciliate; lodicules 2, ciliate; anthers 0-3, ca. 2 mm. long. Sessile spikelet of the 
terminal triad 5.5-6.5 mm. long, lanceolate; first glume ca. 7-nerved, grooved on both 
sides of the midrib, bifid at the tip, the teeth acute, keels ciliolate near the tip; second 
glume convex, lanceolate, 3-nerved, awn-tipped; sterile lemma 3.5-4.5 mm. long, mem- 
branaceous, faintly nerved; fertile lemma scarcely wider than the flattened awn base; 
awn ca. 3 cm. long, geniculate, the 2 basal segments strongly twisted and hispid; anthers 
3, yellow, 1.5 mm. long; stigmas purple. Pedicellate spikelets similar, ca. 4.5 mm. long; 
first glume with an awn up to 1.8 mm. long, lower lemma ca. 2.5 mm. long; upper lemma 
3.5-4.0 mm. long; anthers 3, 2.0-3.0 mm. long. Second rame of the pair similar to the 
first, but lacking the basal pair of sessile spikelets. Occasionally, 1 rame may contain 
more spikelet pairs. 

Dry hilly savannas, Boruca and Buenos Aires; elevation 380-480 m.; 
rare. December. Southern Mexico to Brazil and Paraguay. Tropical 
Africa. Willdenow cited a specimen from Cumana, Venezuela, and 
credited the species to Humboldt and Bonpland; however, he indicated 
that the description was his own and that he had seen a dry specimen. 

Hyparrhenia rufa (Nees) Stapf in Prain, Fl. Trop. Africa 9:304. 
1919. Trachypogon rufus Nees, Agrost. Bras. 345. 1829. Figure 96. 

Perennial; densely caespitose, forming large clumps with numerous innovations and 
elongate drooping basal leaves; culms mostly 1-2 m. tall, unbranched except in the 
inflorescence, internodes round, glabrous, solid or with a small lumen; nodes contracted, 
glabrous or slightly puberulent, a swelling just above the node; leaf sheaths shorter than 
the internodes, keeled near the apex, from glabrous to marginally papillose-hirsute 
above, rarely hirsute all over; ligule a firm brownish membrane, 1.0-2.5 mm. long; blades 
flat, narrow at the base, glabrous, or hirsute above, especially near the base; basal 
blades up to 70 cm. long, 7 mm. wide, the culm blades smaller. Inflorescence a large 
compound mass, up to 50 cm. long, open, composed of numerous axillary branches, the 
ultimate inflorescences being paired slender rames borne on slender weak hairy pedun- 
cles exserted from bladeless sheaths. One of the pair of rames subsessile at the tip of the 




FIG. 96. Hyparrhenia rufa. A, compound inflorescence; B, a pair of awnless spikelets 
from the base of a rame; C, pair with sessile, awned spikelet and pedicellate awnless 
spikelet. 



266 



BURGER: FLORA COSTARICENSIS 267 

peduncle, the other on a short rachis, one or both with a pair of equal awnless spikelets 
at the base. Rames 1-4 cm. long, with up to 8 pairs of spikelets, the terminal segment of 
the rachis bearing one sessile spikelet and a pair of equal awnless pedicellate ones. 
Rachis internodes, pedicels, and spikelets heavily bearded with rusty colored ascending 
hairs; rachis disarticulating at the base of the internodes and the tips of the pedicels; 
internodes thin, flat, ca. 3 mm. long. Basal pair of spikelets usually awnless, subequal, 
4.5-5.5 mm. long, lanceolate in outline; first and second glumes equal in length, the first 
flattened on the back, the edges inrolled but not keeled except near the ciliate bidentate 
tip; nerves 9-11; second glume 3-nerved, tapering to the tip; lower lemma empty, 1-3- 
nerved, hyaline, ciliate; upper lemma similar, enclosing a staminate flower with 2 
lodicules and 3 yellow to reddish anthers, 2.5-3.0 mm. long. Succeeding pairs of spikelets 
dimorphic, the sessile spikelet with a conspicuous geniculate awn, the 2 basal segments 
twisted and appressed-hispid, the terminal segment thin and straight; pedicellate 
spikelet 3.7-5.5 mm. long, lacking an awn but similar in shape to the other. Sessile 
spikelet 3.7-4.5 mm. long, with an empty lower lemma, the upper lemma very narrow, 
membranaceous, 2-lobed at the apex, the wide flat awn arising between the lobes; 
lodicules 2, truncate; anthers 3, yellow or reddish, usually smaller than those of the basal 
pair; stigmas purple. Pedicellate spikelets sterile or with minute staminodes. 

Abundant in open areas, pastures, and savannas; elevations up to 
900 m.; widely cultivated for forage and freely escaping to the wild, 
becoming a dominant species in Guanacaste. The principal season of 
bloom is from late October to December, when the tall culms develop 
synchronously over large areas. During most of the rest of the year, 
the plants remain vegetative, producing much basal foliage but only 
scattered and somewhat dwarfed blooming culms. Hyparrhenia rufa is 
of African origin, but is now widespread in the American tropics; 
Mexico to Brazil. Common name: Jaragud. 

HYPOGYNIUM Nees 

Caespitose perennial grasses; inflorescence a compound mass of numerous individually 
spathaceous racemes, each of few pairs of similar awnless spikelets; rachis internodes 
thin, disarticulating at the nodes; racemes terminating in a single staminate spikelet; 
subsessile spikelet of each pair pistillate, with 2 stigmas and 3 minute staminodes; 
pedicellate spikelet of each pair staminate, with 3 fertile anthers; spikelets dorsally 
compressed, lanceolate, awnless; glumes equal in length, coriaceous, completely con- 
cealing the 2 florets; first glume flattened on the back, the margins sharply inflexed over 
the edges of the convex second glume; lower floret consisting of a thin membranaceous 
lemma, shorter than the glumes, lacking flower or palea; upper floret similar, consisting 
of a membranaceous lemma containing a pair of truncate lodicules and a staminate 
flower. 

A small genus of two species, one in tropical Africa and the other in 
the American tropics. The genus was formerly united with Andropo- 
gon, from which it differs in having both spikelets of the pair externally 
equal, awnless, and pedicellate, and also in the unisexual spikelets. 
(Panicoideae: Andropogoneae.) 



268 FIELDIANA: BOTANY 

Hypogynium virgatum (Desv.) Dandy, J. Bot. 69:54. 1931. An- 
dropogon virgatus Desv. in Hamil., Prodr. PI. Ind. Occ. 9:1825. Figure 
97. 

Perennial, caespitose in large dense tufts; culms erect, 95-165 cm. tall, unbranched 
except in the inflorescence, up to 4 mm. thick, glabrous; internodes mostly solid, filled 
with parenchyma or with a small lumen; nodes dark, glabrous, slightly contracted; basal 
leaf sheaths keeled and longer than the internodes, glabrous, the basal blades up to 90 
cm. long, 3 mm. wide, the upper leaves with sheaths shorter than the internodes and 
much smaller blades that are pilose on the upper surface near the ligule, erect and flat 
near the base, involute above; ligule an inverted U-shaped stiff membrane, less than 1 
mm. long. Inflorescence an elongated ellipsoidal compound mass, terminal on the main 
culms or axillary from upper leaf nodes, in total 15-40 cm. long, up to 6 cm. thick, 
repeatedly branching, each branch and the individual racemes subtended by a bladeless 
sheath or spathe. Individual racemes solitary on a short peduncle which is enveloped by 
a spatheole that envelops the lower portion of the raceme; racemes 1.0-1.5 cm. long, 
usually of 5-6 internodes, each bearing a pair of spikelets; rachis slender, scabrous, 
disarticulating at the bases of the internodes, bearing a solitary terminal staminate 
spikelet at the tip. Pistillate spikelet of each pair 2.8-3.1 mm. long, subsessile, on a 
thickish pedicel ca. 0.2 mm. long; first glume 2-3-nerved, hispid on the angles above; 
second glume 3-5-nerved; florets similar, the lemmas ca. 2.0 mm. long, staminodes 
minute; stigmas large, plumose, purple. Staminate spikelet similar to the pistillate 
spikelet, borne on pedicel ca. 1 mm. long; anthers 3, yellow or reddish, 1.1-1.2 mm. long. 
Chromosome number n = 10 from a Costa Rican specimen. 

Savannas at Buenos Aires; roadsides near San Isidro de El General. 
December to February. British Honduras and Guatemala; northeast- 
ern Nicaragua; Costa Rica to Argentina; West Indies. 

The plants are reddish in all their parts. Harlan (Rhodora 58:138. 
1956) has reported a chromosome number of n = 15 for a Brazilian 
specimen designated as H. spathifolius. 

ICHNANTHUS Beauvois 

REFERENCES: K. E. Rogers, A taxonomic study of the genus 
Ichnanthus (Gramineae), Section Foveolata Pilger, Unpubl. Ph.D. 
Diss., Univ. of Tennessee. University Microfilms 69-16, 528. vii + 187 
pp. 1969. Michael Stieber, A revision of the genus Ichnanthus 
(Gramineae) based on the morphology and anatomy, Unpubl. Ph.D. 
Diss., Univ. of Maryland. University Microfilms 75-29, 136. 211 pp. 
1975. A. S. Hitchcock, The North American species of Ichnanthus, 
Contr. U.S. Natl. Herb. 22:1-12. 1920. 

Perennial, usually decumbent or creeping grasses; leaf blades flat, often ovate; ligule a 
membrane; panicles terminal and axillary. Spikelets usually paired and unequally 
pedicellate, more or less dorsally compressed, but the glumes keeled; disarticulation 
below the glumes; glumes and lower lemma membranaceous, strongly nerved, acute or 
acuminate; first glume shorter than the spikelet, 3-5-nerved; second glume and lower 




FIG. 97. Hypogynium virgatum. A, compound inflorescence; B, rame with base en- 
veloped in a spatheole; C, terminus of a rame with a single staminate spikelet; D, 
spikelet pair. 



270 FIELDIANA: BOTANY 

lemma subequal, acute or acuminate, as long as the spikelet, surpassing and mostly 
concealing the upper (fertile) floret; second glume 5-9-nerved; lower lemma similar, with 
a well-developed palea and often a staminate flower; upper floret cartilaginous or rigid, 
dorsally compressed, awnless, ovate or elliptical, smooth and shining; lemma with in- 
rolled margins, bearing on its lower curved margins depressed scars or winglike ap- 
pendages, these continued downward into a minute stipe (rachilla internode). These 
scars or wings are usually considered to be appendages of the rachilla internode, al- 
though they fall with the easily detached fertile floret. Palea flat, its margins covered by 
the inrolled edges of the lemma. 

The genus is common in moister parts of tropical America, and oc- 
curs in western Africa and tropical Asia as well. The plants usually 
occur in forests or forest margins, at low or middle altitudes. Ichnan- 
thus is only weakly differentiated from Panicum, the best mark of 
distinction being the scars or appendages of the upper (fertile) lemma. 
The plants are extremely variable, and two recent authors have esti- 
mated the number of species as 27 and over 100, respectively. Some 
species, in addition to their great morphological variation, exhibit sev- 
eral levels of polyploidy. Chromosomal abnormalities and aneuploidy 
are known as well. It is evident that the genus needs continued biosys- 
tematic study. Occasional plants of various species may have weirdly 
proliferated, greatly elongated spikelets with numerous sterile, over- 
lapping bracts, the whole resembling a multi-flowered spikelet of a 
pooid or chloridoid grass. (Panicoideae: Paniceae.) 

KEY TO SPECIES OF Ichnanthus 

la. Mature upper lemma, including basal stipe (rachilla) 2 mm. or less long; terminal 
panicles with lower branches more than 5 cm. long, usually rebranched; upper 

lemma usually rotated 90 within spikelets when mature /. pallens 

Ib. Mature upper lemma 2-3 mm. long; terminal panicles with branches less than 5 cm. 

long, mostly simple; upper lemma usually not rotated within mature spikelet . . 2 

2a. First glume narrowly triangular, 3-nerved, tapering gradually into a caudate 

tip, the length, including the awn, 6.5-9 x the folded width; peduncles very 

slender, arching, exserted up to 19 cm /. tennis 

2b. First glume ovate, 3-5-nerved, tapering abruptly to a cuspidate tip, length 
3.2-4.7 x the folded width; peduncles stiff, usually exserted 3-6 cm. 

/. nemorosus 

Ichnanthus nemorosus (Swartz) Doell in Mart., Fl. Bras. 2 (2):289. 
1877. Panicum nemorosum Swartz, Prodr. PL Ind. Occ. 22. 1788. For 
a detailed synonomy, see Stieber, I.e. Figure 98. 

Duration indefinite, probably perennial; plants creeping, forming patches, the culms 
rooting at the lower nodes and branching freely below; internodes 1.5 mm. or less thick, 
hollow, glabrous or papillose-pilose in lines or overall; nodes mostly bearded; sheaths 
shorter than the internodes, more or less papillose-pilose, especially on the margin; 
ligule a short-ciliate membrane, 0.5-1.3 mm. long; leaf blades flat, asymmetric at the 






FIG. 98. Ichnanthus species. /. nemorosus: A, flowering shoot; B, spikelet; /. tennis: 
C, flowering shoot; D, spikelet. 



271 



272 FIELDIANA: BOTANY 

sometimes subcordate base, mostly 2-7 cm. long, 7-12 mm. wide, usually ovate 3.5-7:1, 
more or less papillose-pilose to nearly glabrous. Terminal peduncle exserted 3-6 cm.; 
terminal panicle 3-5 cm. long, 1.5-3 cm. wide, open pyramidal, with few short branches; 
terminal panicle usually accompanied by a smaller axillary barely exserted one from the 
terminal sheath, and often a small axillary one from the sheath below. Spikelets paired, 
unequally pedicellate, few on one branch, appressed, green or purple, 3.0-4.5 mm. long, 
ovate; first glume 1.8-3.6 mm. long, 3- or rarely 5-nerved, acute or cuspidate, the length 
3.2-4.7 x the folded width; second glume 2.8-4.2 mm. long, ovate, acute, 5-nerved, 
sometimes with scattered weak hairs near the margin; lower (sterile) lemma 2.8-3.5 mm. 
long, ovate, acute, 5-nerved, enclosing a membranaceous palea at least three-fourths as 
long and usually a staminate flower with 3 stamens; rare individuals may have a pistillate 
lower flower; upper (fertile) lemma 2.1-2.6 mm. long, elliptic, blunt, cartilaginous, its 
lower margins scarred, the scars continued downward as wings on the short stipelike 
rachilla; palea similar and equal in length, its edges covered with the inrolled margins of 
the lemma; lodicules 2, truncate; anthers 3, yellow, 1.2-1.5 mm. long. 

Moist forests; 600-2,200 m. elevation; mountains from Guanacaste to 
the Panamanian Border. June to October. Southern Mexico to Argen- 
tina; West Indies. We have recorded several chromosome counts of n 
= 20 for this species, as well as an aneuploid count of n = 27, and have 
observed cases of abnormal meiosis as well. This species is weedy and 
displays a great deal of variation in leaf shape and pubescence. 

Ichnanthus pallens (Swartz) Munro ex Benth., Fl. Hongk. 414. 
1861. Panicum pallens Swartz, Prodr. Ind. Occ. 23:1788. Ichnanthus 
axillaris (Nees) Hitchc. & Chase, Contr. U.S. Natl. Herb. 18:334. 
1917. Panicum axillare Nees, Agrost. Bras. 141. 1829. Figure 99. 

Perennial, the plants mostly decumbent and creeping, or the culms ascending into 
brush and up to 2-3 m. long; lower nodes rooting; branching abundant; culms usually 
1.0-1.5 mm. thick, the internodes hollow, thick-walled; sheaths mostly shorter than the 
internodes, usually glabrous but with pilose upper margins; ligule a ciliate membrane, 
1-2 mm. long; leaf blades flat, thin, dark green, usually ovate 2.3:1-5:1, rarely to 9:1, 
asymmetric and subcordate at the base, usually glabrous or scabrid. Inflorescences 
1-several from the terminal sheath, one larger and longer-pedunculate than the other; 
axillary panicles usually present from several upper sheaths; panicles usually 5-10 cm. 
long, ovoid, the longest branch 5-7 cm. long, often somewhat congested, the larger 
branches secondarily branched, rather densely flowered, the spikelets appressed to the 
branches. Spikelets keeled, slightly laterally compressed, glabrous or scabrous, 3-4 mm. 
long, disarticulating entire, but the upper floret very weakly attached and frequently 
separating; first glume usually at least three-fourths as long as the spikelet, 3-nerved, 
triangular 3-4:1 as folded, acuminate; second glume and lower (sterile) lemma subequal 
or the glume slightly longer; second glume 5-nerved, the lateral pairs remote from the 
midrib, acuminate; lower lemma similar, enclosing a palea at least three-fourths as long 
and often a staminate flower with 3 stamens; upper (fertile) floret shorter than the 
glumes and lower lemma, 1.5-2.2 mm. long, elliptical, blunt, lemma cartilaginous, gla- 
brous, dorsally compressed, its margins inrolled over the edges of the palea of equal 
length; lower margins of lemma bearing depressed scarred areas, these extending 
downward to the stipelike attached rachilla internode; stamens 3, the anthers yellow, 




FIG. 99. Ichnanthus pollens. A, stoloniferous base; B, young panicle; C, mature 
panicle; D, spikelet; E, fertile floret, showing scars on basal lemma margins. 



273 



274 FIELDIANA: BOTANY 

0.8-1.0 mm. long. Fertile floret when mature often rotating 90 within the spikelet, its 
back visible from the side of the spikelet. 

Common in moist forested areas from near sea level to about 1,500 
m. elevation, most common at lower elevations; rain forest, forest 
margins, clearings, coffee and cacao plantations, usually in areas with 
some disturbance, on both Pacific and Caribbean slopes; rare in 
Guanacaste. Blooming mostly July to December. Central America to 
northern Argentina; West Indies. 

This species is somewhat weedy. The plants are astonishingly di- 
verse, but it appears quite impossible to select separable types. 
Chromosome numbers among our Costa Rican collections were n = 10, 
20, 27, ca. 30, and 30; however, no clear correlation was seen between 
ploidy level and morphological type. The two counts of n = 10 were 
from plants collected near sea level, and the higher counts were from 
greater elevations. 

Ichnanthus tenuis (Presl) Hitchc. & Chase, Contr. U.S. Natl. 
Herb. 18:334. 1917. Oplismenus tenuis Presl, Rel. Haenk. 319. 1830. 
See Stieber, I.e. for an extended synonymy. Figure 98. 

Duration indefinite, possibly annual; plants creeping, the lower nodes rooting; culms 
10-70 cm. long, branching freely; internodes very slender, elongated, hollow, glabrous or 
pubescent, especially in longitudinal stripes; nodes usually bearded; sheaths much 
shorter than the internodes; more or less papillose-pilose; ligule a short, thin membrane, 
long-ciliate, in total up to 1.5 mm. long; leaf blades flat, thin, ovate 3.5-7:1, asymmetrical 
at the subcordate base, mostly 2.5-5.0 cm. long, 6-13 mm. wide, the surfaces scabrous to 
heavily papillose-pilose. Peduncles very slender, arched, elongated, up to 19 cm. long, 
usually several from the terminal sheath, with others arising from the axils of most of 
the lower sheaths. Terminal inflorescence usually 2-7 cm. long, open, the branches 
usually solitary, ascending; spikelets mostly paired, unequally pedicellate, appressed 
along the usually simple branches. Spikelets 3.5-4.5 mm. long, disarticulating entire, 
narrowly ovate, acuminate; first glume 2.1-3.6 mm. long, 3-nerved, narrowly triangular, 
the length 6.5-9 x the folded width, caudate; second glume about as long as the spikelet, 
3.2-4.2 mm. long, 5-nerved, ovate, caudate, often bearing scattered weak slender hairs 
near the upper margins; lower (sterile) lemma similar, 2.6-3.5 mm. long, 5-nerved, 
enclosing a membranaceous palea at least three-fourths as long, usually with a staminate 
flower; upper (fertile) lemma elliptical, blunt, cartilaginous, light-colored, 1.9-2.6 mm. 
long, its lower margins with depressed scars that continue downward as wings onto the 
stipelike rachilla internode; margins inrolled over a palea of equal length; anthers 3, 
yellow, 0.8-1.5 mm. long. Chromosome numbers n = 10, 20 from Costa Rican specimens. 

Along trails and streams in forests, mostly at elevations up to 300 
m., but occasionally to 1,100 m., on both Pacific and Caribbean slopes. 
October to March. Southern Mexico to Brazil. The plants are some- 
what weedy. They are best recognized by the small leaves and slender, 
whiplike peduncles, and the caudate, pubescent spikelets. 



BURGER: FLORA COSTARICENSIS 275 

IMPERATA Cyrillo 

Rhizomatous perennials; inflorescence a dense cylindrical terminal panicle, the 
spikelets mostly concealed by long, silky hairs borne on the axis, branches, pedicels, and 
spikelets. Spikelets paired, alike, unequally pedicellate, disarticulating from the disklike 
apex of the pedicels; callus truncate, bearing a ring of numerous elongate silky hairs 
several times as long as the spikelets; spikelets narrowly ovoid in outline; glumes nearly 
equal or the first slightly shorter than the second, membranaceous, 3-7-nerved, nar- 
rowly triangular, bearing scattered long silky hairs; sterile lemma and fertile lemma 
much shorter than the glumes, hyaline and nerveless, their apices erose-jagged; stamen 
usually 1. 

A small genus of about seven species of warm climate grasses of both 
eastern and western hemispheres, related to Saccharum and Erio- 
chrysis. The plants are often regarded as weeds with little forage 
value. (Panicoideae: Andropogoneae.) 

KEY TO SPECIES OF Imperata 

la. Inflorescence 25-50 cm. long; culms 1-2 m. tall, leafy, bearing elongated leaf blades; 

spikelets 2.9-3.5 mm. long /. contructa 

Ib. Inflorescence 6-15 cm. long; culms up to 80 cm. tall, the foliage mostly near the base, 

the blades of stem leaves small; spikelets 3.5-4.5 mm. long /. brasiliensis 

Imperata brasiliensis Trin., Mem. Acad. Imp. Sci. St.- 
Petersbourg, Ser. 6, Sci. Math. 2:331. 1832. I. caudata Cyr. ex 
Chapm., Fl. S. U.S. ed. 2. 668. 1883. 

Perennial from scaly, creeping rhizomes; culms unbranched, 1 mm. thick, glabrous, 
25-75 cm. tall, the interior more or less filled with parenchyma; nodes more or less 
bearded with tufts of appressed elongated silky hairs; foliage mostly basal, the 2-3 stem 
leaf blades usually small and the uppermost one very reduced; sheaths glabrous, the 
basal ones breaking down into stiff fibers; ligule a ciliolate brown membrane, 0.3-1.0 mm. 
long; larger leaf blades 6-15 cm. long, 8-10 mm. wide, glabrous except for prominent 
silky marginal hairs at the base, a few scattered long hairs on the upper surface near the 
base. Peduncle slender, glabrous, exserted up to 20 cm.; inflorescence a solitary terminal 
panicle, densely silvery-silky, 6-15 cm. long, 1-2 cm. thick, cylindrical and little tapered; 
rachis, branches, and pedicels bearing elongated silky hairs; apex of pedicels dilated, 
disciform. Spikelets paired, equal, narrowly ovoid, 3.5-4.0 mm. long; callus truncate, 
bearing a ring of elongate silky white hairs up to 12 mm. long; first glume slightly shorter 
than the second, narrowly triangular, ciliolate at the tip, bearing elongated silky hairs on 
the back; nerves 3-5; second glume similar but 5-7-nerved; sterile lemma hyaline, nerve- 
less, triangular, the margins erose-jagged; fertile lemma similar, 0.5-1.1 mm. long; 
anther single, 1.8-2.8 mm. long, orange. 

Rare; Buenos Aires savanna; El Paraiso. An old Oersted specimen is 
stated to have come from Guanacaste, but bears no other locality data. 
February to April. Florida; West Indies; southern Mexico to Brazil. 

Imperata contracta (H.B.K.) Hitchc., Rep. Missouri Bot. Gard. 



276 FIELDIANA: BOTANY 

4:146. 1893. Saccharum contractum H.B.K., Nov. Gen. & Sp. 1:182. 
1816. Figure 100. 

Tall, coarse, erect perennial, 1-2 m. tall, forming large colonies by abundant scaly 
creeping rhizomes; culms unbranched, hollow, glabrous, 1-2 mm. thick; lower sheaths 
without blades; sheaths mostly overlapping, glabrous, with prominent auricles; ligule a 
firm brown ciliate membrane, 0.5-1.5 mm. long; blades up to 70 cm. long, 5-11 mm. wide, 
widest at the middle, tapering to a narrow base; midrib wide, white; blades scabrous on 
the margins, glabrous on the surfaces or occasionally with a few long papillose-based 
hairs on the auricles and behind the ligule; uppermost leaf blade much reduced. Inflores- 
cence a solitary terminal panicle, narrowly cylindrical, dense, 25-50 cm. long, tapering 
toward the apex, the numerous branches ascending, usually 5 cm. or less long; panicle 
densely silky because of the numerous long hairs of the branches and spikelets, white or 
purplish. Spikelets unequally pedicellate, the shorter pedicel of each pair ca. 0.5 mm. 
long, the longer ca. 1.5 mm.; rachis, branches, and pedicels scabrous and bearing scat- 
tered long silky hairs. Spikelets of each pair equal, narrowly ovoid, acute, 2.9-3.5 mm. 
long; callus truncate, bearing numerous silky hairs up to 12 mm. long; glumes nearly 
equal or the first slightly shorter, lanceolate or triangular, 3-nerved, sometimes scab- 
rous, their backs bearing scattered silky hairs, the tips sometimes minutely ciliolate; 
lower lemma sterile, a hyaline nerveless oblong scale 1.5-1.8 mm. long, its tip erose or 
lobed and bearing minute marginal spicules; fertile lemma similar, shorter, 0.7-1.1 mm. 
long; lodicules not seen; anther one, 1.6-2.0 mm. long; caryopsis ca. 0.7 mm. long, 
obovate-cylindrical, 2:1. Chromosome number n = 10 from Costa Rican material. 

Beaches and open areas, roadsides, near the Pacific Coast; Moin; 
Puriscal; San Jose area; mostly under 500 m. elevation. Blooming ap- 
parently yearlong. Southern Mexico to Peru and Brazil; West Indies. 

The plants are coarse and weedy, forming large colonies by 
rhizomatous spread; probably of little value for forage. Common name 
Zacate talquesa. 

ISACHNE R. Brown 

REFERENCE: A. S. Hitchcock, The North American species of 
Isachne. Contr. U.S. Natl. Herb. 22:115-122. PL 25-32. 1920. 

Inflorescence a panicle; spikelets biconvex, 2-flowered; glumes subequal, shorter than 
the florets, 5-7-nerved, a definite internode between the 2 glumes; florets similar or 
somewhat dimorphic, the second slightly shorter than the first, both containing flowers; 
lower flower staminate or perfect, the upper pistillate in our species; disarticulation 
above or below the glumes; florets joined by a very short rachilla segment and falling 
together. 

Although this genus is obviously panicoid in many features, the fact 
that both florets are well developed causes the spikelets to be more or 
less globose, rather than dorsally compressed as in most other panicoid 
genera. (Panicoideae: Paniceae.) 




FIG. 100. Imperata contracta. A, inflorescence; B, rhizomatous plant base; C, portion 
of an inflorescence branch with unequal pedicels. 



277 



278 FIELDIANA: BOTANY 

KEY TO SPECIES OF Isachne 

la. Low creeping plants; leaves cordate, 2-4 cm. long; upper floret puberulent 

I. polygonoides 

Ib. Tall erect or scrambling plants; leaves not cordate, 9-20 cm. long; both florets gla- 
brous I- o/rundinacea 

Isachne arundinacea (Swartz) Griseb., Fl. Brit. W. Ind. 553. 1864. 
Panicum arundinaceum Swartz, Prodr. Veg. Ind. Occ. 24. 1788. Fig- 
ure 101. 

Perennial from hard, knotty crowns; culms hard, woody, scrambling, in brush or 
reclining on steep slopes and rooting from lower nodes, much branched, up to 5 m. long; 
main culms hard and woody, 4-8 mm. thick, thick-walled, glabrous, resembling bamboo 
canes; branches much thinner; young canes bearing nearly bladeless sheaths which are 
deciduous at maturity; sheaths of main culms shorter than the internodes, those of 
smaller lateral branches overlapping; sheaths usually glabrous except for the ciliate 
overlapping margin, rarely papillose-hispid; prophylla prominent, 2-3 cm. long; ligule of 
stiff white hairs, 0.5-3.5 mm. long; blades scabrous, rarely appressed-hispid below or on 
both surfaces, 9-20 cm. long, 7-22 mm. wide, rather firm; inflorescences mostly born on 
leafy branches from the elongated main culms; peduncle glabrous, 4-11 cm. long; panicles 
dome-shaped, nearly as wide as long when fully expanded, 8-12 cm. long, 8-11 cm. wide, 
the branches spreading, much branched above the middle, the spikelets crowded at the 
periphery of the panicle; spikelets obovoid to subspherical, scarcely compressed, 1.4-1.8 
mm. long, disarticulating below the glumes, above the glumes, or the glumes dropping 
before the florets; glumes shorter than the spikelet, subequal, but the first somewhat 
narrower than the second, glabrous or with a few stiff hairs near the tips; first glume 
ovate, 5-nerved; 1.0-1.4 mm. long; second glume broadly ovate, 7-nerved, 1.0-1.7 mm. 
long; florets elliptical-obovoid, obscurely nerved; first floret 1.4-1.7 mm. long, the second 
1.0-1.3 mm. long, on a very short rachilla segment; anthers 2-3, ca. 1 mm. long, yellow to 
purple. Chromosome number n = 20 from Costa Rican material. 

Occasional; steep embankments, cliffs above streams, roadsides, 
forest margins; 30 to 1,900 m. elevation; more common on the Pacific 
slope, but also collected in the Limon area and at BriBri. Blooming 
yearlong. Southern Mexico to Peru; Caribbean Islands. 

Isachne polygonoides (Lam.) Doell in Mart., Fl. Bras. 2:273. 1877. 
Panicum polygonoides Lam. , Encycl. 4:742. 1798. Figure 102. 

Duration indefinite; total length of culms to 50-60 cm.; plants widely decumbent, the 
culms rooting at the lower nodes, the terminal portions erect; branching abundant; 
prophylla ca. 10 mm. long; culms hollow, soft, glabrous; nodes glabrous or papillose- 
pubescent; leaves numerous; sheaths shorter than the short internodes, papillose-ciliate 
on the overlapping margin, often papillose-hispid all over; ligule of rather sparse stiff 
hairs, 1-2.5 mm. long; leaf blades lanceolate, cordate-based, 2-4 cm. long, 7-13 mm. wide, 
thin, scabrous above and on the margins, papillose-ciliate at the base, sometimes to the 
tip, puberulent beneath; base of panicle included in the uppermost sheath; panicles 
terminal on leafy branches, 2-6 cm. long, pyramidal, the branches solitary, perpendicu- 
lar to the rachis; branches and pedicels bearing yellowish glandular bands; spikelets 
biconvex, on stiff spreading pedicels; spikelets 1.3-2.0 mm. long, disarticulating below or 
above the glumes, the 2 florets remaining together; a definite internode between the first 




FIG. 101. Isachne arundinacea. A, flowering culm; B, base of plant; C, cluster of 
spikelets. 

279 




FIG. 102. Isachne polygonoides. A, panicle; B, spikelet, showing dimorphic florets. 



280 



BURGER: FLORA COSTARICENSIS 281 

and second glumes, the first glume 1.2-1.8 mm. long, 5-nerved, broadly ovate; second 
glume 1.3-1.9 mm. long, 7-nerved, broadly ovate; glumes glabrous or with a few stiff 
papillose hairs near the tips; lower floret with a glabrous, chartaceous lemma and palea; 
lemma 1.5-1.7 mm. long, oval, convex, faintly 5-nerved, the palea subequal, the flower 
staminate; anthers 3, 0.4-0.5 mm. long, yellow; upper floret with lemma 1.2-1.5 mm. 
long, hemispherical, puberulent, stiff, the palea plane, its margins narrowly overlapped 
by the lemma; flower pistillate, its truncate lodicules bearing abundant bicellular hairs. 
Chromosome number n = 10 from Costa Rican material. 

Pond margins, ditches, swamps, often in shallow water; fairly com- 
mon in Guanacaste; Tuis; Volcan; 270-400 m. elevation. September to 
February; possibly yearlong. Guatemala and Honduras to Peru and 
northern Brazil; West Indies. 

ISCHAEMUM Linnaeus 

Annual or perennial grasses; inflorescence of 2-many digitate racemes or rames borne 
at the apex of a terminal peduncle; individual rame or raceme composed of many inter- 
nodes, each bearing 2 similar spikelets; disarticulation at the base of each internode, 
which falls with the 2 attached spikelets; one spikelet of each pair sessile or subsessile, 
the other pedicellate, the 2 similar, but the pedicellate one often somewhat smaller or 
reduced. First glume flattened, usually rigid and often cross-wrinkled below, thin and 
veiny above, its marginal flanges clasping the boat-shaped second glume of equal or 
slightly longer length; florets 2, concealed by the glumes; lower floret hyaline, awnless, 
with a staminate flower; upper floret shorter, the lemma hyaline, deeply bifid, the 
twisted awn arising at the juncture of the lobes; palea usually longer than the lemma. 
Pedicellate spikelet equal or smaller, often somewhat reduced and shorter-awned, in 
some species disarticulating from the pedicel. 

The genus is unusual in the Andropogoneae in having a well- 
developed, staminate lower floret. About 50 species, almost all native 
to the Old World, a few of these occurring as weeds in the American 
tropics. (Panicoideae: Andropogoneae.) 

KEY TO SPECIES OF Ischaemum 

la. Rames 2, closely appressed to each other, appearing as a single cylindrical spike; 
lower part of first glume of sessile spikelet strongly transversely corrugated 

/. rugosum 
Ib. Racemes 2-many, spreading apart; first glume of subsessile spikelet stiff but 

smooth, not corrugated 2 

2a. Racemes 3-many; nodes and leaf blades glabrous; blades 10-33 mm. wide 

/. latifolium 

2b. Racemes 2; nodes upwardly bearded; blades pubescent, less than 10 mm. 
wide /. indicum 

Ischaemum indicum (Houtt.) Merrill, J. Arnold Arbor. 19:320. 
1938. Phleum indicum Houtt., Nat. Hist. II: 13:198. t. 90, f. 2. 1782. 
Ischaemum ciliare Retz., Obs. Bot. 6:36. 1791. Figure 103. 




FIG. 103. Ischaemum species. /. latifolium: A, inflorescence; /. indicum: B, portion of 
a raceme; I. rugosum: C, spikelet pair and rachis internode. 



282 



BURGER: FLORA COSTARICENSIS 283 

Duration indefinite; plants sprawling, the lower parts of the culms long decumbent and 
rooting at the lower nodes; upper portions of culms ascending, branching freely; 
prophylla 2.5-6 cm. long; internodes ca. 1 mm. thick, hollow, glabrous; nodes wide, dark, 
upwardly bearded; sheaths keeled, papillose-pilose on the margin and on the surfaces, 
especially toward the apex; ligule a thin, brownish membrane, 0.5-1.0 mm. long; leaf 
blades flat, 4-9 cm. long, 4-8 mm. wide, papillose-pilose on the surfaces, with a few stout 
hispid hairs at the base. Peduncles slender, glabrous, exserted 5-15 cm.; inflorescence a 
conjugate pair of diverging racemes, 6-8 cm. long. Spikelets paired at each node of the 
disarticulating rachis, one subsessile, on a pedicel ca. 0.5 mm. long, the other on a 
pedicel ca. 3 mm. long; rachis internode and pedicel similar, triangular in cross section, 
stiffly ciliate on the external angles. Disarticulation at the base of the internodes, the 
spikelet pair falling together with the internode. Subsessile spikelet biconvex, ovate 3:1, 
tapering to a short, narrow base; first glume ca. 4 mm. long, its basal third stiff, yellow, 
smooth, very broad, its marginal flanges covering the base of the second glume; upper 
two-thirds of the first glume thin, with many green nerves, most of them paired; apex 
bidentate; surface with numerous stiff spreading hairs; second glume longer than the 
first, bulging near the base, slightly winged near the tip, 5-nerved, tapering into a short 
straight awn; lower lemma ovate, acute, hyaline, ca. 3.5 mm. long, with a similar palea of 
about equal length; lodicules 2, truncate; stamens 3, the anthers yellow, 1.6-2.2 mm. 
long; pistil absent; upper floret perfect-flowered; lemma thin, hyaline, apex bifid to the 
middle, the awn arising between the teeth; basal segment of awn brown, tightly twisted, 
3-4 mm. long; upper segment thin, only slightly twisted, purple, 6-7 mm. long; palea 
thin, hyaline, acute, longer than the lemma; lodicules 2, truncate; stamens 3, the anthers 
similar to those of the lower floret but longer; pistil with 2 separate naked style 
branches; stigmas purple. Pedicellate spikelet: Similar to the subsessile one, but usually 
smaller, the flower sometimes abortive. Chromosome number n = 9. 

The only Costa Rican collection is the following: Puntarenas, Golfito; 
very common on sand along a stream, elevation 2m., 11 December 
1968, P. & D. 11571. Introduced from the Old World; reported from 
Panama and Guyana. 

Ischaemum latifolium (Spreng.) Kunth, Rev. Gram. 1:168. 1829. 
Andropogon latifolius Spreng., Syst. Veg. 1:286. 1825. Figure 103. 

Perennial; plants sprawling or erect, the culms 45-150 cm. long, sometimes rooting at 
the decumbent lower nodes, freely branching; internodes solid, pithy, glabrous; nodes 
wide, glabrous; sheaths glabrous except for the bearded collar, keeled toward the apex; 
ligule a brown membrane, 0.5-2.0 mm. long, tipped with cilia 0.5-2.0 mm. long; leaf 
blades flat, broad, 6-10 x longer than wide, 6-24 cm. long, 10-33 mm. wide, narrowed 
abruptly to the base, bearded on the collar and lower side at the base, otherwise gla- 
brous. Peduncle slender, glabrous, exserted 3-10 cm.; uppermost leaf blade reduced; 
peduncle forking once or twice at the tip, the branches bearing a fan-shaped cluster of 
5-17 racemes, each 6-12 cm. long. Spikelets paired, one subsessile, its pedicel ca. 0.3 mm. 
long, the other on a pedicel ca. 3 mm. long; rachis internodes and pedicels bearded on the 
angles and at the tip; disarticulation at the base of the internodes, the spikelet pair 
falling; sometimes the pedicellate spikelet disarticulates from its pedicel. Subsessile 
spikelet: 4.5-7.0 mm. long; first glume narrowly ovate, 4.5:1, acute, flat to convex on the 
back; margins slightly keeled and ciliate near the bifid tip; basal portion firm, smooth; 
upper portion herbaceous, 5-7-nerved, some of the nerves forking; second glume convex, 



284 FIELDIANA: BOTANY 

awn-tipped, slightly longer than the first; lower lemma nearly as long as the first glume, 
4.0-5.5 mm. long, hyaline, acute, ciliate above, its palea slightly shorter; lodicules 2, 
truncate; anthers 3; upper floret with a hyaline, bifid lemma 3.5-4.0 mm. long, bearing an 
awn 5.0-9.5 mm. long from the sinus; palea about as long as the lemma; lodicules 2, 
truncate; anthers 3, yellow, 2.1-2.3 mm. long; caryopsis 1.5 mm. long, clear amber, with 
a large embryo. Pedicellate spikelet: Similar to the subsessile one, but becoming later- 
ally compressed by the folding of the first glume along one keel, the other scarcely 
developed; florets similar to those of the subsessile spikelet, but somewhat red-iced and 
the fertile lemma shorter-awned. 

Brushy roadside, Canton de Dota, 1,400-1,800 m.; Buenos Aires; 
stream banks, northern Guanacaste. September to February. Mexico 
to Ecuador and Brazil. Chromosome number n = 18 from a Costa 
Rican specimen (P. & D. 11067) that is smaller and has narrower 
blades than most specimens of this species. 

Ischaemum rugosum Salisb., Icon. Stirp. Rar. 1, pi. 1. 1791. Fig- 
ure 103. 

Caespitose annual; culms 55-130 cm. tall, erect or the bases decumbent and rooting; 
branching freely from most nodes; prophylla prominent, 4-8 cm. long, with several 
accessory nerves on each lateral flange; culms 2-3 mm. thick, hollow, glabrous; nodes 
wide, dark, bearded at the lower margin with a circle of appressed, ascending, silky, 
white hairs; sheaths shorter than the internodes, glabrous except on the margin below 
the apex, slightly keeled above; ligule a thin brown membrane, 2.0-5.5 mm. long, adnate 
to the erect sheath auricles; leaf blades flat, 8-20 cm. long, 7-15 mm. wide, softly 
papillose-pilose on both surfaces; base of blade usually contracted into a short, woolly 
pseudopetiole. Peduncle glabrous, erect, exserted 3-11 cm.; inflorescences several, 
borne on the culm apex and from the upper leaf axils, consisting of a pair of conjugate 
rames, closely appressed to each other and appearing as single cylindrical spike ca. 5 
mm. in diameter, 3-10 cm. long, the 2 rames at maturity somewhat spreading apart near 
the apex. Spikelets paired, one sessile and one pedicellate at each node; rachis inter- 
nodes thick, 2.8-3.5 mm. long, triangular in cross section, the external faces yellowish, 
rigid, the inner side hyaline, thin, the interior hollow; external angle of the surface with 
a Line of stiff appressed hairs; base of the internode and callus of the sessile spikelet 
bearded with short ascending hairs; pedicel similar to the rachis internode, usually 
shorter, 1.5-2.5 mm. long; rames disarticulating freely at the base of each internode, the 
rachis internode, pedicel, and the 2 spikelets falling as a unit. Sessile spikelet: First 
glume 3.8-5.0 mm. long, ovate, acute, 2.5:1, slightly convex, the lower three-fifths rigid, 
yellowish, very strongly transversely corrugated, the upper two-fifths flat, herbaceous, 
longitudinally striate with many fine green nerves; margins of the glume bearing 2 
inflexed flanges that clasp the margins of the second glume; second glume keeled, boat- 
shaped, slightly longer than the first, acute; lower lemma thin, ovate, acute, faintly 
nerved, awnless, its palea a hyaline nerveless scale, shorter than the lemma; stamens 3, 
the anthers 1.5-1.8 mm. long, pink; pistil rarely present; upper floret perfect-flowered or 
pistillate, its lemma hyaline, 3-4 mm. long, bifid to the middle, the awn attached on the 
outer side at the junction of the acuminate teeth; awn 1.5-2.0 cm. long, bent, the basal 
half brown, strongly twisted, the upper segment thin, white, loosely twisted; palea 
hyaline, nerveless, shorter than the lemma. Pedicellate spikelet: Similar to the sessile 



BURGER: FLORA COSTARICENSIS 285 

spikelet but smaller, the first glume asymmetric, ovate 2:1, the lower half yellow, rigid, 
sometimes slightly undulate, the upper portion green, herbaceous, finely striate; flower 
usually staminate. Chromosome number n = 9 from Costa Rican specimens. A base 
number of x = 10 is also reported for this genus. 

Occasional but locally abundant; Curatella-Byrsonima savannas in 
northern Guanacaste, in road ditches, pastures, sometimes in shallow 
water; sea level to 600 m. elevation; also collected at Los Angeles (Rio 
Penas Blancas), Chomes, and Turrialba. This Old World species is 
apparently a recent introduction in Costa Rica, the earliest collection 
dating to 1950. Panama, Venezuela, Trinidad, Cuba, and Jamaica. 

IXOPHORUS Schlechtendal 

Caespitose perennial; inflorescence a panicle with simple spreading or ascending 
branches racemosely arranged along the rachis; spikelets subsessile in 2 rows along the 
lower sides of the triquetrous branches; each spikelet subtended by a single bristle 
longer than the spikelet; disarticulation below the glumes. Spikelets dorsally com- 
pressed; first glume much shorter than the spikelet, 3-nerved; second glume and sterile 
lemma subequal, as long as the spikelet and concealing the fertile floret; second glume 
many-nerved; lower lemma 5-nerved, containing 3 stamens; palea 2-keeled, as long as 
the lemma or slightly longer, at full maturity of the fruit becoming circular with a 
cordate base and broad chartaceous wings, much wider than the remainder of the 
spikelet; upper floret shorter than the spikelet, elliptical, the lemma indurate, apiculate, 
with margins inrolled over the edges of the indurate palea; flower of upper floret pistil- 
late, rarely with rudimentary stamens. 

Ixophorus is similar to Setaria in possessing sterile branches (bris- 
tles) in the inflorescence, but differs in the winged spikelets. 
(Panicoideae: Paniceae.) 

Ixophorus unisetus (Presl) Schlecht., Linnaea 31:421. 1861-62. 
Urochloa uniseta Presl, Rel. Haenk. 1:319. 1830. Figure 104. 

Coarse caespitose perennial; culms 50-140 cm. tall, up to 1 cm. thick, rather succulent, 
erect, unbranched; sheaths mostly overlapping, somewhat keeled, glabrous; nodes 
glabrous or slightly appressed-pubescent; ligule a lacerate or ciliate membrane, 1.0-2.5 
mm. long; blades lax, with a conspicuous white midrib, glabrous, 10-25 mm. wide, up to 
75 cm. long; panicles 10-25 cm. long, ovoid-cylindrical, of numerous racemosely arranged 
simple racemes, the lower ones 2-8 cm. long, the upper successively shorter, often naked 
near the base; spikelets dorsally compressed, 3.5-4.7 mm. long, each subtended by a 
scabrid purple bristle (sterile branch), 1-2 x as long as the spikelet; outline of young 
spikelets lanceolate; first glume broadly ovate, acute, 3-nerved, 0.7-1.5 mm. long; second 
glume many-nerved; lower lemma 5-nerved; palea of lower lemma at maturity becoming 
circular, with a cordate-auriculate base, expanding the spikelet to circular outline; sta- 
mens 3, 2-3 mm. long; upper lemma indurate, papillose, brownish. Chromosome number 
approximately n = 31-33 from Costa Rican material. Other counts of n = 17 are known. 

Sea level to 1,200 m. elevation; common in Guanacaste, San Jose 
area, Limon area, Turrialba, Siquirres, Palmar Norte. Mexico to 




FIG. 104. Ixophorus unisetus. A, panicle; B, young spikelet; C, mature spikelet with 
winged palea of the lower floret; D, mature spikelet from second glume side, showing 
winged palea of lower floret; E, winged palea of lower floret, F, upper (pistillate) floret. 



286 



BURGER: FLORA COSTARICENSIS 287 

Costa Rica; Colombia and Venezuela; Cuba. This species is used for 
forage production under the names Zacate de Honduras and Zacate 
bianco. 

JOUVEA Fournier 

Stoloniferous, pungent-leaved perennial maritime grasses of coastal dunes and mud 
flats; dioecious, the staminate and pistillate inflorescences very different. Staminate 
plants: Inflorescences clustered from upper few leaf axils, 1-3 peduncles arising in each 
axil, forming a cylindrical or flabellate group; individual inflorescence a spike on a slen- 
der, short-exserted peduncle. Spikelets sessile, many-flowered; first glume absent or a 
minute scale; second glume 1-nerved, shorter than the first floret; lemmas faintly 3- 
nerved; palea nearly as long as the lemma, 2-keeled; rachilla not disarticulating; anthers 
3; lodicules 2, truncate, vasculated. Pistillate plants: Pistillate inflorescence a cluster of 
stiff, sharp-pointed hornlike bodies, subtended closely by foliage leaves, the horns in- 
terspersed with prominent prophylls; individual horns falcate, cylindrical, hard, 
acerose-pointed, containing several pistils in alternating succession, each sealed within a 
linear cavity in the spongy interior of the horn, the style emerging through a small apical 
ostiole; caryopsis linear, naked within the cavity or accompanied by a small nerveless 
scale. 

The horns have been interpreted as spikelets by Weatherwax (Bull. 
Torrey Club 66:315-325. 1939), but their structure and their aggrega- 
tion into prophyllate clusters are so unusual as to make the homology 
dubious. 

Jouvea is a genus of only two species, ranging from Baja California 
to Panama. Because of the highly unusual structures of the female 
inflorescences, the relationship of the genus to others is obscure. Leaf 
anatomy and chromosome size and number indicate that it is 
Chloridoid. (Chloridoideae: Aeluropodeae.) 

KEY TO SPECIES OF Jouvea 

la. Plants of sand dunes on open beaches, forming dense, leafy mounds; stolons thick 
and stiff (often becoming buried in the sand), usually with an erect branch at each 
node; their internodes usually 2-6 cm. long, leaf sheaths covering one-third or more 
of their length; leaf blades persistent J. pilosa 

Ib. Plants of saline mud flats behind the beaches or in estuaries, forming sparse flat 
mats on surface of soil; stolons thin and wiry, not becoming buried; their internodes 
usually 6-10 cm. long, leaf sheaths usually less than one-third as long as internodes, 
the leaf blades usually deciduous from the sheath J. straminea 

Jouvea pilosa (Presl) Scribn., Bull. Torrey Bot. Club 23:143. 1896. 
Brizopyrum pilosum Presl, Rel. Haenk. 1:280. 1830. 

Plants forming mats or mounds on sandy beaches; strongly Stoloniferous, the stolons 
often buried in sand, profusely branching; flowering on branches or raised tips of the 
stolons; culms hollow, glabrous, strongly ridged; nodes yellowish, smooth; leaf sheaths 
keeled, shorter or longer than the internodes, 1-3 cm. long, glabrous except for a cluster 




FIG. 105. Jouvea straminea. A, staminate plant with inflorescence; B, pistillate 
inflorescence; C, pistillate horn with emergent stigmas. 



288 



BURGER: FLORA COSTARICENSIS 289 

of tuberculate-based auricular hairs; prophylls prominent, 2-keeled, up to 2 cm. long; 
ligules membranous, crowned with a dense fringe of white cilia, less than 1 mm. long; 
leaf blades stiff, often folded, 5-15 cm. long, or much shorter in the female inflorescence, 
2-4 mm. wide, glabrous beneath, with scattered long hairs above, the upper surface 
strongly ridged. Staminate inflorescence: Spikes 1-several, terminal and axillary from 
upper sheaths; peduncle included or slightly exserted; groups of spikes forming a cylin- 
drical cluster; individual spikes 5-7 cm. long, oblong, the spikelets borne alternately in 2 
rows on 2 sides of a triquetrous rachis. Spikelets overlapping, often proliferous and with 
up to 30 florets, 1.5-4.0 cm. long; first glume absent or a minute scale less than 1 mm. 
long; second glume 3.5-4.0 mm. long, 1-nerved, keeled, lance-linear; rachilla persistent, 
the florets not disarticulating; lemmas with prominent midrib and several faint lateral 
nerves, ovate, keeled, 3.5-4.5 mm. long, acute, glabrous; palea as long as or slightly 
longer than the lemma, prominent, scabrid on the keels; anthers 3, 2.5 mm. long, 
purplish; lodicules 2, truncate, lacerate, vasculated. Spikelets continue to produce new 
florets at the tip after flowering has ceased in the lower ones. Pistillate inflorescence: a 
dense, flabellate cluster of stiff, sharp-pointed hornlike bodies, these subtended by 
short, stiff leaf blades and interspersed with prominent prophylls; individual horns fal- 
cate, cylindrical, 2-4 cm. long, acerose-pointed, containing usually 2-5 caryopses, each 
sealed within a cylindrical cavity in the spongy interior of the horn, the style emerging 
through a small apical ostiole; caryopsis linear, tan, filling the cavity of the horn, naked 
or rarely accompanied by a small nerveless bract. Chromosome number n = 10 from 
Costa Rican material. 

Pacific beaches of Guanacaste, on low sand dunes; Playa Tamarindo, 
Playa Naranjo in Parque Nacional de Santa Rosa, Puerto Soley. Prob- 
ably blooming yearlong. Pacific beaches; Mexico, Guatemala, El Sal- 
vador, Honduras, and Costa Rica. 

Jouvea straminea Fourn., Bull. Soc. Roy. Bot. Belgique 15:475. 
1876. Figure 105. 

Plants caespitose in dense, hard tufts; the culms arising from prophyllate bases, 
reclining, forming extensive flat open mats on dry mud flats; stolons numerous, thin and 
wiry, sparsely branched, up to 150 cm. long; culms arising in small clumps from the 
stolons, glabrous, the nodes dark-colored; leaf sheaths 0.5-2.0 cm. long, usually less than 
one-third as long as the internodes, glabrous except at the auricles, not keeled; ligules 
0.5-1.0 mm. long, dilate; leaf blades 1.5-5.0 cm. long, 2-3 mm. wide, often folded, tending 
to disarticulate from the sheaths on stolons. Staminate inflorescence: A cluster of several 
terminal or axillary spikes from the apex of the culms and the upper nodes, the pedun- 
cles mostly included; individual spikes 2-4 cm. long, slender. Staminate spikelets usually 
2-4, appressed along 2 sides of a thin triquetrous rachis, strongly laterally compressed 
and keeled, 1-4 cm. long, proliferous, the rachilla producing new florets at the tip after 
the lower ones have shed their pollen; first glume usually absent or up to 5 mm. long and 
1-nerved, acicular, second glume lance-linear, 1-nerved, sometimes with an additional 
weak lateral nerve, 4-6 mm. long, stiff, scabrid on the keel; florets up to 30, not disar- 
ticulating; lemmas 3.5-4.0 mm. long, narrowly ovate, acute, glabrous, 3-nerved, rarely 
with additional faint nerves, awnless; palea about as long as the lemma, scabrid-ciliate on 
the keels; flower staminate; stamens 3, the anthers ca. 2.5 mm. long, yellowish or 
purplish; lodicules 2, truncate, fleshy, prominently vasculated. Pistillate inflorescence: 
Plants bearing at the upper several nodes of the culms axillary and terminal clusters of 



290 FIELDIANA: BOTANY 

several rigid hornlike cylindrical bodies, their bases concealed by the subtending leaf 
sheath and several papery prophylls; horns 1.5-3.0 cm. long, ca. 1.5 mm. thick, curved, 
rigid, tapering to a pointed base and apex, readily disarticulating at the base; pistillate 
flowers 2-3, concealed within the horn by an adnate narrowly triangular flap of tissue, 
the single flattened style emerging through a small apical ostiole; stigmas 2, not strongly 
plumose; ovary naked or accompanied by a narrow hyaline bract. Chromosome number 
n = 10 from Costa Rican material. 

Drying mud flats behind beaches and in estuaries, Pacific Coast of 
Guanacaste, Puerto Castillo, Puerto Soley, Playa Naranjo in Parque 
Nacional de Santa Rosa. Blooming sparsely in December and January; 
staminate plants only seen in Costa Rica. Mexico to Panama, on the 
Pacific beaches. 

LASIACIS (Grisebach) Hitchcock 

REFERENCE: G. Davidse, A systematic study of the genus Lasiacis 
(Gramineae: Panicoideae), Unpubl. Ph.D. Diss., Iowa State Univ. Li- 
brary. 231 pp. 1972. 

Perennial, erect, scandent, or prostrate grasses; caespitose or creeping; culms much- 
branched, often thick and semi- woody; internodes solid or hollow; ligules membrana- 
ceous; leaf blades linear to ovate, sometimes borne on a short pseudopetiole. Inflorescence 
an open or contracted panicle, terminal on the culm or on leafy branches. Spikelets 
subglobose to globose, ovate, or elliptic, placed obliquely on the pedicel, disarticulating 
entire; glumes and lower (sterile) lemma broad, abruptly apiculate, many-nerved, mem- 
branaceous, but becoming black and shiny at maturity, woolly at the apex; first glume 
one- to two-thirds as long as the spikelet, 5-13-nerved, its lower margins overlapping; 
second glume and sterile lemma subequal, ca. as long as the spikelet, 7-15-nerved; lower 
(sterile) lemma enclosing a palea one-fourth as long to equalling the lemma; staminate 
flower present or absent; fertile lemma hard, rigid, obtuse, its margins inrolled and 
enclosing the edges of a similar palea; floret usually dark brown when mature, broadly 
elliptic to obovate; palea convex above, concave near the base; both lemma and palea 
with a tuft of wool at the tip; stamens 3; styles 2, separate; lodicules 2, fleshy, truncate, 
vasculated. 

Lasiacis is a genus of 16 species of grasses native to tropical and 
subtropical parts of North and South America and the West Indies. 
The plants are distinguished from all other panicoid grasses by their 
rotund black spikelets, set obliquely on the pedicel and woolly-tufted 
at the tip. Individuals of most of the species are large, somewhat 
woody plants, vaguely resembling small bamboos or Olyra latifolia. 
They are abundant in somewhat disturbed sites on roadsides, in brush, 
or on the margins of forests. Recent studies by Davidse have shown 
that the mature, black spikelets store oil droplets in the inner linings of 
the bracts. They are consumed by fruit-eating birds, who obtain nutri- 
tion from this oil, rather than from the heavily protected and undi- 



BURGER: FLORA COSTARICENSIS 291 

gested grain. This peculiarity of the spikelets, which immediately sets 
the genus off from all other grasses, undoubtedly accounts for the 
abundance of the plants on the forest margins where birds frequently 
perch. The genus is most closely related to Acroceras. (Panicoideae: 
Paniceae.) It is commonly called carrizo. 

KEY TO SPECIES OF Lasiacis 

la. Culms solid, pithy; plants sprawling or creeping and rooting at lower nodes . . 2 
Ib. Culms hollow or mostly so; plants creeping, ascending, or clambering on brush or 

trees 5 

2a. Ligules 1.4 mm. or less long 4 

2b. Ligules 2.0-6.0 mm. long; leaf blades linear-lanceolate, 13-29 cm. long ... 3 
3a. Sheaths glabrous; spikelets paired or clustered near ends of panicle branches; 

lower floret staminate, with long palea L. oaxacensis var. oaxacensis 

3b. Sheaths puberulent or pubescent; spikelets solitary on long pedicels; lower floret 

sterile, its palea two-thirds or less as long as lemma L. linearis 

4a. Foliage glabrous; blades 16-25 cm. long; lower floret staminate 

L. oaxacensis var. maxonii 
4b. Foliage pubescent; blades 8-17 cm. long; lower floret sterile 

L. rhizophora 

5a. Plants creeping and rooting at the lower nodes; ligules 4.5-9.0 mm. long; palea of 

lower floret less than half as long as lemma L. standleyi 

5b. Plants erect or scrambling; culms hollow 6 

6a. Leaf blades conspicuously cordate-based, clasping stem, 14-42 cm. long; lower 
nodes decumbent, producing conspicuous thick wiry prop roots; panicles very 

large, 20-120 cm. long, very open and dome-shaped L. procerrima 

6b. Blades not conspicuously cordate-based, smaller; plants without prop roots; 

panicles less than 30 cm. long, mostly compactly flowered 7 

7a. Ligules of upper leaves readily visible, usually 2-7 mm. long 8 

7b. Ligules of upper leaves not readily visible, usually less than 1.5 mm. long 9 

8a. Ligules mostly 4-6 mm. long; panicle spherical, less than 9 cm. long; upper 

leaf surface scabrous L. scabrior 

8b. Ligules mostly less than 3.5 mm. long; panicles large, ovoid, 9-30 cm. long; 
upper surfaces of blades glabrous or pubescent 

L. sorghoidea var. sorghoidea 

9a. Leaf blades glabrous on both surfaces 10 

9b. Leaf blades with some pubescence on at least one surface 14 

lOa. Blades linear to narrowly lanceolate, 7-11 x longer than wide, usually less 

than 2 cm. wide 11 

lOb. Leaf blades broadly lanceolate to ovate, 3-6 x longer than wide, more than 2 

cm. wide 13 

lla. Panicles few-flowered, branches spreading or reflexed; mature pedicels sharply 

divergent; culms zigzag L. divaricata var. divaricata 

lib. Panicle branches not reflexed; culms straight or zigzag 12 

1 -a. Base of panicle included in uppermost sheath; pedicels and branches short 

L. divaricata, var. leptostachya 



292 FIELDIANA: BOTANY 

12b. Base of panicle usually exserted; pedicels slender, widely spreading, 
flexuous L. nigra 

13a. Main inflorescence branches sparsely branched, bearing few spikelets; pedicels 
appressed, short; blades with short, puberulent pseudopetioles L. sloanei 

13b. Main inflorescence branches much branched; pedicels not appressed; leaf blades 

lacking a distinct pseudopetiole L. ruscifolia var. ruscifolia 

14a. Leaf blades lanceolate, 6-11 x longer than wide 15 

14b. Leaf blades ovate, 3-6 x longer than wide 16 

15a. Panicles 5-12 cm. long; pedicels spreading; spikelets 4.0-5.0 mm. long . L. nigra 

15b. Panicles 9-25 cm. long; pedicels not spreading; spikelets 3.4-4.1 mm. long 

L. sorghoidea var. sorghoidea 

16a. Blades 6-14 cm. long, 18-44 mm. wide L. ruscifolia var. ruscifolia 

16b. Blades 4-7 cm. long, 8-15 mm. wide L. rugelii var. pohlii 

Lasiacis divaricata (L.) Hitchc., Contr. U.S. Natl. Herb. 15:16. 
1910, var. divaricata. Panicum divaricatum L., Syst. Nat. ed. 10. 
2:871. 1759. 

Robust perennial; caespitose; culms erect or arching and clambering in brush, up to 7 
m. long, the upper portions of the culms and main branches usually zigzag; internodes 
hollow, 5-9 mm. thick, glabrous or puberulent; nodes glabrous; sheaths glabrous or 
puberulent, ciliate on the margin; auricular hairs up to 3 mm. long; ligule inconspicuous, 
usually less than 0.6 mm. long, ciliolate or glabrous; leaf blades usually 5-12 cm. long, 
6-14 mm. wide, linear or narrowly lanceolate, glabrous, scabrous, or puberulent. 
Inflorescence usually 2-12 cm. long, the longest branch 2-8 cm. long; branches spreading 
or reflexed; pedicels strongly divergent. Spikelets obovate, 3.5-4.5 mm. long; first glume 
1.2-2.5 mm. long, 7-11-nerved; second glume 9-11-nerved; lower (sterile) lemma lacking 
a flower, 9-13-nerved, its palea half or more as long; upper (fertile) lemma 3.4-4.0 mm. 
long, whitish to brown; anthers white, ca. 2 mm. long; stigmas purple; caryopsis 2.2-2.4 
mm. long, whitish. Chromosome number n = 18. 

Caribbean lowlands, in brushy margins of forests. Southern Florida; 
West Indies and northern South America; Mexico to Panama. Usually 
fruiting from June to March. 

Var. leptostachya (Hitchc.) Davidse, Ann. Missouri Bot. Gard. 
64:375. 1977. Lasiacis leptostachya Hitchc., Contr. U.S. Natl. Herb. 
22:19. 1920. 

This variety differs from the typical var. divaricata in its narrower leaf blades, occa- 
sionally heavily pubescent culm internodes, somewhat larger spikelets, and smaller, 
denser panicles which are included at the base and lacking divaricate branches except at 
full maturity. 

Northwestern Costa Rica. Oaxaca and Veracruz to Panama. 

Lasiacis linearis Swallen, Phytologia 4:427. 1953. 

Creeping perennial; the culms solid, 2-5 mm. thick, the lower nodes decumbent and 
rooting, the terminal portions erect, up to 100 cm. long, freely branching, forming large 
tangled colonies; internodes glabrous or with a line of pubescence; nodes glabrous; 



BURGER: FLORA COSTARICENSIS 293 

sheaths puberulent or pubescent, the overlapping margin ciliate; ligules tan to dark 
brown, ciliate, 1.4-4.8 mm. long, conspicuous; leaf blades linear, asymmetric at the base, 
13-22 cm. long, 8-18 mm. wide, glabrous, scabrid, or puberulent. Inflorescence 19-30 cm. 
long, the branches spreading, up to 23 cm. long, naked on the lower half, the long- 
pedicellate spikelets borne toward the tips. Spikelets narrow, obovate, 3.9-4.5 mm. long; 
first glume 2.0-2.5 mm. long, 7-9-nerved; second glume 8-11-nerved; lower (sterile) 
lemma empty, 9-11-nerved, its palea one- to two-thirds as long as the lemma or rarely 
absent; upper (fertile) lemma 3.9-4.1 mm. long; anthers white; stigmas purple; caryopsis 
2.2-2.4 mm. long. Chromosome number n = 18. 

Cloud forests, oak and pine forests, forest margins, elevation 1,400- 
2,400 m. San Gabriel. June through March. Southern Mexico to North- 
ern Panama. 

Lasiacis nigra Davidse, Phytologia 29:152. 1974. Figure 106. 

Caespitose perennial; culms erect at the base, arching above and clambering into 
vegetation, up to 12 m. long; internodes hollow, up to 10 mm. thick, glabrous to densely 
papillose-pubescent; nodes glabrous; sheaths glabrous to pilose, the margin ciliate with 
hairs to 3 mm. long; auricular hairs to 4 mm. long; ligule 0.5-2.0 mm. long, glabrous to 
ciliate; leaf blades linear to lanceolate, 5-15 cm. long, 6-26 mm. wide, glabrous or com- 
monly pilose. Panicle usually 5-12 cm. long, the longest branch to 8 cm. long; spikelets 
few, long-pedicellate; panicle branches ascending to diverging, glabrous to pilose. 
Spikelets obovate, 3.6-5.5 mm. long; first glume 1.6-3.2 mm. long, 5-13-nerved; second 
glume 7-13-nerved; lower (sterile) lemma 9-11-nerved, its palea half as long as the lemma 
or longer; flower absent or staminate with anthers rudimentary or up to 2.7 mm. long, 
white; stigmas white; caryopsis 2.4-2.7 mm. long, light brown. Chromosome number n = 
18. 

Forest margins, thickets, and brush; elevations 900-2,300 m. This 
species is common in Costa Rica, mostly on the Pacific slope. It is not 
known from the lower and dryer parts of Guanacaste. Flowering most 
commonly from June to January. Central Mexico to northwestern 
South America (Colombia, Venezuela, and Ecuador). 

This species has usually been included in L. sorghoidea until re- 
cently, but differs in the delicate, open panicle with few spikelets. 

Lasiacis oaxacensis (Steud.) Hitchc., Proc. Biol. Soc. Wash. 24:45. 
1911, var. oaxacensis. Panicum oaxacense Steud., Syn. PL Glum. 
1:73. 1854. 

Perennial; culms extensively creeping and rooting at the nodes, 0.5-2.0 m. long, much 
branched, the terminal portions more or less ascending; internodes 2-5 mm. thick, usu- 
ally solid, glabrous; nodes glabrous; sheaths glabrous or rarely somewhat puberulent 
when young; margins usually ciliate; ligule prominent, 2-6 mm. long (see also var. 
maxonii with short ligules), brown, often puberulent or hispid on the back, the edges 
ciliate or glabrous; leaf blades 13-29 cm. long, 12-24 mm. wide, narrowly linear- 
lanceolate, glabrous, usually scabrous on edges and midrib, rarely puberulent when 
young. Inflorescence mostly terminal, 16-31 cm. long, the longest branch 4-24 cm. long; 
branches widely spreading, mostly naked on lower two-thirds; spikelets pedicellate in 




FIG. 106. Lasiacis nigra. A, culm segment; B, base of plant; C, inflorescence; D, 
spikelet. 



294 



BURGER: FLORA COSTARICENSIS 295 

pairs or small clusters toward the ends of the branches. Spikelets 3.8-4.2 mm. long; first 
glume 1.6-2.3 mm. long, 4-9-nerved; second glume 7-11-nerved; lower lemma with an 
equal palea and a staminate flower with well-developed lodicules; anthers 1.0-2.3 mm. 
long, sometimes rudimentary; upper (fertile) lemma 3.2-3.6 mm. long; anthers 1.7-2.3 
mm. long; stigmas purple; caryopsis 2.0 mm. long. Chromosome number n = 18. 

Forest margins and openings, roadsides, sometimes in cafetales, 
mostly on the Pacific slope. This species is more weedy than most of 
the others of the genus, and may form sizable patches in disturbed 
sites. Mostly blooming from November to April. Southern Mexico to 
Peru, Ecuador, Venezuela, and Colombia; Greater Antilles. 

Var. maxonii (Swallen) Davidse, Ann. Missouri Bot. Gard. 64:375. 
1977. L. maxonii Swallen, loc. cit. 30:231. 1943. 

This variety differs in having short ligules, 1.5 mm. or less long. 

Costa Rica and Panama; Honduras. 

Lasiacis procerrima (Hack.) Hitchc., Proc. Biol. Soc. Wash. 24:145. 
1911. Panicum procerrimum Hack., Oesterr. Bot. Z. 51:431. 1901. 
Figure 107. 

Short-lived perennial or annual; culms decumbent at the base and producing conspicu- 
ous unbranched prop roots from lower nodes; culms in clumps, 0.5-5 m. long, simple or 
sparingly branched, 4-12 mm. thick; internodes hollow, glabrous or rarely puberulent 
below the glabrous nodes; sheaths glabrous or puberulent, glaucous; ligule 0.5-1.5 mm. 
long; leaf blades 14-42 cm. long, 14-57 mm. wide, the base cordate and clasping the stem, 
ciliate; surfaces glabrous to velutinous, rarely hispid, glaucous beneath. Inflorescence a 
large, very open panicle, 20-120 cm. long, about as wide; spikelets mostly borne toward 
the ends of the branches. Spikelets 3.0-4.8 mm. long; first glume 1.4-3.0 mm. long, 
7-11-nerved; second glume 9-11-nerved; lower (sterile) lemma 9-11-nerved, usually en- 
closing a palea at least three-fourths as long; flower usually staminate, rarely perfect; 
anthers 1.8 mm. long, rarely rudimentary; upper (fertile) lemma 3.1-3.4 mm. long, 
1.8-2.1 mm. wide; lemma black to grayish brown at maturity, its upper margins not 
inrolled; anthers 1.6-1.9 mm. long; stigmas white; caryopsis 2.3 mm. long, dark brown. 
Chromosome number n = 18 from Costa Rican specimens. 

Common on exposed road embankments and brushy open slopes, up 
to 1,800 m. elevation, most common on the Pacific Slope. Blooming 
from June to January. Mexico to Northern South America, from Peru 
to Guyana. Common names: Alajuela, Cariuela. 

Lasiacis rhizophora (Fourn.) Hitchc. Proc. Biol. Soc. Wash. 24:145. 
1911. Panicum rhizophorum Fourn., Mex. PI. 2:31. 1881. 

Perennial; culms creeping, rooting at the nodes, freely branching; upper parts of culms 
erect to 1 m. tall; culms slender, 2-3 mm. thick, solid; internodes puberulent toward the 
apex; nodes glabrous or puberulent; sheaths shorter than the internodes, puberulent, 
hirsute, or papillose- hispid, the overlapping margin ciliate above; auricular hairs of 
sheath apex prominent; ligule a ciliate membrane, 0.4-1.1 mm. long, tipped with hairs 




FIG. 107. Lasiacis procerrima. A, culm base with prop roots; B, leaf blade with 
cordate base; C, portion of inflorescence; D, spikelet; E, two views of an upper (fertile) 
floret. 



296 



BURGER: FLORA COSTARICENSIS 297 

1.5-3.5 mm. long; leaf blades lanceolate, 8-17 cm. long, 16-37 mm. wide; surfaces hispid, 
puberulent, scabrous or glabrous; base asymmetrical, one side cordate-clasping. 
Inflorescence 10-24 cm. long, the longest branch up to 11 cm. long; branches ascending or 
spreading, scabrous or puberulent; spikelets clustered in pairs or small groups toward 
the tips of the branches. Spikelets 3.1-4.0 mm. long; first glume 1.4-2.1 mm. long, 
5-7-nerved, second glume 7-9-nerved; lower (sterile) floret lacking a flower or rarely with 
rudimentary stamens, the lemma 7-9-nerved, its palea three-fourths or less as long; 
fertile lemma 2.9-3.2 mm. long, black to dark brown; anthers 1.6-1.9 mm. long; stigmas 
purple; caryopsis 2.2-2.4 mm. long. Chromosome number n = 18 from a Costa Rican 
specimen. 

Pacific slope, 850-1,400 m. elevation. Known from Tilaran, Mon- 
teverde, the Meseta Central, and Canas Gordas. Blooming July to 
February. Central Mexico to Colombia. 

Lasiacis rugelii (Griseb.) Hitchc., Bot. Gaz. (Crawfordsville) 
51:302. 1911, var. pohlii Davidse, Ann. Missouri Bot. Gard. 64:375. 
1977. Panicum rugelii Griseb., Cat. PI. Cuba 233. 1866. Figure 108. 

Perennial; culms caespitose, 1-5 m. long, erect below, weak and arching and climbing 
into brush, occasionally in part procumbent and rooting, internodes hollow, 3-6 mm. 
thick, usually glabrous or with a line of hairs on one side or entirely puberulent; nodes 
glabrous; sheaths densely puberulent; overlapping margin ciliate; auricular hairs 1.5 
mm. long, pseudopetiole 1-3 mm. long; ligule an inconspicuous whitish membrane, 0.4 
mm. or less long; leaf blades ovate-lanceolate to lanceolate, 4-7 cm. long, 8-15 mm. wide, 
glabrous or minutely puberulent; base asymmetric, abruptly narrowed to nearly trun- 
cate. Panicle usually not fully exserted, 3-7 cm. long, the longest branch 3.5 cm. or less 
long; branches ascending to spreading, pubescent or scabrid. Spikelets globose, 3.6-4.2 
mm. long; first glume 1.7-2.5 mm. long, 7-9-nerved; second glume 9-nerved; lower 
(sterile) lemma 9-nerved, with a palea at least half as long but lacking a flower, upper 
(fertile) lemma 3.8-4.0 mm. long, brown; caryopsis 2.2-2.4 mm. long. 

Rain forests, shaded roadsides, riverbanks; elevation 500-700 m. 
Blooming July to January. Known in Costa Rica from Pejibaye (the 
type), Turrialba, and La Palma (Volcan Arenal). Guatemala to 
Panama. 

This variety replaces var. rugelii in Central America. It differs from 
var. rugelii in having the culm internodes glabrous or with only a line 
of puberulence, var. rugelii having pubescent internodes, as well as in 
having smaller, more globose spikelets. 

Lasiacis ruscifolia(H.B.K.) Hitchc., Proc. Biol. Soc. Wash. 24:145. 
1911, var. ruscifolia. Panicum ruscifolium H.B.K., Nov. Gen. & Sp. 
PL 1:101. 1816. Lasiacis glabra Swallen, Ceiba 4:287. 1955. 

Caespitose perennial; culms 1-8 m. long, erect at the base, arching, the upper parts 
leaning on brush; internodes woody, usually hollow, 5-12 mm. thick, variously glabrous 
or with a single line of pubescence, or puberulent, or papillose-pubescent; nodes glabrous 
or puberulent; sheaths papillose-hispid with hairs up to 3.5 mm. long, or puberulent or 
glabrous; overlapping sheath margin ciliate; auricular hairs up to 3 mm. long; ligule 




FIG. 108. Lasiacis rugelii var. pohlii. A, base of plant; B, flowering branch; C, 
spikelet. 



298 



BURGER: FLORA COSTARICENSIS 299 

usually inconspicuous, 0.3-1.0 mm. long, glabrous or ciliate; leaf blades ovate to lance- 
olate, 4-16 cm. long, 10-56 mm. wide, with an asymmetric clasping base that is usually 
ciliate with hairs to 3 mm. long. Panicle rather dense, 2-22 cm. long, the longest branch 
1-9 cm. long, the lower branches widely separated and spreading. Spikelets globose, 
2.6-4.0 mm. long; first glume 1.0-2.2 mm. long, 9-13-nerved; second glume 11-13-nerved; 
lower (sterile) lemma lacking a flower, 11-13-nerved, its palea at least two-thirds as long 
as the lemma; upper (fertile) lemma 2.8-3.6 mm. long, dark brown to grayish black; 
anthers 1.4-2.3 mm. long, white; stigmas white; palea usually deeply concave; caryopsis 
2.0-2.5 mm. long. Chromosome numbern = 18. 

Dry, rocky savannas, gallery forests; common in northern 
Guanacaste; Barranca; La Garita; elevations usually below 500 m. 
Blooming mostly June to February. Northern Mexico to northwestern 
South America (Colombia, Venezuela, and Ecuador); Cuba and 
Jamaica. 

Var. velutina (Swallen) Davidse, Ann. Missouri Bot. Gard. 64:375. 
1977. L. velutina Swallen, Ceiba 4:288. 1955. 

This variety has velutinous leaf blades and pilose panicle branches. 

Some of our specimens from Guanacaste approach this in leaf pubes- 
cence, but lack pilose panicle branches. Honduras; Venezuela. 

Lasiacis scabrior Hitchc., Proc. Biol. Soc. Wash. 40:85. 1927. 

Caespitose perennial; culms erect or arching and clambering over vegetation, 1-6 m. 
tall; internodes up to 13 mm. thick, hollow, woody, papillose-pubescent or puberulent 
near the apex or in a vertical line; nodes glabrous; sheaths Usually pubescent or villous, 
the hairs up to 2 mm. long, rarely becoming glabrous with age; overlapping margin and 
throat ciliate, the hairs 2.0-3.5 mm. long; ligule a conspicuous, usually dark brown 
lacerate membrane, 3.5-7.0 mm. long, glabrous, appressed-pubescent or ciliate, the hairs 
to 3.0 mm. long; leaf blades linear to lanceolate, 6-16 cm. long, 10-30 mm. wide; upper 
surface scabrid or puberulent along the midrib, especially toward the base; lower surface 
usually densely puberulent, or becoming glabrous; base asymmetric; margin scabrid. 
Panicle usually 4-9 cm. long, rather dense, nearly spherical, the longest branch 1-5 cm. 
long; base always included in the upper sheath. No large terminal inflorescence present, 
but numerous inflorescences borne on secondary branches; panicle branches usually 
pubescent or densely puberulent below, scabrid above. Spikelets obovoid, 3.5-4.5 mm. 
long; first glume 1.2-2.8 mm. long, 7-11-nerved; second glume 9-13-nerved; lower 
(sterile) lemma 11-13-nerved, its palea two-thirds as long or longer; flower lacking or 
rudimentary; upper (fertile) lemma 3.5-3.6 mm. long, dark brown; anthers ca. 2 mm. 
long, white; caryopsis 2.1-2.3 mm. long. 

Clearings, trails, margins of wet forests; sea level to 1,100 m. eleva- 
tion. Northern Costa Rica to the Panamanian border. July to April. 
Oaxaca and Vera Cruz, Mexico, to Colombia, Ecuador, and Peru. 

Lasiacis sloanei (Griseb.) Hitchc., Bot. Gaz. (Crawfordsville) 
57:302. 1911. Panicum sloanei Griseb., Fl. Brit. W. Ind. 551. 1864. 



300 FIELDIANA: BOTANY 

Panicum latifolium Hamilt. Prodr. PI. Ind. Occ. 10. 1825, non P. 
latifolium L., 1753. 

Caespitose perennial; culms erect or clambering, 1-6 m. long; internodes hollow, 4-10 
mm. thick, glabrous or with a vertical line of puberulence; nodes glabrous; sheaths 
glabrous except for dilation on the upper margin and throat; auricular hairs up to 3 mm. 
long; pseudopetioles up to 3 mm. long, usually pubescent; ligule membranaceous, 0.5-1.0 
mm. long, ciliolate or ciliate; leaf blades 8-18 cm. long, 13-45 mm. wide, ovate to lance- 
olate; upper surface puberulent or scabrous at the base of the midrib or along its length, 
otherwise shiny and glabrous on both surfaces; base asymmetrical. Panicle open, with 
relatively few, short-pedicellate spikelets appressed to the branches; length 6-34 cm.; 
longest branch 2-15 cm. long. Spikelets 4.0-5.3 mm. long, first glume 1.5-2.6 mm. long, 
7-9-nerved; second glume 9-13-nerved; lower (sterile) lemma 9-13-nerved, with a palea at 
least three-fourths as long; flower lacking or staminate; anthers 1.5-2.0 mm. long or 
sometimes rudimentary; upper (fertile) lemma 3.8-4.3 mm. long; anthers 1.8-2.2 mm. 
long, white; stigmas white; caryopsis 2.3-2.6 mm. long, whitish. Chromosome number 
n = 18. 

Moist forest margins, in brush and thickets along roadsides. Eleva- 
tions below 1,000 m. Northwestern Guanacaste; Pandora; Rio Terraba 
below Boruca; common in the canyon of the Rio Reventazon at CATIE 
at Turrialba. July to March. Northeastern Mexico to Colombia, Ven- 
ezuela, and Ecuador; Greater Antilles. 

Lasiacis sorghoidea (Desv. ex Hamilt.) Hitchc. & Chase, Contr. 
U.S. Natl. Herb. 18:338. 1917., var. sorghoidea. Panicum sor- 
ghoideum Desv. ex Hamilt. , Prodr. PI. Ind. Occ. 10. 1825. 

Caespitose perennial; culms 1-10 m. long, erect at the base, often coarse, arching and 
leaning on vegetation; internodes woody, 5-15 mm. thick, hollow, variously glabrous, 
papillose-pubescent, or with a single line of pubescence; nodes glabrous; sheaths often 
papillose-pubescent, especially toward the apex, the hairs up to 3.5 mm. long, rarely 
glabrate; overlapping margin and throat ciliate, the hairs up to 3 mm. long; collar 
densely pubescent; ligule inconspicuous, usually 0.3-1.5 mm. long, usually ciliate; leaf 
blades elliptic-lanceolate to linear-lanceolate, 6-23 cm. long, 6-46 mm. wide, the upper 
surface usually puberulent, rarely heavily pubescent; lower surface usually velutinous or 
puberulent. Panicle usually large and prominent, 5-35 cm. long, the branches usually 
ascending, spreading at maturity. Spikelets obovate to elliptic, usually purple when 
immature, 3.0-4.3 mm. long; first glume 1.2-2.7 mm. long, 7-11-nerved; second glume 
9-13-nerved; lower (sterile) lemma 9-11-nerved, with a palea half or more as long as the 
lemma; with or without a staminate flower; anthers 1.7-2.0 mm. long; upper (fertile) 
lemma 2.9-3.8 mm. long, dark brown, with a dorsal indentation; anthers 1.9-2.3 mm. 
long; caryopsis 1.8-2.3 mm. long. Chromosome number n = 18. 

Forest margins, brushy areas, roadsides; mostly at elevations below 
1,100 m. Mountains of western Costa Rica, from Guanacaste to the 
Panamanian border. October through May. Oaxaca and Veracruz, 
Mexico, to Brazil and Argentina; West Indies. 

Lasiacis standleyi Hitchc., Proc. Biol. Soc. Wash. 40:86. 1927. L. 



BURGER: FLORA COSTARICENSIS 301 

longiligula Swallen, Ann. Missouri Bot. Gard. 30:232. 1943. L. lucida 
Swollen, Ann. Missouri Bot. Gard. 30:231. 1943. 

Creeping perennial, the culms rooting at the nodes, the plants lacking strong central 
canes; culms with terminal growths erect or scrambling in brush for several meters; 
internodes 2-4 mm. thick, hollow, thin- walled, puberulent toward the apex and with a 
longitudinal line of puberulence or rarely pubescent; nodes glabrous; sheaths variously 
puberulent, pubescent, or papillose-hispid with hairs to 3 mm. long, occasionally gla- 
brous; overlapping margin ciliate with hairs to 2.5 mm. long; collar glabrous or puberu- 
lent; ligule a prominent, usually dark brown lacerate membrane, 4.5-9.0 mm. long, 
ciliate on one or both margins with hairs to 3 mm. long; leaf blades 10-18 cm. long, 8-35 
mm. wide, broadly elliptic-lanceolate to linear, upper surface usually strongly scabrous, 
puberulent, hispidulous, or glabrous; base asymmetric; margins sometimes undulate. 
Panicle rather compact, 7-27 cm. long, the longest branch 2-15 cm. long. Spikelets 
3.7-5.0 mm. long; first glume 9-13-nerved; lower (sterile) lemma 11-13-nerved, with a 
palea one-fourth or less as long, lacking a flower; upper (fertile) lemma 3.4-4. 1 mm. long; 
anthers white; stigmas purple; caryopsis 2. 1-2.4 mm. long. Chromosome number n = 18. 

Cloud and montane forests, from 600 to 2,000 m. elevations; in for- 
ests, clearings, along trails and in brush. Mountains of western Costa 
Rica, from northern Guanacaste to the Panamanian border. October to 
April. Guatemala to Colombia, Venezuela, and Ecuador. 

LEERSIA Swartz 
Nomen Conservandum 

REFERENCE: G. L. Pyrah, Taxonomic and distributional studies in 
Leersia (Gramineae), Iowa State J. Sci. 44:215-270. 1969. 

Perennial caespitose or rhizomatous grasses; inflorescence a terminal panicle. 
Spikelets consisting of a naked laterally compressed and keeled awnless floret; glumes 
reduced to minute ridges or a minute cupule at the tip of the pedicel; lemma strongly 
keeled, 5-nerved; palea keeled, 3-nerved; stamens 1-6; disarticulation below the floret, 
the cupule remaining on the pedicel. 

Leersia is a genus of about 17 species, most of them occurring on wet 
soil or in marshes in temperate or tropical regions of the entire world. 
The genus is apparently closely related to Oryza, from which it differs 
in lacking sterile florets below the fertile one, and in the lack of awns. 
The plants often form large, tangled colonies in marshy areas. The 
foliage in some species, notably L. hexandra, bears minute barbs that 
cause painful scratches in the human epidermis. (Oryzoideae: 
Oryzeae.) 

KEY TO SPECIES OF Leersia 

la. Spikelets pectinate-ciliate, narrowly elliptical, 3-5 mm. long; stamens 6; plants 
rhizomatous, in wet places L. hexandra 



302 FIELDIANA: BOTANY 

Ib. Spikelets not ciliate, usually glabrous, broadly elliptical, 2-3 mm. long; stamens 2; 
plants caespitose, in upland forests L. ligularis var. grandifiora 

Leersia hexandra Swartz, Prodr. Veg. Ind. Occ. 21. 1788. Figure 
109. 

Plants perennial; culms 25-150 cm. long, decumbent and rooting at lower nodes; 
rhizomes slender, elongated; plants sometimes floating in shallow water, branching 
common from rhizomes or decumbent portions of stems; culms 1.0-3.5 mm. thick, hollow, 
glabrous or retrorsely scabrous; nodes retrorsely pubescent; sheaths strongly scabrous 
to glabrous, the margins ciliate, midrib somewhat keeled, upper margins auriculate, the 
auricles acute, joined to the ligule; ligules membranaceous, 1-6 mm. long; blades flat, 
5-25 cm. long, 3-15 mm. wide, from strongly scabrous to glabrous. Peduncle smooth, up 
to 11 cm. long; panicle narrow, open, rather simple, 5-15 cm. long, the branches few. 
Spikelets subsessile, imbricated along the slender, zigzag branchlets, elliptic-oblong, 
apiculate, 3-5 mm. long, 1.0-1.5 mm. wide; lemma and palea of equal length, but the 
lemma much wider; keels of lemma and palea strongly scabrous-ciliate; margins, nerves, 
and internerves of lemma somewhat scabrid; spikelets whitish or pink; stamens 6, 2-3 
mm. long. Chromosome number n = 24 from Costa Rican material. 

Common in wet places, ditches, moist pastures, marshes, sometimes 
floating in shallow water, often forming enormous stands in marshes, 
as at Laguna de Arenal. Widespread in Costa Rica from sea level to 
1,400 m. elev. Blooming probably yearlong. Subtropical and tropical 
regions of both hemispheres; in North America from the southeastern 
United States to Texas; southern Mexico to southern South America. 

Pyrah has pointed out that there is practically no seed set in this 
species. In the sites where it grows, it is able to spread very freely by 
vegetative means. Because of the strongly scabrous sheaths, the 
plants often cause severe scratches, which readily become infected. 

Leersia ligularis Trin., Mem. Acad. Imp. Sci. St.-Petersbourg, 
Ser. 6, Sci. Math., Seconde Pt. Sci. Nat. 5:168. 1839. var. grandiflora 
(Doell) Pyrah, Iowa State J. Sci. 44:236. 1969. L. distichophylla Bal. 
and Poit, Bull. Soc. Hist. Nat. Toulouse 12:221. 1878. L. grandiflora 
(Doell) Prodoehl, Bot. Arch. 1:219. 1922. Figure 109. 

Plants perennial; culms decumbent to erect, to 2 m. tall, sometimes rooting at lower 
nodes, unbranched, hollow; nodes glabrous to retrorse-pubescent; leaves numerous, the 
lower ones with overlapping sheaths; upper sheaths shorter than the internodes; midribs 
of sheaths somewhat keeled above; sheath auricles present, acute, united to the edges of 
the ligule; ligules 1-4 mm. long, membranaceous; blades up to 40 cm. long and 25 mm. 
wide, glabrous or hispid on the upper surface. Peduncle glabrous; panicle up to 45 cm. 
long, ovoid, very open; branches 1-4 at the lower nodes. Spikelets broadly elliptical, 2-3 
mm. long, 1.2-1.6 mm. wide, subsessile along the outer fourth of the spreading branches, 
glabrous or slightly scabrid; anthers 2, 1.0-1.5 mm. long. 

Occasional in the Meseta Central; Rincon de la Vieja; elevations 




FIG. 109. Leersia species. L. hexandra: A, inflorescence; B, spikelet; L. ligularis, var. 
grandiflora: C, inflorescence; D, spikelet. 



303 



304 FIELDIANA: BOTANY 

900-1,100 m., in rocky open woods or brush. Blooming October to 
June. Guatemala to Colombia; Brazil, Paraguay, Argentina. 

LEPTOCHLOA Beauvois 

Annual or perennial grasses. Inflorescence a panicle of slender, 1-sided racemes, 
arranged racemosely along an elongated common rachis; spikelets short-pedicellate, 
appressed in 2 rows along the lower sides of a slender triquetrous rachis, somewhat 
overlapping. Spikelets laterally compressed and keeled, of 2-6 florets, disarticulating 
above the glumes and between the florets, the rachilla extended above the ultimate 
fertile floret and often bearing a minute or moderate-sized rudiment at its apex; glumes 
1-nerved, narrow, acuminate; lemmas 3-nerved, the lateral nerves close to the margins, 
the apex bifid and sometimes bearing a short awn from the split; palea nearly as long as 
the lemma; anthers 2 or 3, small; caryopsis free, angular, grooved on the side opposite 
the embryo. 

Leptochloa is a genus of about 20 species of rather weedy grasses, 
distributed in warm temperate and tropical regions of both hemi- 
spheres. In spikelet structure, it is similar to such genera as Gouinia, 
Triplasis, and Eragrostis. Because of the arrangement of the nearly 
sessile spikelets in two rows along the simple panicle branches, au- 
thors have sometimes placed the genus in the tribe Chlorideae. 
(Chloridoideae: Eragrosteae.) 

KEY TO SPECIES OF Leptochloa 

la. Sheaths more or less papillose-hirsute; glumes nearly as long as spikelet 

L. filiformis 

Ib. Sheaths glabrous; glumes much shorter than spikelet 2 

2a. Ligule a ciliolate membrane 0.3-0.7 mm. long; lemmas often awned L. virgata 
2b. Ligule a dense row of stiff white hairs, 1.5-3.0 mm. long; lemmas awnless 

L. scabra 

Leptochloa filiformis (Lam.) Beauv., Ess. Nouv. Agrost. 71, 166. 
1812. Festuca filiformis Lam., Tabl. Encycl. 1:191. 1791. Figure 110. 

Caespitose annual; plants 10-130 cm. tall; culms erect, unbranched or branched from 
the base, up to 3 mm. thick, hollow, glabrous; nodes glabrous; sheaths mostly overlap- 
ping, more or less papillose-hirsute; ligule a lacerate-ciliate membrane, 0.5-1.5 mm. long, 
decurrent on the sheath margins; blades flat, glabrous or minutely scabrid, 4-23 cm. 
long, 3-9 mm. wide. Peduncle glabrous, exserted 3-15 cm.; inflorescence solitary, termi- 
nal, oblong, 5-50 cm. long, a raceme of simple racemose branches, borne singly or several 
at one node along the rachis; branches up to 10 cm. long, stiffish, slender, the rachis 
triquetrous, bearing short-pedicellate appressed spikelets in 2 rows along the lower 2 
sides. Spikelets 2-3-flowered, 1.8-3.0 mm. long; glumes nearly as long as the spikelet; 
first glume subulate, keeled, 1-nerved, 1.3-2.0 mm. long; second glume narrowly lan- 
ceolate, keeled, 1-nerved, 1.5-2.0 mm. long; lemmas 1.1-1.8 mm. long, ovate, acute, 
keeled, slightly bifid at the apex, awnless, the keel and lateral nerves finely ciliate; palea 
nearly as long as the lemma; rachilla prolonged beyond the upper floret and bearing a 
minute rudiment at its tip; anthers 2, 0.2-0.3 mm. long, yellow. 




FIG. 110. Leptochloa species. L. filiformis: A, panicle; B, spikelet; L. virgata: C, 
spikelet; L. scabra: D, spikelet. 



305 



306 FIELDIANA: BOTANY 

Weedy open areas at low elevations; common in Guanacaste. June to 
October, probably yearlong. Southern United States to Panama; West 
Indies; South America. 

Leptochloa f il i form is X L. virgata. 

A large, vigorous specimen intermediate between these species and 
possessing defective pollen, was collected from Finca la Taboga (Pohl 
& Davidse 10133). It is a probable hybrid of these species, which are 
common in the immediate area. 

Leptochloa scabra Nees, Agrost. Bras. 435. 1829. Figure 110. 

Caespitose annual, in small clumps; plants 90-120 cm. tall; culms erect, branching from 
the lower nodes, up to 6 mm. thick, hollow, glabrous; nodes glabrous, constricted; 
prophylla up to 12 cm. long; sheaths mostly overlapping, glabrous; ligule a dense row of 
stiff, white hairs, 1.5-3.0 mm. long; blades up to 50 cm. long, 6-14 mm. wide, minutely 
scabrid, the margins very scabrous; dewlap purple. Peduncle mostly included in the 
upper sheath; inflorescence solitary, terminal, open-cylindrical, up to 40 cm. long, com- 
posed of numerous lax racemes attached singly or in pairs along the length of the rachis; 
racemes 7-10 cm. long; spikelets rather densely arranged in 2 rows along the lower sides 
of the rachis of the simple branch, overlapping at about 30 inclination to the rachis. 
Spikelets pale, 3.7-4.5 mm. long, with 3-6 florets, narrowly elliptical in outline; glumes 
and florets keeled; first glume ovate, acuminate, 1-nerved, 0.7-1.1 mm. long; second 
glume similar, 1-nerved, 1.2-1.7 mm. long; lemmas 2.3-1.4 mm. long, the upper ones 
shorter than the lower, ovate-oblong, abruptly acuminate or apiculate, 3-nerved, the 
lower part of keel and marginal nerves softly ciliate; palea equal to the lemma or slightly 
exceeding it; anthers 3, 0.2-0.3 mm. long; rachilla prolonged beyond the uppermost floret 
as a naked bristle. 

Uncommon; railroad yard at Limon, Siquirres, Zent, Rio San Car- 
los; open areas at low elevations. June to December. Louisiana and 
Mexico to Costa Rica; West Indies; Venezuela and Colombia to Peru 
and Brazil. 

Leptochloa virgata (L.) Beauv., Ess. Nouv. Agrost. 71, 166. 1812. 
Cynosurus virgatus L., Syst. Nat. ed. 10, 2:876. 1759. Figure 110. 

Caespitose, in small clumps; plants 40-110 cm. tall, erect; branching mostly from base 
and lower nodes; basal portions of culms sometimes decumbent and rooting; culms 2-3 
mm. thick, hollow, glabrous; sheaths glabrous, shorter or longer than the internodes; 
ligule a ciliolate membrane, 0.3-0.7 mm. long; blades 10-26 cm. long, 7-10 mm. wide, 
glabrous. Peduncle exserted 5-28 cm.; inflorescence solitary, terminal, 10-22 cm. long, of 
few to many lax racemes, attached singly or whorled, floriferous to the base, 7-11 cm. 
long; spikelets overlapping, appressed laterally to the lower sides of the rachises. 
Spikelets often purplish, 2.5-3.6 mm. long; glumes scabrous on the keel, the first 1.2-1.6 
mm. long, 1-nerved, subulate to narrowly lanceolate, second glume 1.8-2.3 mm. long, 
1-nerved, narrowly lanceolate; florets 3-5; lowermost lemma 1.8-2.2 mm. long, the upper 
ones shorter, keeled, narrowly ovate, slightly bifid at the apex, sometimes bearing an 
awn up to 2.2 mm. long (often only the lowermost lemma awned); lateral nerves margi- 
nal, softly ciliate on the upper half, the keel glabrous; palea nearly as long as the lemma; 



BURGER: FLORA COSTARICENSIS 307 

ultimate segment of the rachilla bearing a rudiment of varying size; anthers 2, 0.2-0.3 
mm. long, yellow or purplish. Chromosome number n = 20 from Costa Rican material. 

Disturbed soil of fields, roadsides, pastures, and forest margins; low 
elevations, mostly near the Pacific Coast; Limon area. March to De- 
cember, possibly yearlong. Southern United States and Mexico to 
Argentina; West Indies. 

LEPTOCORYPHIUM Nees 

Caespitose perennial from deeply buried hard cormose bases; inflorescence a terminal 
panicle. Spikelets dorsally compressed, disarticulating whole from the pedicel; first 
glume lacking or represented only by a cupule at the tip of the pedicel; second glume and 
sterile lemma subequal, about as long as the fertile floret, both strongly ribbed and 
covered with long silky hairs arising from the nerves; sterile lemma lacking a palea or 
flower; fertile floret chartaceous, brown, its edges not inrolled; palea similar, about equal 
to the lemma, its tip not enclosed by the lemma. 

A small genus of one or two species of savanna grasses, ranging from 
Mexico to Argentina. The genus appears to be closely related to An- 
thaenantia of the southern United States. (Panicoideae: Paniceae.) 

Leptocoryphium lanatum (H.B.K.) Nees, Agrost. Bras. 84. 1829. 
Paspalum lanatum H.B.K. , Nov. Gen. & Sp. 1:94, pi. 29. 1816. Fig- 
ure 111. 

Perennial, in small hard clumps, the bases of the plants hard, cormose, buried in soil; 
plants 60-90 cm. tall, erect, the leaves mostly basal, their sheaths breaking down into 
harsh fibers; culms unbranched, 1-2 mm. thick, smooth, pithy; nodes dark colored, 
glabrous; leaf sheaths glabrous except long-pilose on the sheath auricles; ligule a minute 
ciliate membrane, ca. 0.2 mm. long; leaf blades mostly involute, up to 40 cm. long, 2-3 
mm. wide, glabrous except long-pilose on their lower margins, the upper surface 
strongly ridged; uppermost blade much reduced. Peduncle elongated, slender, glabrous. 
Panicle solitary, terminal, slender, cylindrical but loose, 8-15 cm. long, 1-3 cm. wide, the 
short branches ascending; aspect grayish and fuzzy. Spikelets ascending, appressed to 
the branches, dorsally compressed, 3.5-4.0 mm. long, silky because of the long grayish or 
white hairs which densely cover them. The tip of the pedicel is dilated into a hollow 
cupule from which the spikelet disarticulates, and which may represent a reduced first 
glume. Second glume and sterile lemma 3.2-3.7 mm. long, strongly 5-7-nerved, the 
internerves thin and translucent; nerves densely beset with papillose-based silky hairs 
up to 2 mm. long, either appressed or spreading at right angles to the spikelet; fertile 
floret narrowly ovate, acute, the lemma and palea similar, faintly nerved, their tips 
hyaline; margins of the lemma covering the lower portions of the palea but not the tip; 
anthers 3, purple, ca. 2.5 mm. long. Chromosome number n = 10 from a specimen from 
Honduras. South American reports indicate n = 20 as well. 

This is one of the most xeric of the savanna grasses, found on very 
dry sites, especially on volcanic tuff deposits. The deeply buried plant 
bases afford protection from fires. Many specimens have charred basal 







FIG. 111. Leptocoryphium lanatum. A, panicle; B, buried plant base; C, spikelet; D, 
caryopsis; E, fertile floret. 



308 



BURGER: FLORA COSTARICENSIS 309 

leaves, indicating the frequency of fires in these habitats. Flowering, 
as in many savanna grasses, is synchronous over large areas and is 
completed quickly. Dry savannas, in Costa Rica under 300 m. but 
elsewhere to 1,000 m.; northern Guanacaste, Buenos Aires, Boruca, 
Carias Gordas; not common. February to July. Mexico to Argentina. 

LITHACHNE Beauvois 

Caespitose herbaceous perennials. Spikelets unisexual. Pistillate spikelets: Solitary, 
terminal on slender clustered axillary peduncles, sometimes with 1-several pedicellate 
staminate spikelets below the pistillate one; glumes of pistillate spikelets equal, green, 
herbaceous, many-nerved, caudate-ovate, much exceeding the floret; floret 1, bony, 
shining, the lemma obpyramidal, truncate, cucullate, laterally compressed, borne on a 
thick attached rachilla internode; margins of lemma clasping a bulging palea of bony 
texture; disarticulation above the glumes which may later fall from the pedicel; pedicel 
flattened, keeled, enlarged below the tip. Staminate spikelets: Either borne below the 
pistillate one on axillary peduncles or in a small terminal panicle. Staminate spikelet: A 
naked floret lacking glumes, borne on a short, thickened stipe above the point of disar- 
ticulation; lemma and palea about equal, narrowly lanceolate, thin and membranaceous, 
white; lemma 3-nerved, awnless; palea similar, 2-nerved; anthers 3, nearly as long as the 
floret, borne on very short filaments; floret disarticulating from the pedicel after flower- 
ing. 

Lithachne is a small genus of forest-inhabiting bambusoid grasses of 
the tropics of the western hemisphere. The genus is related to Olyra, 
Raddia, Cryptochloa, and other herbaceous bambusoids. The asym- 
metric, truncate-based leaf blades and the rigid, helmet-shaped fertile 
florets are distinctive. Earlier authors interpreted the spikelets as 
panicoid in structure, and assigned the genus to the Panicoideae. Leaf 
anatomy indicates that it is bambusoid. (Bambusoideae: Olyreae.) 

Lithachne paud flora (Swartz) Beauv. ex Poir., Diet. Sci. Nat. 
27:60. 1823. Olyra pauciflora Sw., Prodr. Veg. Ind. Occ. 21. 1788. 
Figure 112. 

Caespitose perennial; clumps usually small; culms erect or arching, 20-75 cm. tall, 
simple; internodes glabrous, ca. 1 mm. thick, hollow; nodes shrunken in dry specimens, 
with a sharp ridge below and above the node; lower internodes elongated, the upper 
much shorter; lower sheaths bladeless or with reduced blades, much shorter than the 
internodes; upper sheaths overlapping, the foliage clustered near the apex of the culms; 
sheaths sparsely hispidulous, slightly keeled; ligules membranaceous, minute, ca. 0.5 
mm. long; leaf blades 4-10 cm. long, 1.5-3 cm. wide, lanceolate, asymmetric, one side 
broad and truncate at the base, the other narrow and rounded; pseudopetiole present 
between sheath and blade, ca. 1 mm. long, flattened, sparsely hirsute above; midrib of 
the blade ends just above the apex of the pseudopetiole. Successive leaf blades on a culm 
are of two types. If one leaf has the broad truncate base to the left of the midrib, the 
leaves above and below it will have it to the right. Pistillate spikelets: Glumes green, 
herbaceous, 9-11 mm. long, about equal; first glume 9-nerved, the second 7-nerved; 
floret bony, at first shining white, at maturity dark brown with whitish veins, truncate, 




JE/I 



FIG. 112. Lithachne pauciflora. A, blooming culm; B, pistillate spikelet; C, staminate 
spikelet; D, pistillate floret on its rachilla internode. 



310 



BURGER: FLORA COSTARICENSIS 311 

cucullate, 4-5 mm. long, including the short projecting basal stipe; edges of lemma 
inrolled and concealing the margins of the bulging palea; both lemma and palea glabrous; 
caryopsis rotund, completely filling the floret. Staminate inflorescence, if present, soli- 
tary at the tip of the culm, a simple, few-flowered panicle, borne on a short peduncle; 
staminate spikelets also born racemosely on the peduncles of the pistillate ones. Stami- 
nate spikelets: Consisting of a naked floret on a short stipe; lemma and palea ca. 5-6 mm. 
long, thin, white, membranaceous, glabrous, the lemma lance-acuminate, 3-nerved; 
palea 2-nerved. Chromosome number n = 11 from Costa Rican material. 

Moist forests and cacao groves, Atlantic and Pacific slopes 20- 
1,250 m. elevation; scattered in forests but not rare; apparently 
blooming yearlong. Terminal staminate inflorescences are rarely found 
on specimens. Mexico to Ecuador, Brazil, and northern Argentina. 

LOLIUM Linnaeus 

Annual or weakly perennial caespitose or rhizomatous grasses; inflorescence a bal- 
anced terminal spike; spikelets placed edgewise, with the backs of the lemmas toward 
the rachis; first glume lacking except in the spikelet at the end of the rachis; second 
glume placed away from the rachis; florets several; glume and lemmas several-nerved; 
disarticulation at base of each floret; lemmas awned or awnless. 

In the past, this genus was usually placed in the barley tribe 
(Triticeae). Since numerous spontaneous hybrids with members of the 
genus Festitca of the tribe Poeae are known, but none with genera of 
the Triticeae, it is better placed in the Poeae. Ryegrass, Zacate ray, 
Ray Ingles. 

Lolium perenne L., Sp. PI. 83. 1753. Figure 113. 

Perennial or annual; mostly caespitose but producing rhizomes in wet sites; plants 
10-90 cm. tall; culms glabrous, 1-3 mm. thick, hollow; nodes glabrous; sheaths glabrous; 
ligule a thin membrane, up to 2 mm. long; leaf blades 3-20 cm. long, 2-6 mm. wide, with 
prominent auricles; inflorescence slender, to 30 cm. long; spikelets appressed to the 
rachis, the lower ones remote, the upper ones longer than the rachis internode adjacent, 
7-20 mm. long, with 4-14 florets; second glume oblong, 5-7-nerved, shorter than the 
spikelet; lemmas 5-7 mm. long, narrowly elliptical, glabrous, 5-nerved, acute, sometimes 
awned; palea equal to the lemma, scabrid on the nerves; anthers 3, 3-4 mm. long. 

Awned forms of this species occur, and have been given names. 
These forms interbreed freely with the awnless type, and are best 
regarded as agronomic forms of the species. If given taxonomic recog- 
nition, they are to be called var. aristatum Willd. (= var. italicum 
Parn.). Such awned plants are usually distinguished as "Italian rye- 
grass," and the awnless ones as "English" or "perennial ryegrass." 

This species, especially the awned form, has been cultivated for 
forage on the volcanoes of the Cordillera Central. It can be found in 
moist pastures from 1,800 to 2,600 m. elevation on Irazu and Turrialba. 




FIG. 113. Lolium perenne. A, inflorescence; B, plant base; C, awned and awnless 
spikelets. 



312 



BURGER: FLORA COSTARICENSIS 313 

Native to Europe, but now widely naturalized in humid temperate 
climates. 

LORENZOCHLOA J. & C. Reeder 

Densely caespitose perennial tussock grass; leaf blades usually basal, erect, involute, 
terete, rigid, pungent; ligules membranaceous, decurrent; inflorescence a few-flowered 
terminal panicle; spikelets 1-flowered; glumes short, equal, firm, truncate or emargi- 
nate, very broad, very faintly nerved; disarticulation above the glumes; floret much 
longer than the glumes; lemma awned, obscurely 5-nerved, more or less pubescent at the 
acuminate base; awn thickish, stiff, antrorsely scabrid; palea slightly shorter than the 
lemma; lodicules 3, oblong-elliptical. (Pooideae: Stipeae.) 

Lorenzochloa erectifolia (Swallen) J. & C. Reeder, Bol. Soc. Ar- 
gent. Bot. 11:239. 1969. Muhlenbergia erectifolia Swallen, J. Wash. 
Acad. Sci. 21:15. 1931. Parodiella erectifolia (Swallen) J. & C. 
Reeder., Bol. Soc. Argent. Bot. 12:279. 1968. Figure 114. 

Perennial, densely caespitose; culms erect, glabrous, 15-35 (38) cm. tall; leaves mostly 
basal; sheaths smooth or somewhat scabrous; ligule membranous, acute, 2-4 mm. long, 
decurrent onto the somewhat hyaline sheath margins; blades erect, rigid, terete, scab- 
rous, pungently pointed, 5-15 (18) cm. long, narrower than the sheaths at the base; 
panicles narrow, erect, 5-8 cm. long, rather few-flowered, the branches with rather 
conspicuous pulvini in their axils; spikelets appressed to the branches, the pedicels 1-4 
mm. long, rather stout; glumes firm, subequal, 1-1.3 (1.5) mm. long, truncate and usually 
emarginate, obscurely 3-nerved, tinged with bronze and purple; lemma firm, obscurely 
5-nerved, 2.5 mm. long, pubescent along the lower half of the midnerve, and often along 
the margins, pointed and pubescent at the base, the slightly scabrous apex tapering into 
a stout erect or slightly flexuous scabrous awn 3-5 mm. long, with a distinct line of 
demarcation between it and the body of the lemma; palea firm, nearly equalling the 
lemma, often pubescent between the nerves; anthers purplish, 0.6-0.8 mm. long; caryop- 
sis broadly fusiform, light brown, ca. 1.2-1.4 mm. long. Chromosome number 2n = 22. 

The above description was quoted from the description of Parodiella 
erectifolia, since our specimens are too weathered to provide many 
details. This South American species has been collected only twice in 
North America, from the alpine paramo of Chirripo Grande. The 
specimens are: Prov. de San Jose, Chusquea subtessellata paramo, 
elevation 3,500 m., between Refugio and lake at head of Rio Ditkebi, 
G. Davidse 1562, 3 April 1969; Chirripo-Massiv, Quellgebiet des Rio 
Talari, "Valle de los Conejos," chusqueafreie Vegetationsflachen des 
Talbodens, Kaltluftsee, ca. 3,500 m., 16 March 1971, Kuhbier 0401. 
Paramos, 3,400-4,200 m.; Venezuela, Colombia, Peru; southern Costa 
Rica. 

LUZIOLA Jussieu ex Gmelin 

REFERENCE: J. R. Swallen, The grass genus Luziola, Ann. Missouri 
Bot. Card. 52:472-75. 1965. 




JZZt 



FIG. 114. Lorenzochloa erectifolia. A, spikelet; B, floret; C, portion of a plant with 
rigid basal leaves; D, inflorescence. 



314 



BURGER: FLORA COSTARICENSIS 315 

Monoecious aquatic or paludose grasses; spikelets unisexual, in usually separate 
inflorescences, the pistillate inflorescence an axillary panicle (reduced to 2 conjugate 
racemes in L. fragilis), the staminate a terminal panicle or raceme; glumes reduced to a 
minute cupule or absent; floret single, disarticulating from the cupule or pedicel apex; 
pistillate spikelets with equal, many-nerved lemma and palea; lodicules not functional, 
the stigmas laterally exserted from the lemma and palea; caryopsis ovoid or spherical, 
striate, crowned with the persistent style bases, retained within the floret, which usu- 
ally decays into a circle of fibers attached to the caryopsis; staminate spikelets with thin, 
membranous, faintly-nerved lemma and palea; stamens 6. (Oryzoideae: Oryzeae.) 

KEY TO SPECIES OF Luziola 

la. Pistillate inflorescence a single pair of few-flowered reflexed racemes at tip of 
peduncle; staminate inflorescence a simple raceme; culms weak, leafless, submerged 
in water, foliage leaves floating on water surface L. fragilis 

Ib. Pistillate and staminate inflorescences panicles with several to many branches; 
culms ascending or erect, stiff, leafy L. subintegra 

Luziola fragilis Swollen, Ann. Missouri Bot. Gard. 52:474. 1965. 
Figure 115. 

Aquatic; duration indefinite; culms weak and slender, rooted in soil of ponds; sub- 
merged internodes with thin membranaceous, bladeless sheaths; foliage leaves floating 
on top of the water during wet seasons; plants forming dense mats of foliage on drying 
mud during dry seasons; internodes of submerged culms up to 11 cm. long, the inter- 
nodes of the floating portions very short, frequently less than 1 cm. long; nodes slightly 
bearded; culms less than 1 mm. thick, apparently solid. Floating foliage: Sheaths ca. 2 
cm. long, densely villosulous, or the uppermost sparsely so; ligules membranaceous, 
white, 1-2 mm. long; blades 3-6 cm. long, 2-2.5 mm. wide^strongly ridged above, the 
ridges densely covered with minute thick blunt spicules; usually 3-4 floating leaves at the 
tip of the culm; branching abundant just below the water surface; plants monoecious. 
Staminate inflorescence a simple terminal raceme of 3-5 spikelets which are appressed to 
the rachis; raceme borne on a slender, erect, intravaginal peduncle, exserted ca. 1 cm. 
from the mouth of the sheath; pedicels ca. 0.5 mm. long. Glumes lacking; floret 5-7 mm. 
long; lemma and palea very thin and membranaceous, the lemma ca. 7-nerved, the palea 
ca. 4-nerved, both with abundant blunt tricellular microhairs; stamens 6, the anthers 
yellow, 3-4 mm. long. Pistillate inflorescences axillary, from 1 or more nodes below the 
terminal staminate inflorescence; peduncle mostly included in the sheath, up to 3 cm. 
long; branches 2, bijugate at the apex of the peduncle and strongly reflexed in fruit, one 
usually slightly longer than the other; pedicels 0.5 mm. long, appressed to the branches. 
Spikelets 1-9 per branch, 1.8-2.3 mm. long, lanceolate at anthesis, becoming ovoid in 
fruit; glumes absent; lemma stramineous, broader than the palea and enveloping its 
base, with ca. 12-14 nerves; internerve tissue very thin, rotting away after maturity, the 
caryopsis remaining surrounded by the vascular bundles; palea ca. 6-nerved, similar to 
the lemma but narrower; caryopsis broadly ellipsoidal , brown, longitudinally striate, ca. 
2 mm. long, crowned with the persistent style bases. Chromosome number n = 12 from a 
Costa Rican specimen. 

This unusual aquatic grass closely resembles Hydrochloa 
caroliniensis in general aspect and ecology, but differs in the bijugate 
pistillate inflorescence. We have found it in permanent ponds near 




FIG. 115. Luziolafragilis. A, floating culm with inflorescences; B, pistillate inflores- 
cence; C, pistillate spikelets; D, staminate inflorescence; E, staminate spikelet. 



316 



BURGER: FLORA COSTARICENSIS 317 

Buenos Aires, Prov. de Puntarenas, and in several similar ponds in 
Guanacaste, as at Laguna la Calavera. Another colony occurs on the 
road to Hacienda Los Inocentes. Blooming has been observed in De- 
cember and January. Examination of dried pond bottoms later in the 
year showed extensive growth of turfy colonies of the plant, but no 
sign of flowering. I have been able to germinate seed, but the seedlings 
died. 

This species has previously been known only from the type collec- 
tion, from Aquidauana, Mato Grosso, Brazil. Although large gaps are 
common in the distribution patterns of aquatic grasses, it seems likely 
that L. fragilis will eventually be found in intermediate localities. The 
plants seem to require standing water that is permanent or nearly so. 
Finding the plants in such very scattered localities suggests that the 
seeds are transported by water fowl. 

Luziola subintegra Swallen, Ann. Missouri Bot. Gard. 30:165. 1943. 
Figure 116. 

Duration indefinite; plants sprawling and stoloniferous on wet, muddy soil, branching 
abundantly from the rooted nodes of the thick, spongy stolons; culms ascending, 2-4 mm. 
thick, hollow, glabrous and shining; nodes glabrous, conspicuous, brownish; prophylla 
many-nerved, 3-6 cm. long; leaf sheaths mostly longer than the culm internodes, over- 
lapping, somewhat inflated; ligules membranaceous, usually 3-4 cm. long, acuminate to a 
fine point, adnate to the erect sheath auricles; blades stiffish, up to 35 cm. long, 12 mm. 
wide near the middle and tapering to a base narrower than the sheath apex. Pistillate 
inflorescences: 1-several, borne at successive lower nodes of the culms; peduncle short, 
fleshy, strongly bent and emerging extravaginally from the overlapping edges of the 
sheath just above the node; length ca. 4 cm. and broader than long; branches crowded, 
several per node; rachis soft, fleshy, angular; branches stiff, fleshy, strongly retrorse at 
maturity; pulvini prominent, ciliate at their edges. Spikelets appressed to the main 
branches, or 1 or more on a secondary branch, more or less terete, 5-5.5 mm. long; 
glumes reduced to a minute cupule; disarticulation above the cupule; lemma and palea 
equal, lanceolate, blunt; lemma 7-nerved, the nerves prominent, nearly contiguous when 
the spikelet is immature, spreading when distended with the fruit; nerves scabrid; palea 
similar to the lemma, 5-nerved; caryopsis ovoid, olivaceous, shining, slightly striate, 
tipped with the persistent bases of the styles, 1.5-2 mm. long at maturity, remaining 
within the floret; mature spikelet ovoid, tapering to a narrow apical beak; internerve 
tissue not disintegrating. Staminate inflorescence: Single, terminal on the culm, up to 
7 cm. long, narrowly ovoid, with strongly ascending subverticillate branches. Spikelets 
racemose along the panicle branches, more or less terete, narrowly ovoid in outline, 5-6 
mm. long; glumes reduced to a minute cupule; floret disarticulating above the cupule; 
lemma and palea equal, thin, white, membranaceous, faintly 5-nerved; stamens 6, the 
filaments very short, less than 1 mm. long; anthers 3.5-4 mm. long, sulfur yellow to 
reddish. 

Rare; wet meadows and sand bars, at sea level; Las Playitas del Rio 
Bebedero and Barro de Colorado. Blooming in December and January. 
El Salvador to Ecuador, Brazil, and Paraguay; Caribbean Islands. 




FIG. 116. Luziola subintegra. A, staminate inflorescence; B, staminate spikelet; C, 
culm with axillary pistillate inflorescence; D, pistillate spikelet. 



318 



BURGER: FLORA COSTARICENSIS 319 

MELINIS Beauvois 

Plants sprawling, leafy, the foliage densely viscid-hairy and strongly aromatic; 
inflorescence a panicle; spikelets somewhat laterally compressed, oblong in outline, dis- 
articulating below the glumes; first glume minute, nerveless; second glume and sterile 
lemma subequal, lanceolate, strongly ribbed, both bifid at the tip; second glume 7- 
nerved, with a minute awn arising between the lobes; sterile lemma 3-5-nerved, with an 
elongated awn arising between the lobes; palea absent; fertile floret shorter than the 
sterile lemma; its lemma and palea subequal, smooth and shining, thin and translucent; 
lemma ovate, 1-nerved. (Panicoideae: Paniceae.) 

Melinis minuti flora Beauv., Ess. Nouv. Agrost. 54. 1812. Figure 
117. 

Sprawling perennial; culms decumbent and often rooting near the base, up to 180 cm. 
long but usually much shorter, much branched, with erect flowering branches; culms 
solid, pithy, papillose-pilose with spreading hairs; nodes bearded with appressed erect 
hairs; sheaths, except the upper ones, mostly overlapping, densely papillose-pilose, the 
hairs with viscid blobs of odorous resinous material; ligule a dense arc of silky white 
hairs, ca. 1 mm. long; blades velvety on both surfaces, papillose-ciliate on the margins, 
5-15 cm. long, 5-12 mm. wide, flat; peduncle glabrous, 4-10 cm. long; panicles terminal on 
leafy branches, 9-22 cm. long, 2-7 cm. wide, purple, narrow, the branches spreading only 
during anthesis, delicate, densely flowered; spikelets slightly laterally compressed, 
1.9-2.5 mm. long; first glume rotund, 0.2-0.3 mm. long; second glume lanceolate, 5-7- 
nerved, 1.9-2.5 mm. long; sterile lemma similar to the second glume, 1.8-2.4 mm. long, 
3-5-nerved, the awn 5-12 mm. long; fertile floret 1.7-2.0 mm. long, the lemma and palea 
about equal or the palea slightly longer; anthers 3, 1-1.5 mm. long, purple. Chromosome 
number n = 18. 

Roadsides and pastures, especially in the Meseta Central and Gen- 
eral Valley; 700-1,900 m. elevation. This species blooms en masse 
during the short days of November and December, but small amounts 
of bloom may be seen at other times of the year. This species is of 
African origin, but has become widely distributed in the American 
tropics through its use as a forage grass. It is popularly believed that 
Melinis traps ticks by its stickiness and repels mosquitoes by its 
strong odor. Common names: "Molasses grass," Gordura, Calinguero. 

MEROSTACHYS Sprengel 

Caespitose, nonthorny bamboos; rhizomes pachymorphous; internodes cylindrical, 
hollow; culm sheaths with a narrow, reflexed blade; leaf-bearing branches equal, fasci- 
cled, arising from the margins of a flat, plate like me ri stem adnate to the base of the 
internode. Inflorescence a one-sided, rather dense spike, the spikelets solitary or paired, 
in 2 rows along the lower side of the rachis. Glumes usually rudimentary or absent; 
sterile lemmas 2; fertile florets 1-several, the rachilla prolonged beyond the fertile florets 
and bearing a rudimentary floret at its apex; disarticulation below the fertile floret; palea 
grooved, the keels clasping the rachilla internode; lodicules 3, flat, vasculated; anthers 3; 
stigmas 2. (Bambusoideae: Arthrostylideae.) 




FIG. 117. Melinis minutiftora. A, panicle; B, culm internode and leaf; C, hairs with 
sticky globules; D, spikelet; E, apex of sterile lemma; F, fertile floret. 



320 



BURGER: FLORA COSTARICENSIS 321 

This genus is known in Costa Rica by two flowering specimens. They 
are too fragmentary for specific determination, although M. mul- 
tiramea Hack, has been reported from La Palma de San Ramon by 
Standley on the basis of a specimen in the National Museum of Costa 
Rica. 

Merostachys sp. indet. Figure 118. 

Specimens fragmentary, represented by fascicles of up to 10 flowering branchlets, 
these up to 60 cm. long, including the inflorescences; internodes cylindrical, up to 8 mm. 
thick, glabrous; leaves with blades 4-7, borne on the outer portion of the branchlets; 
lower internodes glabrous, naked or with bladeless sheaths; apex of internodes finely 
appressed-silky; sheaths glabrous; auricular bristles conspicuous, 7-12 mm. long; ligule a 
short, thick, minutely ciliolate membrane, ca. 0.5 mm. long; blades flat, ovate 6-9:1, 
acuminate, the base rounded to a pseudopetiole ca. 4 mm. long; blade surfaces glabrous, 
the marginal nerves finely scabrous. Inflorescences terminal on leafy branchlets; spikes 
falcate, one-sided, 4.5-6.5 cm. long, ca. 1 cm. wide; peduncle and rachis finely white- 
silky; spikelets mostly paired and subsessile, one each side of the rachis. Spikelets 11-13 
mm. long, falcate, crowded, brown or purplish; disarticulation above the 2 basal bracts 
(glumes or sterile lemmas); first bract triangular 2.5:1, acute, 1-3-nerved; second bract 
ovate ca. 2.5:1, acute, 7-nerved, rounded on the back, acute, the margins ciliolate near 
the tip; fertile lemma 9.5-10 mm. long, 11-nerved, the margins overlapping at the base; 
surface sparsely pubescent; palea slightly longer, broad, 10-nerved, the 2 ciliolate keels 
close together, clasping a flattened slender rachilla, ca. 8 mm. long, with a minute 
rudiment at its tip; lodicules 3, flat; anthers not seen. 

This species is represented in the Field Museum Herbarium by the 
following flowering specimens from Costa Rica. I have not seen other 
specimens from the country. Prov. Puntarenas, Zapotel, Montes de 
Oro, altitude 1,500 m., May 1961, Otdn Jimenez s.n.; Prov. Alajuela, 
La Palma de San Ramon, altitude 1,050 m., 17 April 1927, Brenes 
5433. Common names are given as Canuela or Carrizo, but these 
names are rather widely applied to different plants. 

MESOSETUM Steudel 

REFERENCE: J. R. Swallen, The grass genus Mesosetum, Brittonia 
2:363-392. 1937. 

Caespitose or stoloniferous grasses; inflorescence a solitary terminal dorsiventral 
spike or spikelike raceme, the spikelets solitary, erect, appressed to the flattened rachis, 
alternating in 2 rows along one side of it, with the first glumes placed toward the midrib. 
Spikelets laterally compressed, the glumes subequal, stiff, nearly as long as the sterile 
lower lemma, folded and sometimes wing-keeled near the tips; first glume 3-nerved; 
second glume 5-nerved; lower lemma usually lacking a flower, its palea well developed; 
upper floret shorter than the lower, with a perfect flower, its lemma coriaceous, boat- 
shaped, 5-nerved, the margins not inrolled, the tip tapering into a narrow blunt beak; 
palea of similar texture, broad, infolding the flower, convex on the back. 




FIG. 118. Merostachys species. A, branch complement, showing one flowering branch; 
B, pair of spikelets; C, terminal floret, showing elongated rachilla internode with a 
terminal rudiment. 



322 



BURGER: FLORA COSTARICENSIS 323 

A small genus of about 30 species, mostly in South America, a few in 
the West Indies and Central America. The genus is related to 
Echinolaena and Eriochloa. (Panicoideae: Paniceae.) 

Mesosetum pittieri Hitchc., Proc. Biol. Soc. Wash. 40:85. 1927. 
Figure 119. 

Duration indefinite; culms 15-40 cm. long, erect or trailing and rooting at the lower 
nodes, unbranched; culms glabrous, hollow, ca. 1 mm. thick; foliage mostly near the 
bases of the culms, the upper 1 or 2 leaf blades much reduced; sheaths somewhat keeled, 
the lower ones pubescent, the upper glabrous except for the papillose-ciliate margins; 
ligule a dense row of stiff short hairs, 0.2-0.5 mm. long; leaf blades 3-4 per culm, the 
uppermost much reduced; blades stiff, the larger ones 5-9 cm. long, 3-5 mm. wide, with a 
thick white marginal band, papillose-pilose above and below or nearly glabrous. Pedun- 
cle included in the upper sheath or exserted up to 7 cm. , slender, stiff, glabrous; spike 3-7 
cm. long, linear, 3-5 mm. wide, the rachis slightly zigzag, ca. 1 mm. wide, flattened, with 
a prominent midrib. Spikelets laterally compressed, the flat sides appressed to the 
rachis; outline V-shaped, the base narrowed into a short narrow stipe ca. 0.5 mm. long 
enveloped by the bases of the glumes; length of spikelet, including the stipe, 5.5-6.2 
mm.; first glume 4.9-5.5 mm. long, oblong-spatulate, winged at the obtuse tip, silky 
along the keel near the base, scabrid above; second glume and sterile (lower) lemma 
subequal, 5.5-6.2 mm. long, both green-mottled and cross-wrinkled near the tip; second 
glume narrowly ovate, slightly winged at the tip, silky along the keel and margins; 
sterile lemma narrowly oblong, blunt and slightly winged at the tip, silky between the 
lateral nerves on the lower half and on the margins near the middle, a conspicuous tuft of 
hairs on the keel one-third below the tip; palea of sterile lemma linear, nearly as long as 
the lemma; fertile floret 4.7-4.8 mm. long, stramineous, minutely roughened; anthers 3, 
ca. 2 mm. long, purple; caryopsis obovate, tan, the embryo prominent, ca. half the 
length of the grain; opposite side of the caryopsis with a dark line running its entire 
length. Chromosome number n = 8. 

We have collected this species in Byrsonima-Curatella savannas of 
Hacienda Murcielago and Hda. Las Animas. In both cases, the plants 
were growing in slightly moist depressions. Elevations 200-300 m. 
Late July, December. This species was previously known only from 
the type locality, near Chepo, Panama and from San Lorenzo, Hon- 
duras. 

MUHLENBERGIA Schreber 

REFERENCES: T. R. Soderstrom, Taxonomic study of subgenus 
Podosemum and section Epicampes of Muhlenbergia (Gramineae), 
Contr. U.S. Natl. Herb. 34:75-189 + pi. 1-14. 1967. J. R. Swallen, The 
awnless annual species of Muhlenbergia, Contr. U.S. Natl. Herb. 
29:203-208. 1947. 

Caespitose or rhizomatous annual or perennial grasses; ligules membranaceous, often 
ciliate; inflorescence an open or contracted panicle; spikelets 1-flowered, disarticulating 
above the glumes, laterally compressed or terete; glumes shorter than or equal to the 
lemma, 1-3-nerved, or nerveless if minute, the first usually smaller than the second; 





B 



FIG. 119. Mesosetum pittieri. A, blooming plant; B, inflorescence; C, spikelet. 



324 



BURGER: FLORA COSTARICENSIS 325 

lemma slender, 3 (-5)-nerved, membranaceous, rounded on the back, tapering to a point, 
usually awned, rarely with minute teeth at the base of the awn; callus short, usually 
bearded; palea about equal to the lemma, 2-nerved. (Chloridoideae: Sporoboleae.) The 
basic chromosome number in Muhlenbergia is consistently x = 10, whereas that of 
Sporobolus is x = 9 or x = 6. 

A genus of about 100 species, mostly of North America, some 
species in South America and a few in temperate Asia. Muhlenbergia 
is similar to Sporobolus, differing in the 3-nerved lemma and usual 
possession of lemma awns, and in the adherent pericarp. Awnless 
species have sometimes been transferred from one genus to the other. 

KEY TO SPECIES OF Muhlenbergia 

la. Spikelets awnless or the lemmas with short awns less than 1 mm. long 2 

Ib. Spikelets awned, awn longer than lemma 4 

2a. Dwarf, much-branched perennials, less than 20 cm. tall 3 

2b. Culms erect, unbranched, 70-100 cm. tall M. nigra 

3a. Panicles exserted, many-flowered M. ramulosa 

3b. Panicles hidden in the densely fascicled leaves, with 3-7 spikelets; paramos of 

Chirripo Grande M . calcicola 

4a. Plants 70-170 cm. tall; culms unbranched; leaf blades 40-70 cm. long; inflores- 
cence 20-40 cm. long M . lehmanniana 

4b. Plants much shorter or culms branched; leaf blades less than 15 cm. long; 

inflorescences less than 15 cm. long 5 

5a. Ligules 1.5-8.0 mm. long (usually over 2.0 mm.) 6 

5b. Ligules less than 1.2 mm. long 8 

6a. Glumes minute, less than 0.5 mm. long, rounded, nerveless; panicles open and 
delicate, spikelets on diverging pedicels longer than the spikelets 

M. implicate, 
6b. Glumes more than 1 mm. long, 1-3-nerved; panicles narrow or congested, 

spikelets short-pedicellate 7 

7a. Leaves mostly basal, sheaths strongly keeled, forming fan-shaped tufts, only one 
small blade at midculm; second glume 3-nerved, obtuse or 3-lobed at apex; paramos 

over 3,000 m M . flabellata 

7b. Leaves distributed along the culms; glumes acuminate, 1-nerved; moist forests, 

1,500-2,100 m M. setarioides 

8a. Glumes of all spikelets similar 9 

8b. One glume of terminal spikelet on inflorescence branches awned, others ob- 
tuse, nerveless M diversiglumis 

9a. Ligules 0.8-1.2 mm. long; panicles very open; pedicels very slender, divergent, 
longer than spikelets M. tenuissima 

9b. Ligules less than 0.5 mm. long; spikelets short-pedicellate, appressed to rachis or 

branches of rather condensed panicles 10 

lOa. Lemmas ciliate; primary panicle branches spreading M. ciliata 

lOb. Lemmas not ciliate; primary panicle branches appressed to rachis 

M. tenella 



326 FIELDIANA: BOTANY 

Muhlenbergia calcicola Swallen, Contr. U.S. Natl. Herb. 29:407. 
1950. Figure 122. 

Perennial, forming flat tufts up to 15 cm. broad, dying in the center; plants 3-4 cm. tall, 
densely crowded; culms branching profusely, their internodes only 2-5 mm. long, a short 
branchlet with fascicled leaves borne at each node; culms 0.5 mm. thick, solid; prophylla 
3.5-4.0 mm. long, broad; sheaths glabrous, ridged, flattened by the densely fascicled 
branches and leaves within; ligule a membrane 0.7-0.9 mm. long; blades 3-14 mm. long, 
1.0-1.5 mm. wide, thick and stiff, flat or folded, ridged on both surfaces, tapering ab- 
ruptly to a boat-shaped tip; the midrib prominent beneath; upper surface bearing minute 
erect spicular hairs. Inflorescence a few (3-7) flowered raceme or simple panicle, con- 
cealed in the upper sheaths, or barely exserted; pedicels stiff, thick, erect, scabrous. 
Spikelets blackish; glumes ovate, acute, the first 1-nerved, 1.4-1.7 mm. long, the second 
sometimes 3-nerved, 1.7-1.9 mm. long; lemma ovate, somewhat keeled, 3-nerved, 
2.5-3.0 mm. long; callus truncate, glabrous; lemma tapering to a short, thick, scabrous 
awn up to 1.0 mm. long; palea flat between the keels, equal to the lemma; caryopsis 
cylindrical, ca. 1 mm. long. 

Known in Costa Rica only from the Valle de Conejos, Chirripo 
Grande, at elevations between 3,400 and 3,800 m. The plants formed 
large mats or tufts in flat moist depressions. November to January. 
Previously known only from the highlands of northwestern Guatemala. 
Muhlenbergia breviculmis Swallen is doubtfully distinct from M . cal- 
cicola, the specimens probably representing young plants of the latter. 

Muhlenbergia ciliata (H.B.K.) Kunth, Rev. Gram. 1:63. 1829. 
Podosaemum ciliatum H.B.K., Nov. Gen. & Sp. 1:128. 1816. Figure 
120. 

Sprawling, delicate, short-lived annual; tufted; culms slender, 15-25 cm. long, 0.3 mm. 
thick, glabrous, branching freely from the lower and middle nodes; prophylla 5-8 mm. 
long; sheaths and blades hispid or nearly glabrous; sheaths much shorter than the inter- 
nodes; ligule a lacerate membrane, ca. 0.3 mm. long; blades reflexed, mostly folded or 
involute, 1.5-3.0 cm. long, 1-2 mm. wide. Inflorescences numerous, terminal on the main 
culm or on leafy branches; panicles 5-9 cm. long, the slender exposed axis bearing 5-8 
slender spreading or reflexed solitary branches, each 1-2 cm. long; spikelets appressed to 
the branches, overlapping. Spikelets 2-3 mm. long, excluding the awns; first glume 
linear to lanceolate, 1-nerved, 0.7-1.2 mm. long, the midnerve often excurrent as a short 
awn; second glume similar, 1.2-1.7 mm. long; lemma slender, lanceolate, strongly 3- 
nerved, 2.1-3.0 mm. long, the callus minutely bearded; marginal nerves more or less 
papillose-ciliate, sometimes nearly glabrous; awn slender, flexuous, 7-17 mm. long; palea 
equal to the lemma; anthers 3, yellow, ca. 0.3 mm. long. Some descriptions state that the 
lemmas are 5-nerved. Examination with the microscope shows that the supposed inter- 
mediate nerves are not vascular bundles, but merely rows of short barbs. 

Moist rocky banks and roadsides. Our only Costa Rican specimen 
was collected along the CIA, 14 km. S of Division, at 1,500 m. eleva- 
tion. December. Mexico to Panama. 

Muhlenbergia diversiglumis Trin., Mem. Acad. Imp. Sci. St.- 





FIG. 120. Muhlenbergia species. M . tenella: A, inflorescence; B, glumes and floret; M. 
ciliata: C, glumes and floret; M. diversiglumis: D, glumes and floret. 



327 



328 FIELDIANA: BOTANY 

Petersbourg, Ser. 6, Sci. Math., Seconde Pt. Sci. Nat. 4:298. 1845. 
Figure 120. 

Delicate short-lived annual; plants sprawling, the culms 25-60 cm. long, long- 
decumbent and rooting, with erect flowering branches arising from the decumbent por- 
tions; prophylla 8-10 mm. long; culms slender, 0.5-0.7 mm. thick, hollow, thin-walled, 
glabrous; nodes retrorsely bearded; foliage glabrous to papillose-hirsute; sheaths mostly 
shorter than the internodes; ligule a rather prominent membrane, 0.7 mm. long; blades 
flat, thin, 2-6 cm. long, 1.5-2 mm. wide. Inflorescences terminal on erect branches of the 
culms, open cylindrical, 5-12 cm. long, the numerous short, slender spreading or droop- 
ing branches borne racemosely along the slender rachis, mostly directed to one side; 
basal portion of each branch forming a weak, often contorted, hispid stipe, the branches 
disarticulating from the rachis when mature; lowermost branches with several distant 
appressed spikelets, the upper ones mostly with 2 spikelets. Spikelets dimorphic; lower 
spikelets of each branch with 2 subequal minute orbicular 1-nerved glumes, ca. 0.2-0.3 
mm. long; terminal spikelet of each branch with an awned second glume, the awn from 
1-6 mm. long; lemma lanceolate, 3.5-4.2 mm. long, strongly 3-nerved, the internerves 
white, the nerves green, extending into short teeth on either side of the awn; callus 
minutely bearded; awn usually purple, flexuous, 7-10 cm. long; palea equal to the lemma 
or slightly longer, prominent, the nerves prominent, green, approaching near the nar- 
rowed tip and excurrent as minute awn-tips; anthers 3, yellow-orange, 0.4-0.6 mm. long. 

Meseta Central and Canton de Dota; Zarcero; roadsides and ditches, 
1,100-2,000 m. elevation; late November to January. Southern Mexico 
to Panama. 

Mexican specimens of this species are more robust than ours and 
have longer awns on the second glumes of the terminal spikelets. The 
plants are similar to M . tenella and M . ciliata. 

Muhlenbergia flabellata Mez, Repert. Sp. Nov. 17:213. 1921. Fig- 
ure 121. 

Perennial; plants sprawling, forming large clumps, the culms 25-45 cm. long; lower 
parts of the culms reclining and branching profusely from the lower nodes; foliage mostly 
clustered on the lower portions of the plants, the sheaths much overlapping; a single 
small leaf borne at midculm; culms thin, rigid, the interior filled with vascular bundles 
imbedded in sclerenchyma; lower sheaths becoming flattened and papery with age; ligule 
an erect pointed membrane, 2.5-8.0 mm. long, decurrent on the sheath margins; blades 
2-4 cm. long, strongly ridged and puberulent above, mostly involute. Peduncle slender, 
stiff, ridged, scabrid, up to 18 cm. long; inflorescence solitary, terminal, a slender few- 
flowered panicle, 3-9 cm. long, the branches erect; axis and branches scabrous; spikelets 
short-pedicellate, appressed to the branches. Spikelets blackish, 3-4 mm. long, excluding 
the awn; first glume ovate, blunt, 1-nerved, 1.2-1.6 mm. long; second glume oblong- 
obovate, 3-nerved, truncate or 3-lobed at the apex, the slightly scabrid nerves parallel, 
ending in the lobes; floret 3-4 mm. long; lemma lanceolate, rounded on the back, with a 
truncate callus, firm, 3-nerved; callus short-bearded; margins of lemma and lower back 
appressed-pubescent, the tip scabrid; awn stiff, scabrous, flexuous, arising from the tip 
of the lemma, 4.0-7.5 mm. long; palea equal to the lemma; anthers 3, purple, 1.8-2.1 mm. 





FIG. 121. Muhlenberffia flabellata. A, blooming plant; B, glumes; C, floret. 



330 FIELDIANA: BOTANY 

Paramos of Cerro Buena Vista (type locality); Chirripo Grande; ele- 
vations 3,300-3,500 m. Blooming sparse, but apparently yearlong. En- 
demic to Costa Rica. 

This species is listed as M. quadridentata (H.B.K.) Kunth by Hitch- 
cock in Grasses of Central America; however, that is a distinct species 
and is not found in Costa Rica. 

Muhlenbergia implicata (H.B.K.) Kunth, Rev. Gram. 1:63. 1829. 
Podosaemum implicatum H.B.K., Nov. Gen. & Sp. 1:127. 1816. 

Sprawling tufted annual plants, the culms mostly 30-50 cm. long, the lower portions 
decumbent and rooting, the numerous branches erect and bearing terminal inflores- 
cences; prophylla 10-25 mm. long; culms ca. 0.5 mm. thick, hollow, angular, the upper 
portions of the internodes minutely retrorsely puberulent; nodes dark, contracted, 
glabrous; sheaths mostly longer than the internodes but rather loose, keeled near the 
apex, glabrous; ligule a firm, pointed membrane, 2.0-3.0 mm. long; blades mostly folded, 
4-8 cm. long, 1.0-1.4 mm. wide, puberulent above. Peduncle included; inflorescences 
terminal on the main culms or on leafy branches; panicles open, delicate, ovoid, 5-15 cm. 
long, 4-8 cm. wide; spikelets long-pedicellate, the pedicels filiform, flexuous, diverging 
strongly from the branches, thickened just below the spikelet. Spikelets mostly 
purplish, 2.8-3.2 mm. long; glumes rotund, nerveless, minute, the first 0.2-0.3 mm. long, 
the second 0.4-0.5 mm. long; lemma 2.8-3.2 mm. long, narrowly lanceolate, 3-nerved, the 
lateral nerves close to the midrib, scabrous; 2 extra rows of barbs, simulating nerves, 
also present; tip of lemma bearing 2 minute slender teeth at the base of the awn; callus 
minutely bearded; awn slender, 12-20 mm. long; palea equal to the lemma; anthers 3, 
purple, 0.4-0.7 mm. long. Chromosome number n = 10 from a Costa Rican specimen. 

Dry, rocky roadsides, Meseta Central and Canton de Dota; San 
Isidro area; elevations 1,100-1,800 m.; October to April. Mexico to 
Venezuela and Colombia. 

This species is similar in general appearance to M . tenuissima, but 
differs in its larger spikelets, blunt glumes, and nonciliate lemmas. 

Muhlenbergia lehmanniana Henr., Med. Rijksherb. Leiden 40:59. 
1921. M. attenuata Swallen, Fl. Panama, Ann. Missouri Bot. Gard. 
30:138. 1943. 

Vigorous perennial, caespitose in large, dense clumps; culms arching, 70-170 cm. long, 
unbranched, 2 mm. thick, hollow, glabrous, with 3-4 nodes above the base; foliage mostly 
basal, the lower sheaths strongly keeled and densely overlapping, forming fan-shaped 
clusters, their blades often disarticulating; culm sheaths mostly longer than the inter- 
nodes; blades mostly 60 cm. or more long, 1-4 mm. wide, harsh and scabrous, folded, 
tapering to elongated threadlike points; the midrib prominently keeled. Inflorescence a 
solitary terminal panicle, usually 20-40 cm. long, oblong-ovoid, open and up to 10 cm. 
wide when the branches spread at flowering time, later dense and contracted, 2-3 cm. 
wide; color rosy or purplish when young, brownish later; spikelets appressed along the 
slender branches. Spikelets 2.5-3.0 (3.5) mm. long; glumes subequal, usually longer than 
the floret, 1-nerved, lanceolate, scabrous on the keel and usually on the surface, blunt or 
slightly bifid at the apex, usually with a minute awn tip; lemma lanceolate, 2.4-3.0 mm. 



BURGER: FLORA COSTARICENSIS 331 

long, rounded on the scabrous back, the lateral nerves slightly excurrent as minute teeth 
at the base of the awn; callus oblique, minutely bearded; awn slender, flexuous, scabrid, 
mostly 2-3 cm. long; palea equal to the lemma, glabrous between the evident nerves; 
anthers 3, purplish, 1.5-1.7 mm. long. 

Occasional on steep rocky banks and road cuts, usually in full sun; 
Meseta Central; General Valley, Boruca, Canas Gordas. November 
and December. Elevations from 400-2,000 m. Costa Rica, Panama, and 
Colombia. 

This handsome species forms colonies on steep slopes. The plants are 
conspicuous when they bloom at the beginning of the dry season. It has 
usually been included in M. emersleyi Vasey (Epicampes emersleyi 
(Vasey) Hitchc.) in older publications. 

Muhlenbergia minutissima (Steud.) Swallen was reported (as 
Sporobolus minutissimus (Steud.) Hitchc.) by Hitchcock in Gram. 
Cent. Amer. as occurring in Costa Rica. We have not found specimens 
in US or F to substantiate this report. 

Muhlenbergia nigra Hitchc., N. Amer. Fl. 17:468. 1985. 

Densely caespitose harsh perennial; plants 90-100 cm. tall, erect; culms unbranched; 
internodes up to 3 mm. thick, hollow, minutely scabrous-puberulent, finely silky below 
the nodes; nodes dark, not prominent, glabrous; sheaths mostly overlapping, smooth, 
faintly scabrous; ligules decurrent on the sheath margins, wider than the blade base, 
firm and plainly vasculated near the base, white and membranaceous toward the apex, 
7-20 mm. long, the apex pointed or lacerate; leaf blades involute, scaberulous, strongly 
ridged above, up to 25 cm. long, 2-3 mm. wide, tapering to a caudate-acuminate, scab- 
rous tip. Peduncle cylindrical, exserted up to 30 cm., scabrous, especially toward the 
apex; inflorescences terminal on the culms; panicles densely cylindrical, 10-14 cm. long, 
5-10 mm. thick, tapering to both ends, leaden gray; branches short, few-flowered, the 
spikelets borne on very short, minutely puberulent pedicels, densely overlapping and 
concealing the puberulent rachis. Spikelets narrow, 4-5 x longer than wide, 6.0-7.0 mm. 
long, strongly laterally compressed; bracts all scaberulous; glumes subequal, slightly 
longer than the floret, narrowly triangular 7:1 as folded, acuminate, 1-nerved, strongly 
keeled; floret 6.0-6.5 mm. long, ovate 6:1 as folded, acuminate or awn-tipped; 3-nerved; 
callus sparsely short-bearded; palea 2-nerved, slightly shorter than the lemma; anthers 
2.5-3.0 mm. long, whitish; caryopsis linear-cylindric, red-brown. 

This rare species was previously known only from southern Mexico 
and northern Guatemala. It occurs only at high altitudes. The only 
identifiable Costa Rican specimen is cited below. A previously col- 
lected specimen from the same site had completely smutted inflores- 
cences. The current specimen is mostly smutted, but has one normal 
inflorescence. Prov. San Jose, Valle de los Conejos, elevation ca. 3,200 
m., 5-13 November 1976, R. A. Ocampo U92 (CR, ISC). 

Muhlenbergia ramulosa (H.B.K.) Swallen, Contr. U.S. Natl. 



332 FIELDIANA: BOTANY 

Herb. 29:205. 1947. Vilfa ramulosa H.B.K., Nov. Gen & Sp. 1:137. 
1816. Sporobolus ramulosus Kunth, Rev. Gram. 1:68. 1829. Figure 
122. 

Densely tufted annual, 5-15 cm. tall; culms decumbent at the base, upper portions 
erect; branching at all nodes; prophylla 6-8 mm. long; culms less than 0.5 mm. thick, 
solid, glabrous or puberulent below the nodes; sheaths mostly longer than the inter- 
nodes, strongly ridged, glabrous; ligule a minute ciliate membrane, 0.3-0.5 mm. long; 
blades mostly folded, puberulent above, 1-2 cm. long, 0.6-0.8 mm. wide, narrowed to a 
blunt tip. Peduncle included; inflorescences numerous, terminal and axillary; terminal 
panicles 1-5 cm. long, open-cylindrical, up to 1 cm. wide; branches solitary, spreading, 
few-flowered; spikelets borne on stiff spreading pedicels about as long as the spikelet. 
Spikelets 1.0-1.2 mm. long; glumes about equal, rounded, nerveless, 0.4-0.6 mm. long; 
lemma ca. 1 mm. long, ovate, obscurely 3-nerved, blackish, glabrous, awnless; palea 
equal to lemma, convex on the back; both lemma and palea cartilaginous, smooth; palea 
occasionally with a few scattered hairs; anthers minute, ca. 0.2 mm. long, rounded. 
Many spikelets dwarfed or abortive. Chromosome number n = 10 from the Costa Rican 
specimen. 

Cultivated field, San Juan de Chicoa, Irazu, at 2,600 m. elevation. 
November. An old Jimenez specimen (1151) was from the Crater of 
Irazii, the locality probably now destroyed. Southern Mexico to Costa 
Rica. 

Muhlenbergia setarioides Fourn., Mex. PI. 2:84. 1881. M. 
polypogonoides Hack., Ann. K. K. Naturhist. Hofmus. 17:255. 1902. 
Figure 123. 

Sprawling perennial; culms up to 1 m. long, long-decumbent and rooting at the lower 
nodes; unbranched ascending flowering culms arising from the rooted portions; culms 
hollow, ca. 1.5 mm. thick, smooth and shining, glabrous; sheaths slightly keeled, gla- 
brous, shorter or longer than the internodes; leaves numerous; ligule a lacerate-ciliate 
membrane, auricled, 1.5-3.5 mm. long; blades flat, lax, dark green, 4-12 cm. long, 4-9 
mm. wide, slightly scabrid. Peduncle up to 6 cm. long; panicles terminal on the culm 
branches, 8-11 cm. long, 1.5-5 cm. wide, loosely cylindrical, interrupted below, the axis 
exposed; branches up to 3 cm. long, ascending, densely flowered to their bases; spikelets 
densely clustered on the branchlets, subsessile. Spikelets laterally compressed, 1- 
flowered, disarticulating above the glumes, 2.7-3.0 mm. long, excluding the awns; the 
bracts whitish with prominent green nerves; glumes 1-nerved, acute, keeled, lanceolate 
to narrowly ovate; first glume 1.1-1.5 mm. long, the second slightly broader, 1.5-2. 1 mm. 
long; lemma 2.2-3.0 mm. long, prominently 3-nerved, lanceolate, rounded on the back, 
the short callus oblique and minutely bearded; lemma sparsely pilose on the lower third 
of the back, scabrid on and between the nerves; awn terminal, somewhat flexuous, 5-9 
mm. long, purple; palea equal to the lemma, pilose between the keels on the lower half; 
anthers 3, 1.0-1.2 mm. long, yellow. Chromosome number n = 20 from a Costa Rican 
specimen. 

Rare, moist shaded roadbanks, eastern Meseta Central, Irazu and 
Barba; elevations from 1,500 to 2,100 m.; blooming in February. Ver- 
acruz, Mexico; Guatemala and El Salvador; Costa Rica and Panama. 






FIG. 122. Muhlenbergia species. Af. ramulosa: A, blooming plant; B, spikelet; Af. 
calcicola: C, blooming plant; D, spikelet. 




FIG. 123. Muhlenbergia setarioides. A, decumbent base of plant; B, panicle; C, 
spikelet; D, floret. 



334 



BURGER: FLORA COSTARICENSIS 335 

This species is in many ways similar to the rhizomatous mesophytic 
species of this genus common in temperate climates, such as M. 
schreberi and M. frondosa. It has no close relatives in Central 
America. 

Muhlenbergia tenella (H.B.K.) Trin., Gram. Unifl. 192. 1824. 
Podosaemum tenellum H.B.K., Nov. Gen. & Sp. 1:128. 1816. 
Trichochloa tenella (H.B.K.), Roem. & Schult., Syst. Veg. 2:385. 
1817. Trinius refers only to the Roemer & Schultes name, which is 
based in turn on P. tenellum H.B.K. Figure 120. 

Short-lived annual; plants in small tufts, the culms erect or more commonly sprawling, 
15-35 cm. long, branching freely from the lower and middle nodes; prophylla 8-10 mm. 
long; culms 0.2-0.3 mm. thick, hollow, glabrous; nodes glabrous; leaf sheaths shorter 
than the internodes, glabrous or sometimes hirsute, especially near the apex; ligule a 
minute lacerate membrane, ca. 0.3 mm. long; leaf blades flat, 2.0-3.5 cm. long, 0.8-2.0 
mm. wide, from nearly glabrous to appressed-hirsute on one or both surfaces. Peduncle 
mostly included in the upper sheath; inflorescences numerous, terminal on the main 
culms or on leafy branches; panicle slender, 3-7 cm. long, the branches solitary, ap- 
pressed to the rachis, bearing spikelets to their bases; pedicels from very short to as long 
as the spikelets, appressed to the branches. Spikelets overlapping, 2.2-2.7 mm. long; 
first glume 0.6-1.2 mm. long, 1-nerved, lanceolate, acuminate or short-awned; second 
glume similar, 0.9-1.7 mm. long; lemma narrowly lanceolate, 1.8-2.7 mm. long; nerves 
prominent, green; internerves white in immature spikelets; callus minutely bearded; 
awn terminal, 15-25 mm. long, thin, flexuous; palea equal to the lemma; anthers 3, 
yellow, 0.3-0.4 mm. long. Chromosome number n = 10 from Costa Rican specimens. 

Moist cliffs and rocky banks, especially in stream valleys, road cuts; 
Meseta Central to Guanacaste; Valley of Rio Pacuare on the Caribbean 
slope; elevations from 50 to 1,200 m. October to mid-January. Mexico 
to Panama. 

This delicate little annual grass begins to grow during the rainy 
season, but remains vegetative for a long time. The onset of blooming 
is simultaneous over large areas, suggesting that blooming is con- 
ditioned by photoperiod. All of the species of this annual group (M . 
ciliata, M. diversiglumis, M. implicata, M. tenella, and M . tenuis- 
sima) are very similar and may not all merit specific recognition. Some 
of our specimens of M. tenella exhibit large pyriform swellings at some 
of the lower nodes, each containing an insect grub. 

Muhlenbergia tenuissima (Presl) Kunth, Rev. Gram. 1, Suppl. 
XVI. 1830. Podosaemum tenuissimum Presl, Rel. Haenk. 1:230. 
1830. Muhlenbergia nebulosa Scribn., Beal, Gr. N. Amer. 2:247. 1896. 

Delicate, short-lived annual; culms sprawling, 7-30 cm. long, much branched, the 
internodes slender, hollow, thick-walled, dull, scabrid below the puberulent nodes; leaf 
sheaths shorter than the internodes, puberulent or glabrous; ligule a thin membrane, 



336 FIELDIANA: BOTANY 

0.8-1.2 mm. long; blades mostly folded, puberulent above, 3-7 cm. long, 0.5-1.0 mm. 
wide. Peduncle included or exserted up to 3 cm. Inflorescences numerous, terminal on 
the culm and leafy branches; panicles 4-8 cm. long, open cylindrical, 1-2 cm. wide; 
branches delicate, filiform, the spikelets long-pedicellate on stiff filiform pedicels which 
diverge strongly from the branches and are thickened just below the spikelets. Spikelets 
1.7-1.9 mm. long; glumes ovate-acuminate, 1-nerved, rarely awn-tipped, the first 0.5-0.7 
mm. long, the second similar, 0.8-1.0 mm. long; lemma narrowly lanceolate, 3-nerved, 
1.7-1.9 mm. long, ciliate on the margins, the callus not bearded; awn thin, 6-11 mm. long; 
palea equal to the lemma, ciliate on the keels; anthers 3, purple, 0.5-0.6 mm. long. 

Savannas of Guanacaste, near the CIA, Liberia and Las Animas; 
elevations 100-200 m. December. Southwestern Mexico; Honduras; 
Costa Rica and Panama. 

This delicate little grass resembles M. implicata, but differs in the 
ciliate lemmas, pointed glumes, and smaller spikelets. 

NASSELLA Desvaux 

Perennial grasses; caespitose; culms branching below; inflorescence a terminal panicle. 
Spikelets 1-flowered, disarticulating above the equal, elongated glumes; lemma ovoid or 
obovoid, round in cross-section, rigid, the edges overlapping and concealing a short, 
flattened palea; callus short, oblique, bearded; apex of lemma with a blunt beak at the 
overlap; awn often eccentrically inserted, geniculate, the basal segment twisted, readily 
deciduous from the body of the lemma. 

This genus is very closely allied to Stipa and is sometimes regarded 
as a section of that genus. It differs in the readily deciduous awn that is 
often eccentrically attached and in microscopic characters of the an- 
thoecium. (Pooideae: Stipeae.) 

Nassella linearifolia (Fourn.) Pohl, comb. nov. Stipa linearifolia 
Fourn., Mex. PI. 2:73. 1881. Oryzopsis fiorentula Pilger, Bot. Jahrb. 
Syst. 27:26. 1899. Stipa florentula (Pilger) Parodi, Revista Mus. La 
Plata, Secc. Bot. 6:228. 1944. Figure 207. 

Perennial, in dense clumps; culms erect, freely branching from the lower nodes, the 
branches mostly short, erect, and very leafy; culms slender, hollow, glabrous; nodes 
prominent, glabrous, yellowish; sheaths glabrous, firm; ligule a white membrane, 0.5 
mm. long; blades stiff, strongly ridged above, involute, 5-17 cm. long, 2-3 mm. wide, 
glabrous, with a few short auricular hairs. Peduncle 6-12 cm. long, thin, stiff, wiry, 
glabrous; panicles solitary on the culm or on erect leafy branches, 8-17 cm. long, ovoid, 
open, the branches paired, naked below, the longest 4-6 cm. long; spikelets appressed 
along the outer half or third of each branch. Spikelets terete; glumes equal, 4.2-5.0 mm. 
long, longer than the floret, narrowly ovate, acuminate, rounded on the back, 3-nerved, 
often purplish, connivent until the floret is shed, then spreading; lemma narrowly 
obovate-cylindrical, somewhat quadrate; apex obliquely truncate, 2.8-3.0 mm. long, 
surface brown, minutely roughened, the body appressed-pubescent with white hairs, the 
short callus white-bearded; margins strongly overlapping and concealing an oblong 



BURGER: FLORA COSTARICENSIS 337 

membranaceous palea ca. 1 mm. long; awn readily deciduous, 13-15 mm. long, twice 
geniculate, the lower segment tightly twisted, the second segment less so, both minutely 
pubescent; floret apparently never opening, the flower cleistogamous; lodicules 3, flat; 
anther 1, ca. 0.5 mm. long, placed between the stigmas. 

Collected once in Costa Rica, from a gully 1 km. below San Juan de 
Chicoa, elevation 2,600 m. Blooming in November. Southern Mexico; 
Guatemala; Costa Rica; Colombia and Bolivia. 

Recent studies of the anatomy of the anthoecia of fossil and living 
Stipeae by Thomasson indicate that the epidermis of the lemmas of this 
species is much more similar to that of species ofNassella than it is to 
that of typical species of Stipa. This difference is supported by the 
deciduous nature of the awn and the plump, somewhat flattened floret. 

OLYRA Linnaeus 

Caespitose perennial grasses, the culms usually elongated, often thick and hardened; 
leaf blades with short pseudopetioles, often oblique-based; plants monoecious. Inflores- 
cence a panicle, usually bearing pistillate spikelets toward the tips of the branches and 
staminate ones near the bases. Pistillate spikelets: Glumes equal, several-many-nerved; 
floret single, disarticulating above the glumes (except in O. lateralis); lemma rigid, 
bony, obtuse, its margins usually inrolled over the edges of a palea of similar texture. 
Staminate spikelets: Soft-textured; glumes absent; floret 1, disarticulating from the 
pedicel; lemma 3-nerved, keeled; palea 2-keeled, equal to the lemma; anthers 3. 

The plants are somewhat bamboo-like in general aspect, but usually 
have foliage leaves on the main stem as well as on the branches. They 
usually bloom annually, in contrast to the woody bamboos, which 
bloom very irregularly or at long intervals. The leaf anatomy and the 
possession of pseudopetioles indicate that the genus is bambusoid, 
although in older systems, it was placed in the tribe Paniceae. In such 
treatments, the pistillate spikelets were described as missing a first 
glume and possessing only a second glume and a sterile lemma below 
the floret. (Bambusoideae: Olyreae.) 

KEY TO SPECIES OF Olyra 

la. Tall, erect, or scrambling plants; leaf blades 12-22 cm. long, 1.5-8.5 cm. wide . . 2 
Ib. Weak trailing plants; leaf blades 3.5 cm. or less long, 5-10 mm. wide 

O. lateralis 

2a. Sheath auricles spreading, purple, forming horizontal collar around the culm; 
leaf blades with triangular purple zone at base of nearly symmetrical blade 

O. standleyi 

2b. Sheath auricles erect, inconspicuous, not spreading; leaf blades very oblique- 
based, not purple-marked at base O. latifolia 

Olyra lateralis (Presl) Chase, Proc. Biol. Soc. Wash. 21:179. 1908. 



338 FIELDIANA: BOTANY 

Panicum laterale Nees, Agrost. Bras. 213-214. 1829, var. a. 0. sar- 
mentosa Doell, Mart. Fl. Bras. 2:819. 1877. Figure 124. 

Sprawling perennial, the culms up to 4 m. long, branching freely, trailing over banks 
and low vegetation; internodes 1.0-1.5 mm. thick, hollow, thin-walled, glabrous or pu- 
berulent below the nodes; nodes prominent, with 2 circular ridges and a groove between 
them, retrorsely puberulent; leaf sheaths shorter than the internodes, appressed-pu- 
berulent especially toward the apex; ligule a short membrane, 0.2-0.5 mm. long; 
pseudopetiole puberulent, 0.7-1.0 mm. long; blades flat, rather stiff, narrowly triangular 
3-5:1, cordate-based, 1.5-4.0 cm. long, 5-13 mm. wide, sparsely puberulent or scabrid, 
the margins sometimes ciliate, tapering abruptly to a rather rounded tip; underside 
glaucous. Inflorescences paniculate, terminal on the culm and also axillary from the 
upper leaf sheaths, 2-4 cm. long, open-pyramidal, to 3 cm. wide, few-flowered. Pistillate 
spikelets: Few, at branch tips; dorsally compressed, 2.4-3.0 mm. long, the length 2.0-2.8 
x the width; disarticulation below the equal glumes that completely cover the floret; first 
glume 5-nerved, stiff, minutely woolly; second glume similar, 3-nerved; floret ovate 3:2, 
1.4-1.5 mm. long; lemma rigid; stramineous, striate, with a basal areole; margins thick 
but not conspicuously inrolled; palea 1.2 mm. long; lodicules 3; style 1; stigmas 3; cary op- 
sis elliptical 3:2, reddish brown, with a persistent style. Staminate spikelets: Borne on 
lower portions of the branches, 3-4 mm. long, ovate 4.5:1, acute; glumes subequal, 
3-4-nerved; anthers 3, purple, 2.0-2.3 mm. long. 

This species is rare in Costa Rica, and only one specimen has been 
collected in the twentieth century. Puntarenas, Cienaga de Agua 
Buena, Canas Gordas, Pittier 11008; February 1897, Helechales del 
General, vallee du Diquis, 700 m., 3 February 1898, Pittier 12058; 
Cordoncillal, Pittier 3641; San Jose, Vicinity of El General, Skutch 
2254- Peru and Bolivia to Venezuela, Colombia, Panama, and Southern 
Costa Rica. 

Olyra latifolia L., Syst. Nat. ed 10, 2:1261. 1759. Figure 125. 

Caespitose perennial, the plants forming clumps of up to 20 culms from a hard, knotty 
crown; culms up to 6 m. long, erect, arching, scrambling in brush and trees, or decum- 
bent; branching abundant from middle and upper nodes; internodes up to 1 cm. thick, 
hollow, thick-walled; internodes usually glabrous or, exceptionally, pubescent near the 
apex, often purplish-spotted; lower sheaths deciduous, those of the branches usually 
persistent and overlapping, glabrous to hispid and puberulent, the overlapping edge 
ciliate; apex of sheath prolonged into an auricle; ligule a thick membrane, up to 4 mm. 
long; pseudopetiole 1-3 mm. long, puberulent to heavily bearded; leaf blades flat, oval 3-7 
x longer than wide, very oblique, one side of the blade narrow and the other wide at the 
base, these dimensions reversed toward the apex of the blade; apex rather abruptly 
short-caudate; length 8-22 cm.; width 1.5-8.5 cm.; upper surface usually glabrous, lower 
surface velvety or glabrous. Inflorescences paniculate, numerous at the apex of the culm 
and the tips of leafy branches, ovoid or pyramidal, up to 18 cm. long and about a third as 
wide, open to rather congested. Spikelets unisexual, the pistillate ones usually solitary 
at the tips of the branches, sometimes several on a branch; pistillate spikelets more 
abundant toward the apex of the panicle, the staminate ones toward the base of the 
panicle and on lower parts of the branches. Peduncle, rachis, and branches scabrous to 
softly hirsute. Staminate spikelets: Borne on appressed pedicels 1-3 x as long as the 




FIG. 124. Olyra lateralis. A, blooming plant; B, leaf blade base, showing 
pseudopetiole; C, two views of a pistillate spikelet; D, pistillate floret within a glume; E, 
pistillate floret. 



339 




FIG. 125. Olyra latifolia. Blooming plant, pistillate spikelet, floret, staminate 
spikelet. 



340 



BURGER: FLORA COSTARICENSIS 341 

spikelet; membranaceous, ca. 5 mm. long, ovate 6:1, acute; glumes absent; lemma 
keeled, 3-nerved, bearing a straight awn up to 4 mm. long; palea of equal length, 
2-nerved; lodicules 3, truncate, vasculated, bearing 2-3-celled microhairs at the tip; 
anthers 3, 2.7-3.5 mm. long, brown. Pistillate spikelets: Borne on flattened, thickened 
pedicels at the tips of branches, or several in a series along a branch, dorsally com- 
pressed, 8-15 mm. long, not including the awns; glumes usually glabrous, rarely pu- 
berulent; first glume ovate, caudate, tapering gradually into a thick awn up to 20 mm. 
long; nerves 7-9; second glume similar but with a shorter awn, 5-7-nerved; floret readily 
deciduous; lemma 4.8-5.2 mm. long, elliptical 1.5-2:1, glabrous, rigid, blunt, white, 
shiny, rounded on the back, with an evident basal germination lid; margins distinctly 
inrolled over the edges of a rigid convex palea of similar color and texture, 3.7-4.0 mm. 
long; lodicules truncate, vasculated; caryopsis filling the cavity of the floret, with a stiff 
brown pericarp; endosperm opalescent, white, horny. Chromosome number n = 11, 22 
from Costa Rican and Venezuelan material. 

Common in forests and forest margins, at elevations up to 850 m., on 
both Pacific and Caribbean slopes. New growth is initiated during the 
rainy season, and the primary panicles bloom then. The development 
of smaller panicles on the lateral branches, however, prolongs the 
blooming season throughout the year. Mexico to Brazil, Bolivia, and 
northern Argentina; West Indies; introduced in Africa. This species is 
somewhat weedy and thrives in the disturbed margins of forests. It is 
amazingly variable in stature, leaf size and shape, and pubescence. 

Olyra stand ley i Hitchc., Proc. Biol. Soc. Wash. 40:87. 1927. 

Perennial from hard crowns, the new buds at the base covered with shining overlap- 
ping scales; plants 2-3 m. tall, the culms arching, branching from the middle nodes, the 
branches solitary; prophyllum inserted above the node, to 6 cm. long, ciliate on the keels; 
internodes to 3 mm. thick, glabrous, thick-walled; nodes conspicuous, with a swollen 
purplish band overlapped above by the base of the sheath, glabrous or retrorsely pu- 
berulent; sheaths glabrous to sparsely retrorsely papillose-hispid; lower sheaths shorter 
than the internodes, the upper longer and overlapping; sheath auricles present, purple, 
spreading horizontally and forming a sort of collar around the culm, the margins hispid- 
ciliate; ligule inconspicuous, a stiff purple membrane ca. 1 mm. long; pseudopetiole ca. 2 
mm. long, pubescent; leaf blades flat, glabrous, ovate 4-5:1, nearly symmetrical, 12-24 
cm. long, 2.5-5.0 cm. wide, the base cordate, with a conspicuous deltoid purple area at 
the midrib; surfaces glabrous, the upper dark green, the lower glaucous. Inflorescences 
terminal on leafy branches; panicle to 15 cm. long and about as wide, open, pyramidal, 
with successive whorls of stiff ascending branches, the longest 11 cm. long. Staminate 
spikelets: Numerous, appressed along the lower parts of the panicle branches, short- 
pedicellate, ca. 1 cm. long; glumes absent; lemma acuminate; palea about equal to the 
lemma. Pistillate spikelets: 1-10 borne at branch tips, on thickened pedicels; first glume 
ca. 2 cm. long, including the awn, 5-nerved, glabrous; second glume slightly shorter, 
5-nerved; floret 8 mm. long, obtuse, the surface of the lemma minutely pitted, its mar- 
gins inrolled over the edges of the palea. 

The type specimen, which is fruiting, was collected at El Muneco by 
Standley and Torres in March 1926 (50982). We have collected vegeta- 
tive material from what is apparently the same stand, on the road S of 



342 FIELDIANA: BOTANY 

El Muneco. The plants are conspicuous because of the large size of the 
leaf blades and are readily identifiable by the purple auricular collar at 
the apex of the sheath and the purple triangle at the base of the leaf 
blades. The only other Costa Rican collection is the following: Prov. de 
Cartago, Moravia de Chirripo, 8 km. camino el Rio Chirripo, altitude 
1,400 m., January 1976, R. Ocampo 1212. This specimen, like recent 
material from El Muneco, is vegetative. The distance between these 
two localities is over 25 km. , indicating that the species may probably 
be found in other intermediate sites. Recent collections from Cerro 
Jefe, Panama, by Calderon, may be the same species. No other collec- 
tions are known. 

OPLISMENUS Beauvois 

REFERENCE: A. S. Hitchcock, The North American species of Op- 
lismenus, Contr. U.S. Natl. Herb. 22:123-132. 1920. 

Creeping grasses, the lower portions of the culms decumbent and rooting; blooming 
from ascending leafy branches. Duration indefinite, the plants forming large patches by 
vegetative spread. Inflorescence a slender terminal panicle of short, spikelike racemes; 
spikelets paired, very short-pedicellate, the pairs borne alternately in 2 rows along the 2 
lower sides of the triquetrous rachis of the racemes. Spikelets disarticulating below the 
glumes, more or less laterally compressed; glumes keeled, subequal, membranaceous, 
shorter than the spikelet, awned from a bifid tip, the first usually 3-nerved, the second 
5-nerved; lower (sterile) lemma 5-9-nerved, awn-tipped or awnless, without a flower or 
palea, enfolding the fertile floret; upper (fertile) floret shorter than the sterile lemma and 
concealed by it; lemma dorsally compressed, narrowly ovate, acute, coriaceous, shining, 
longitudinally finely striate, the margins incurved, flat, overlapping the edges of the 
equal, slightly convex palea; lodicules 2, truncate; anthers 3; style branches separate, 
naked at the base. 

A small genus of 10-15 species, occurring in the subtropics and 
tropics of both Old and New Worlds. The plants appear similar to 
Pseitdechinolaena in growth habit and to Echinochloa in spikelet 
structure. (Panicoideae: Paniceae.) 

KEY TO SPECIES OF Oplismenus 

la. Awns upwardly scabrous; racemes conspicuously whitish, hispid; glumes and sterile 

lemma longitudinally ridged 0. burmannii 

Ib. Awns smooth; racemes not hispid; glumes and sterile lemma not ridged 2 

2a. Racemes very short, appearing wider than long, the rachis 2-6 mm. long; 

spikelets usually 7 or fewer per raceme O. setarius 

2b. Racemes longer than wide, the rachis of lower racemes 1 cm. or more long, 
bearing numerous spikelets O. hirtellus 

Oplismenus burmannii Beauv., Ess. Nouv. Agrost. 54. 1812. Fig- 
ure 126. 




FIG. 126. Oplismenus species. 0. burmannii: A, inflorescence; B, spikelet; 0. hirtel- 
lus: C, spikelet. 



343 



344 FIELDIANA: BOTANY 

Duration indefinite, probably annual; plants decumbent, forming large patches, the 
culms long-decumbent and rooting from the nodes, branching freely, the branches 
spreading or ascending, 10-30 (50) cm. long, mostly leafy only on the lower half, the 
naked peduncle comprising more than half of the length; internodes ca. 1 mm. thick, 
pubescent in a single villous line below the overlapping edge of the sheath above, some- 
times also papillose-hispid all over; sheaths shorter than the internodes, densely short- 
ciliate on the overlapping margin, more or less papillose-hispid as well; ligule a thin 
ciliate membrane, in total 0.7-1.2 mm. long; leaf blades flat, ovate, 3-4:1, 2-5 cm. long, 
9-15 mm. wide, scabrous, puberulent, hirsute, or papillose-hispid. Peduncle 3-18 cm. 
long, slender, bearded at the apex; inflorescence rather dense, 3-6 cm. long, the 3-7 
ascending racemes overlapping; axis and the rachises of the racemes densely papillose- 
hispid; spikelets paired, subsessile on the lower 2 sides of the triquetrous rachis, often 
one of the pair reduced or obsolete. Spikelets whitish, conspicuously hispid, 2.8-3.7 mm. 
long; first glume narrowly ovate, 2.0-2.7 mm. long, 3-nerved, notched at the apex, the 
purplish antrorsely scabrous awn 5-10 mm. long, attached at the notch; second glume 
ovate, 5-nerved, the awn 2.5-5 mm. long; lower (sterile) lemma 2.6-3.5 mm. long, ellipti- 
cal, 7-9-nerved, heavily hispid-bearded in a wide band across the middle, pubescent 
below the apex on the inner side; palea and flower lacking; upper (fertile) floret 1.9-2.1 
mm. long, ovate 3:1, acute, coriaceous, shining, striate; palea equal; lodicules 2, trun- 
cate; anthers 3, orange, 1 mm. long; stigmas purple. Chromosome numbern = 18 from a 
Costa Rican specimen. 

Open dry areas and open shade, roadsides, pastures, stream banks; 
sea level to 1,900 m. elevation, most common at lower elevations on the 
Pacific slope, apparently uncommon on the Caribbean slope. October 
to May. Southern Mexico to northern South America and the Carib- 
bean Islands. Introduced from Asia. 

The binomial 0. burmannii is usually stated to have been based 
uponPamc^m burmannii Retz., Obs. Bot. 3:10, 1783. Beauvois, how- 
ever, makes no reference to the Retzius name. 

Oplismenushirtellus(L.) Beauv., Ess. Nouv. Agrost. 54:168. 1812. 
Panicum hirtellum L., Syst. Nat. ed. 10. 2:870. 1759. Figure 126. 

Duration indefinite; culms 59-90 cm. long, the bases long-decumbent and rooting from 
the nodes, forming large patches, the rooted portions branching freely; internodes 1 mm. 
thick, hollow, glabrous or pubescent below the nodes; prophylla broad, up to 1.6 cm. 
long; nodes glabrous or bearded; sheaths shorter than the internodes, glabrous, pilose, 
or papillose-hispid, their exposed margins softly ciliate; ligule a ciliate membrane, 
0.6-1.2 mm. long; blades flat, thin, lanceolate 4.5-7.5:1, 4-12 cm. long, 7-20 mm. wide, 
somewhat asymmetric; surfaces glabrous, scabrous, velvety-pubescent, or with a few 
papillose-hispid bristles at the base. Inflorescences terminal on leafy, ascending or erect 
branches; peduncles slender, exserted 1.5-12 cm., glabrous or appressed-pilose; inflores- 
cence 7-14 cm. long, composed of 3-7 spikelike 1-sided racemes, arranged racemosely 
along the central rachis; racemes 1-3 cm. long, the rachis glabrous, pilose, or papillose- 
hispid; spikelets compactly arranged, in pairs, these attached alternately in 2 rows on 
the 2 lower sides of the triquetrous rachis; 1 spikelet of some pairs reduced or abortive; 
pedicels very short. Spikelets laterally compressed, 3.0-4.0 mm. long; glumes keeled, 
the first 1.8-2.5 mm. long, ovate, 3-5-nerved, bearing a smooth, stiff awn 4-10 mm. long, 
attached just below the summit; second glume 2.0-2.7 mm. long, ovate, 5-7-nerved, with 



BURGER: FLORA COSTARICENSIS 345 

a short awn 2-4 mm. long, attached just below the summit; lower (sterile) lemma 3.0-3.5 
mm. long, ovate, 5-9-nerved, lacking palea or flower, glumes and sterile lemma glabrous, 
scabrous, or papillose-hirsute; upper (fertile) floret dorsally compressed, 2.5-3.0 mm. 
long, elliptical 3:2; lemma faintly 5-nerved, shiny, striate, coriaceous, acute, the thin 
margins covering the margins of the broad palea of equal length; lodicules 2, truncate; 
anthers 3, yellow-orange, 1.5-1.7 mm. long; caryopsis elliptical 8:3, white. 

Usually in shade of brush or open forests, roadsides; sea level to 
2,000 m. elevation. Meseta Central, Canton de Dota, Turrialba, 
Pejivalle, General Valley, Limon area, Tilaran, Hda. Inocentes. May 
to February, probably yearlong. Mexico to Argentina; Caribbean Is- 
lands. 

This rather weedy species is amazingly variable in the pubescence of 
leaves, sheaths, and rachis of the spikes; however, all of our chromo- 
some counts from Costa Rica and Venezuela indicate a single number, 
rc = 45. 

Oplismenus setarius (Lam.) Roem. & Schult., Syst. Veg. 2:481. 
1817. Panicum setarium Lam., Tabl. Encycl. 1:170. 1791. 

Duration indefinite; culms long-decumbent, rooting at the nodes; erect portions 20-30 
on. long; internodes 1 mm. thick, hollow, glabrous or pilose with scattered hairs, espe- 
cially in a line below the margins of the leaf sheath above; nodes bearded or glabrous; 
sheaths shorter than the internodes, more or less papillose-pilose or hispid, especially 
toward the apex; margins ciliate; ligule a thin membrane, ciliate at the apex, ca. 1.5 mm. 
long; leaf blades 3-5 cm. long, 4-14 mm. wide, appressed-pilose or with scattered 
papillose-hispid hairs. Inflorescences terminal on leafy erect branches; peduncle slender, 
exserted 1-11 cm.; panicle 4-9 cm. long, made up of 4-7 short racemes borne singly at the 
nodes of the rachis; individual racemes very short, the rachis 2-6 mm. long, puberulent, 
bearing 7 or fewer spikelets, in pairs along the lower sides of the triquetrous rachis; one 
member of a pair often reduced or abortive. Spikelets more or less laterally compressed, 
2.7-3.3 mm. long; first glume 1.7-2.2 mm. long, 3-5-nerved, ovate, rounded or tapered to 
the tip; awn smooth, 4-5 mm. long, inserted just below the tip; second glume 1.8-2.3 mm. 
long, 5-nerved, ovate; awn 1.5-2 mm. long; lower (sterile) lemma 2.4-3.0 mm. long, 
ovate, broad, partially enveloping the fertile floret, 5-7-nerved; awn very short or lack- 
ing; palea and flower absent; upper (fertile) floret 2.3-2.7 mm. long, the lemma elliptical, 
acute, 2.5-3.5:1, cartilaginous, shining, longitudinally striate; palea of equal length, 
similar; lodicules 2, truncate; anthers 3, 1.3 mm. long, orange. 

Rare or overlooked; shaded roadsides and cafetales; Meseta Central, 
Turrialba, 1,000-1,700 m. August to December. Southeastern United 
States to Guatemala and Honduras; West Indies; northern South 
America to Paraguay. 

ORTHOCLADA Beauvois 

Leaf blades borne on prominent pseudopetioles; blades conspicuously cross-veined; 
plants bearing numerous hook-shaped microhairs. Inflorescence a large panicle. 
Spikelets 2-flowered, laterally compressed and keeled, disarticulating below the glumes 



346 FIELDIANA: BOTANY 

and below the second floret; glumes subequal, the first 3-nerved, the second 5-nerved; 
lemmas 5-7-nerved, acuminate or awn-tipped; rachilla slender, elongate, held by the 
keels of the palea. 

The genus has one species in tropical America and a second in 
Africa. It belongs to the Centosteceae, a tribe of uncertain relation- 
ships, probably close to the bamboos. 

Orthoclada laxa (L. Rich.) Beauv., Ess. Nouv. Agrost. 70, 149, 
168. 1812. Aira laxa L. Rich., Actes Soc. Hist. Nat. Paris 1:106. 1792. 
Figure 127. 

Perennial; caespitose; culms erect or decumbent and rooting at the basal nodes, un- 
branched, glabrous or slightly puberulent below the nodes; plants mostly 50-120 cm. tall, 
the panicle making up ca. hah the total; leaf sheaths 5-15 cm. long, mostly overlapping, 
slightly keeled above, densely covered with uncinate microhairs and a few long slender 
trichomes; sheath auricles prominent, erect; ligule a thickish lacerate-ciliolate membrane 
less than 1 mm. long; leaf blades borne on pseudopetioles 0.5-4.0 cm. long; blades nar- 
rowly ovate, the larger ones 10-20 cm. long, 17-35 mm. wide. Inflorescence a large open, 
dome-shaped terminal panicle; peduncle included or exserted up to 25 cm., bearing 
uncinate microhairs; panicle up to 35 cm. long and about as wide, extremely open, the 
slender branches bearing a few spikelets near their tips; rachis short, usually 4-10 cm. 
long, abruptly terminating in an acicular bract up to 3 cm. long; major branches up to 25 
cm. long, very slender; spikelets borne in small groups near the branch tips and ap- 
pressed to them. Spikelets 8-10 mm. long, laterally compressed and keeled, disar- 
ticulating below the glumes, the second floret also disarticulating; first glume 3.5-4.5 
mm. long, lanceolate, 3-nerved; second glume 4-5 mm. long, narrowly ovate, 5-nerved; 
florets 2, equal, 5-6 mm. long, ovate, acute or awn-tipped, scabrid on upper parts; palea 
prominent, nearly as long as the lemma, scabrid on the keels near its tip, grasping the 
slender rachilla by its keels; rachilla 2-3 mm. long, the ultimate segment usually bearing 
a rudimentary third floret up to 3 mm. long. Chromosome number n = 12. 

Common in wet forests, forest margins, and cacao groves; elevations 
below 550 m. near both Atlantic and Pacific coasts, Provinces of 
Heredia, Limon, and Puntarenas; somewhat weedy; apparently 
blooming yearlong. Southern Mexico to northern South America. 

ORYZA Linnaeus 

REFERENCES: D. Chatterjee, A modified key and enumeration of the 
species ofOryza L., Indian J. Agric. Sci. 18:185-192. 1948. T. Tateoka, 
Taxonomic studies of Oryza, I. The 0. latifolia complex, Bot. Mag. 
(Tokyo) 75:418-427. 1962. 

Aquatic or paludose grasses; inflorescence a terminal panicle. Spikelets 1-flowered, 
strongly laterally compressed and keeled; glumes reduced to minute ridges or a cupule at 
the tip of the pedicel; spikelet with 2 reduced sterile lemmas at the base, the fertile floret 
terminal, all 3 florets disarticulating from the cupule as a unit; lemma 5-nerved, coriace- 
ous, apiculate or awned, the involute margins clasping the marginal ridges of the palea; 
palea keeled, 3-nerved, similar to the lemma, apiculate; stamens 6. 




FIG. 127. Orthoclada laxa. Blooming plant. 



347 



348 FIELDIANA: BOTANY 

Several interpretations of the spikelet of Oryza have been made. 
Some authors consider the sterile lemmas as glumes. The fertile floret 
has also been interpreted as the result of the fusion of two florets, the 
lower one contributing a lemma and a flower having 3 anthers and a 
pistil, the upper contributing a lemma and 3 anthers. Species 23, 
mostly in the tropics of the Old World. The genus is closely related to 
Leersia, differing in the well-developed lower sterile lemmas. 
(Oryzoideae: Oryzeae.) 

KEY TO SPECIES OF Oryza 

la. Spikelets readily deciduous; ligules 3-6 mm. long; wild plants O. latifolia 

Ib. Spikelets persistent on pedicel; ligules at least 10 mm. long; cultivated crop 

O. saliva 

Oryza latifolia Desv., J. Bot. Desv. II. 1:77. 1813. 

Caespitose perennial, rather succulent, in small tufts; culms erect, to 2 m. tall, usually 
simple, hollow, thin-walled, 5-10 mm. thick, glabrous; nodes glabrous, shrunken; sheaths 
mostly longer than the internodes and overlapping, glabrous; ligule a stiff membrane, 3-6 
mm. long, ciliate at the apex and pubescent on the back; blades of larger plants up to 55 
cm. long, 35 mm. wide, usually glabrous, rarely hirsute, scabrous on margins and sur- 
faces; lower leaves with prominent ciliate blade auricles, the upper ones somewhat 
pseudopetiolate, the pseudopetiole hirsute, the blades tapering to a narrow base. Panicle 
open, many-flowered, up to 40 cm. long and 20 cm. wide; lower branches verticillate, up 
to 30 cm. long, with a tuft of short hairs at the bases, the basal portions naked, the 
secondary branches and spikelets appressed. Spikelets short-pedicellate along the 
branches, 6-7 mm. long; glumes reduced to 2 minute excrescences at the tip of the 
pedicel; sterile lemmas awl-shaped, 1-nerved, the first 1-2 mm. long, the second 1.5-2.0 
mm.; lemma 5.5-7.0 mm. long, 2.0-2.5 mm. wide, elliptic-oblong, apiculate or with an 
awn up to 3.5 cm. long, rugose, hispid-ciliate on the margins, nerves, and sometimes the 
internerves; palea oblong, apiculate, much narrower than the lemma, the pubescence as 
on the lemma; anthers 6, 2-3 mm. long, yellow. Chromosome number n = 24 from Costa 
Rican material. 

Occasional, wet muddy banks, marshes, wet pastures, forest open- 
ings; low elevations, 5-300 m.; both Caribbean and Pacific slopes. April 
to October, probably yearlong. Southern Mexico and the Caribbean 
Islands to Brazil and Paraguay. 

Oryza sativa L., Sp. PI. 333. 1753. Figure 128. 

This is the common cultivated rice, widely cultivated at low eleva- 
tions in Costa Rica. There are a myriad of cultivated strains, differing 
mostly in agronomic characteristics. The spikelets may be awned or 
awnless. As in all cultivated cereals, the spikelets are retained on the 
plant past maturity, allowing efficient harvesting. Common names: 
Arroz, "rice." 




FIG. 128. Oryza saliva. Culm base, inflorescence, spikelet. 



350 FIELDIANA: BOTANY 

PANICUM Linnaeus 

REFERENCES: S. T. Blake, New criteria for distinguishing genera 
allied to Panicum (Gramineae), Proc. Roy. Soc. Queensland 70:15-19. 
1958. Agnes Chase, Notes on genera of Paniceae IV, Proc. Biol. Soc. 
Wash. 24:103-160. 1911. R. W. Freckmann, Taxonomic studies in 
Panicum subgenus Dichanthelium, Unpubl. Ph.D. Diss., I.S.U. Li- 
brary. 175 pp. 1967. F. W. Gould, Nomenclatural changes in the 
Poaceae, Brittonia 26:59-60. 1974. A. S. Hitchcock & Agnes Chase, 
The North American species of Panicum, Contr. U.S. Natl. Herb. 
15:1-396. 1910; and Tropical North American species of Panicum, 
Contr. U.S. Natl. Herb. 17:459-539 + XII. 1915. Chien-Chang Hsu, 
The classification of Panicum (Gramineae) and its allies with special 
reference to the characters of lodicule, style-base and lemma, J. Fac. 
Sci. Univ. Tokyo, Sect. 3, Bot. 9:3:43-150. 1965. M. G. LeLong, 
Studies of reproduction and variation in some Panicum subgenus 
Dichanthelium, Unpubl. Ph.D. Diss., I.S.U. Library. 228pp. 1965. L. 
R. Parodi, Estudios sistematicos sobre las Gramineae-Paniceae argen- 
tinas y uruguayas, Darwiniana 15:65-111. 1969. 

Plants annual or perennial, caespitose, rhizomatous, or decumbent and rooting at the 
base; inflorescence an open or contracted panicle, sometimes with rather simple 
branches and the spikelets unilaterally disposed along them. Disarticulation below the 
spikelets. Spikelets more or less flattened on the first glume side and convex on the 
second glume side, sometimes biconvex or even somewhat laterally compressed; first 
glume usually much reduced, rarely as much as three-fourths as long as the spikelet, 
mostly 1-3-nerved, membranaceous; second glume and lower (sterile) lemma subequal, 
ca. as long as the spikelet, membranaceous, 3-11-nerved; sterile lemma often containing 
an abortive or well-developed palea, and rarely a staminate flower; upper (fertile) floret 
stiff or rigid, awnless, the lemma usually smooth and shining, its margins inrolled over 
the edges of a flat or somewhat convex palea of similar length and texture; lodicules 2, 
truncate; anthers usually 3; ovary with 2 separate style branches, these naked near the 
base; stigmas plumose; caryopsis elliptical or obovate, dorsally flattened, with a large 
embryo. 

Panicum is an enormous genus, primarily distributed in warm cli- 
mates of both eastern and western hemispheres. Early authors used 
the name in a very inclusive sense, involving most of the species of the 
subfamily, but a general tendency has been to remove groups of 
species as segregate genera. Related or segregate genera in our flora 
include Brachiaria, Digitaria, Echinochloa, Homolepis, Hymen- 
achne, Ichnanthus, Isachne, Lasiacis, Leptocoryphium, Oplismenus, 
Paspalum, Pseudechinolaena. The genus Panicum is generally rec- 
ognized by the spikelets, which are borne in panicles and are awnless, 
dorsally compressed, and with a short first glume and subequal second 
glume and sterile lemma that conceal the rigid floret. A recent pro- 



BURGER: FLORA COSTARICENSIS 351 

posal has been made by Gould to remove the subgenus Dichanthelium 
as a genus; however, these plants lose their distinctiveness in the 
tropics, and I have continued to include them in Panicum. (Pani- 
coideae: Paniceae.) 

KEY TO SPECIES OF Panicum 

la. Spikelets more than 3 mm. long 2 

Ib. Spikelets less than 3 mm. long 11 

2a. Fertile lemma rugose P. maximum 

2b. Fertile lemma smooth 3 

3a. Spikelets (at least those in axillary inflorescences) pubescent 4 

3b. Spikelets all glabrous (see also P. cordovense) 5 

4a. Sheaths, blades, and internodes densely papillose-hispid; spikelets acumi- 
nate, all pubescent P. rudgei 

4b. Sheaths, blades, and internodes sparsely pubescent; spikelets blunt, only 

those in axillary inflorescences pubescent P. cordovense 

5a. Leaf sheaths and blades densely papillose-pubescent 6 

5b. Leaf sheaths and blades glabrous or only slightly pubescent on collar and edges 7 

6a. Spikelets 3.5 mm. or less long, usually reddish toward base P. ghiesbreghtii 

6b. Spikelets 4.5-5 mm. long, stramineous or marked with purple . P. parcum 

7a. Spikelets glutinous, often with adhering particles P. glutinosum 

7b. Spikelets not glutinous 8 

8a. Plants with slender rhizomes; panicles 10-15 cm. long; lower floret 
staminate P. aquaticum 

8b. Plants not rhizomatous (submerged nodes sometimes rooting); panicles large, 
35 cm. or more long 9 

9a. Panicle branches simple, conspicuously whorled; spikelets blunt; sterile lemma 

inflated by large palea P. mertensil 

9b. Panicle branches rebranched, not conspicuously whorled; spikelets acute or acumi- 
nate 10 

lOa. Leaf blades elliptical, glabrous, 50 cm. or more long, up to 6 cm. wide; first 

glume more than half as long as spikelet P. grande 

lOb. Leaf blades linear, less than 2 cm. wide; first glume very short; dewlaps deep 
purple P. elephantipes 

lla. Glumes and sterile lemma pubescent 12 

lib. Glumes and sterile lemma glabrous 20 

12a. Leaf blades ovate, less than 4.5 x longer than wide 13 

12b. Leaf blades narrowly ovate to linear, at least 5 x longer than wide 14 

13a. Panicle very diffuse, spikelets diverging on slender pedicels; spikelets 1.3 mm. or 
less long, without glands on sterile lemma P. trichoides 

13b. Panicle slender, of up to 15 short, drooping, 1-sided spikelike racemes; spikelets 
subsessile along their lower sides, at least 1.8 mm. long, usually bearing 2 circular, 

eyelike glands on sterile lemma P. pulchellum 

1 4 a. First glume at least half as long as spikelet 15 

14b. First glume one-third to one-fourth as long as spikelet 17 

15a. Fertile lemma rugose, becoming brown when mature P. sellourii 



352 FIELDIANA: BOTANY 

15b. Fertile lemma smooth, stramineous 16 

16a. Plants bearing exserted terminal panicles only, the spikelets on spreading 
pedicels, sparsely hairy; first glume acuminate, ca. half as long as 

spikelets P. haenkeanum 

16b. Plants bearing exserted primary panicles and small, few-flowered partly in- 
cluded secondary ones, on later leafy branches; spikelets densely pilose; first 

glume obtuse, ca. three-fourths as long as spikelet P. pantrichum 

17a. Leaf blades and sheaths nearly glabrous, except for prominent cilia along the basal 

margins of the blades P. sphaerocarpon 

17b. Leaf blades and sheaths pilose or velvety 18 

18a. Uppermost leaf blades 1-3 cm. long, less than 5 mm. wide; panicles less than 

10 cm. long 19 

18b. Uppermost leaf blades 5-15 cm. long, 10-15 mm. wide P. viscidellum 

19a. Plants branching mostly from the base, forming soft cushions or mounds of foliage; 
leaf blades and sheaths softly and densely pilose, with hairs up to 5 mm. long 

P. laxiflorum 
19b. Plants branching from culm nodes, with axillary tufts of branches; pubescence 

mostly of short hairs 1-2 mm. long P. olivaceum 

20a. Fertile lemma pubescent 21 

20b. Fertile lemma glabrous 23 

21a. Fertile lemma conspicuously woolly at apex and base; spikelets 1.0-1.3 mm. long; 

first glume usually absent; panicle dense P. discrepans 

21b. Fertile lemma with scattered appressed hairs; spikelets at least 1.5 mm. long; first 

glume present 22 

22a. Panicles 2-6 cm. long, the few branches up to 1.5 cm. long, densely flowered to 

their bases P. amndinariae 

22b. Panicles 12-17 cm. long, open, branches up to 10 cm. long, the lower half 

naked, spikelets borne toward tips of branches only P. schiffneri 

23a. Low, mat-forming plants, less than 10 cm. tall P. ciliatum, var. pubescens 

23b. Plants taller, not forming mats or mounds 24 

24a. Inflorescence a short linear cluster of a few spikelets; plants slender, wiry; 

leaf blades involute, 1-2 mm. wide P. stenodes 

24b. Inflorescence a many-flowered panicle; plants various, not wiry, usually with 

flat blades 25 

25a. Spikelets borne in 1-sided racemes along lower sides of primary or secondary 

panicle branches, short-pedicellate and crowded 26 

25b. Spikelets not arranged in 1-sided racemes, randomly disposed in open or crowded 

panicles 33 

26a. Leaf blades ovate, less than 6 x longer than wide 27 

26b. Leaf blades narrowly ovate or linear, more than 10 x longer than wide 29 

27a. Spikelets 1.0-2.5 mm. long 28 

27b. Spikelets 2.5-3.0 mm. long, densely crowded, falcate P. frondescens 

28a. Lower floret producing a naked caryopsis P. irregulare 

28b. Lower floret sterile P. polygonatum 

29a. Leaf blades 2.5-3 cm. wide; plants aquatic P. stagnatile 

29b. Leaf blades mostly 1.5 cm. or less wide; mostly plants of wet ground but not truly 
aquatic 30 



BURGER: FLORA COSTARICENSIS 363 

30a. Leaf blades narrowed to base, not cordate P. laxum 

30b. Leaf blades broad or cordate at base 31 

31a. Panicles rather open, not more than twice longer than wide, the branches up to 11 
cm. long, not bearing long hairs P. boliviense 

31b. Panicles slender, branches not more than 5 cm. long, often bearing long hairs; 

nodes often bearded 32 

32a. Panicles 25-30 cm. long P. pilosum var. lancifolium 

32b. Panicles usually less than 15 cm. long P. pilosum var. pilosum 

33a. Spikelets 2.2 mm. or more long 34 

33b. Spikelets 2.0 mm. or less long 37 

34a. First glume ca. one-fifth as long as spikelet P. parviglume 

34b. First glume half or more as long as spikelet 35 

35a. Leaf blades elliptic, ca. 10 x longer than wide, up to 6 cm. wide; sheaths glabrous; 
plants aquatic P. grande 

35b. Leaf blades linear, more than 15 x longer than wide, rarely more than 15 mm. 

wide; sheaths papillose-hispid; plants of open dry areas 36 

36a. Palea of sterile floret nearly as long as lemma P. cayennense 

36b. Palea of sterile floret one-third as long as lemma P. hirticaulum 

37a. First glume half as long as spikelet or shorter 38 

37b. First glume at least two-thirds as long as spikelet 39 

38a. First glume rudimentary, ca. 0.4 mm. long; ligule a minute membrane 

P. trichanthum 

38b. First glume ca. 1 mm. long; ligule a dense row of bristles up to 3.5 mm. 
long P. hirsutum 

39a. Spikelets 1.7-2.0 mm. long; leaf blades 4-11 mm. wide 40 

39b. Spikelets 1.2-1.6 mm. long; leaf blades 2-3 mm. wide P. parvifolium 

40a. Leaf blades glabrous or with few elongate hairs on cordate base; Spikelets 

1.7-2.0 mm. long P. helobium 

40b. Leaf blades pubescent on both surfaces; spikelets ca. 2 mm. long 

P. errabundum 

Panicum aquaticum Poir., Lam. Encycl. Suppl. 4:281. 1816. Figure 
129. 

Perennial; bases rhizomatous, the rhizomes often vertical; culms erect to decumbent, 
45-130 cm. long; internodes 1.5-4.0 mm. thick, hollow, glabrous; nodes glabrous; leaf 
sheaths ca. as long as the internodes, glabrous; collar and throat sometimes sparsely 
pilose; ligule a short, long-ciliate membrane, in total 0.6-1.7 mm. long; leaf blades 7-27 
cm. long, 5-7 mm. wide, linear, rather abruptly pointed, usually glabrous, rarely 
papillose-pilose near the base above. Peduncles included or exserted up to 5 cm.; panicles 
terminal, broadly ovoid, 10-18 cm. long, 7-11 cm. wide, the longest branch 6-11 cm. long; 
branches ascending, naked near the base, the spikelets usually appressed along the 
scabrous branches. Spikelets ovate, acuminate, (3.0) 3.3-3.7 mm. long, glabrous; first 
glume 1.1-1.5 mm. long, acute, wider than long; second glume 3.3-3.6 mm. long, 9-11- 
nerved; lower (sterile) lemma 3.0-3.5 mm. long, 9-11-nerved, enclosing a well-developed, 
keeled palea and sometimes a staminate flower with 3 orange anthers 1.1-1.3 mm. long; 
palea usually as long as or longer than the lemma; upper (fertile) floret 2.3-3.0 mm. long, 
ovate 2.0-2.5:1, the lemma smooth, shining, rigid, minutely cuspidate; palea similar, flat; 




FIG. 129. Panicum species. P. aquaticum: A, branch of inflorescence; B, base of culm; 
P. arundinariae: C, panicle; D, spikelet; E, fertile floret. 



354 



BURGER: FLORA COSTARICENSIS 355 

anthers 1.6 mm. long; caryopsis ca. 1.7 mm. long, elliptical 2:1. Chromosome number 
n = 36 from a Costa Rican specimen. 

Wet pastures, ditches, sandbars in rivers; scattered in a few 
localities on the Pacific slope; elevations from 50-1,700 m. Known from 
Viente Siete; along the road to Hda. Inocentes; Capellades. Appar- 
ently blooming yearlong. Mexico to Costa Rica, southward to 
Paraguay. West Indies. 

Past descriptions do not mention the presence of rhizomes, but all of 
our specimens have them. One specimen from the marsh along the 
railroad at the Radiografica Transmitter is very tall, up to 2 m. high 
and has hispid foliage. It is otherwise similar to the other specimens 
and has the same chromosome number. 

Panicum arundinariae Trin. ex Fourn., Mex. PI. 2:25. 1881. P. 
mrgultorum Hack., Oesterr. Bot. Z. 51:369. 1901. Figure 129. 

Caespitose perennial; culm bases often decumbent and rooting; culms mostly 50-80 cm. 
long, scrambling in brush or hanging over embankments, branching freely; internodes 
1.0-1.5 mm. thick, hollow, thick-walled, glabrous; nodes bearded; prophylla hirsute, 
10-12 mm. long; sheaths overlapping or shorter than the internodes, minutely ciliate on 
the margin, the surface glabrous except for the bearded auricles and collar; ligule a 
minutely ciliolate membrane, 0.3-0.8 mm. long; leaf blades flat, 4-11 cm. long, 4-9 mm. 
wide, ovate 10-13:1, the base rounded; surfaces nearly glabrous or sparsely appressed- 
pilose, especially toward the tip. Peduncles slender, exserted 4-17 cm.; panicles terminal 
on leafy branches, 2-6 cm. long, small and rather simple, made up of 3-5 short branches 
0.5-1.5 cm. long which are densely flowered to their bases. Spikelets elliptical-obovate, 
1.7-1.9 mm. long, glabrous, dorsally compressed but slightly biconvex, blunt; first glume 
a nerveless translucent scale, 0.5-0.6 mm. long; second glume and lower (sterile) lemma 
very similar, equal, 5-nerved; upper (fertile) floret 1.5-1.6 mm. long, blunt, broadly 
elliptical, less than twice as long as wide; lemma finely striate, stramineous, shining, 
with scattered fine pilose hairs; palea similar, slightly convex; lodicules 2, truncate; 
anthers 3, orange, 0.7 mm. long; styles 2, separate; caryopsis elliptical 1.5:1, 1.1 mm. 
long, yellowish, with a red dot over the embryo. Chromosome number n = 18 from Costa 
Rican specimens. 

Scattered in the Meseta Central, San Ramon area, and the Cartago 
Valley, at elevations of 1,000-1,800 m. In shrubbery, often on brushy 
roadbanks. June to February. Southern Mexico to Panama. 

Panicum boliviense Hack., Fedde Repert. Sp. Nov. 11:19. 1912. 

Duration indefinite, probably perennial; culms 60-125 cm. long, the bases often long- 
decumbent and rooting at the nodes, branching from the rooted nodes and middle nodes 
of erect portions; prophylla ca. 5 cm. long; culm internodes 1.5-2.0 mm. thick, hollow, 
glabrous; nodes glabrous or slightly bearded; leaf sheaths shorter than or equal to the 
internodes; overlapping margin pilose-ciliate; collar pilose; surface glabrous or 
papillose-pilose toward the apex; ligule a minutely ciliolate membrane, 0.2-0.5 mm. long; 
leaf blades glabrous, or pilose just above the ligule, more or less cordate at the base, 
with a very short pseudopetiole; length usually 15-17 (32) cm., width 11-15 mm., the 



356 FIELDIANA: BOTANY 

length 11-14 x the width. Inflorescence terminal on leafy branches; peduncle included in 
the uppermost sheath or exserted up to 10 cm.; panicles open, elliptical, 18-32 cm. long, 
3-5 x as long as wide, the longest branch 6-14 cm. long; spikelets densely clustered and 
short-pedicellate on the lower sides of the triquetrous primary or secondary branches. 
Spikelets 1.3-1.8 mm. long, ovate, rather blunt, biconvex in lateral view, distended by 
the enlarged palea of the sterile lemma and often gaping; first glume 0.7-1.0 mm. long, 
broadly ovate, usually 3-nerved, acute; second glume 1.3-1.7 mm. long, 5-nerved, con- 
vex; lower (sterile) lemma 3-nerved, 1.2-1.6 mm. long, enclosing an enlarged palea 
nearly as long; upper (fertile) floret elliptical or ovate, 1.1-1.6 mm. long, acute, 
stramineous; palea similar, flat; lodicules 2, truncate; anthers usually 2, purple, 0.5-0.6 
mm. long. Chromosome number n = 20 from a number of Costa Rican specimens. 

Wet forested areas, mostly near the Pacific Coast, around the Bay of 
Nicoya; Cariblanco; Osa Peninsula; Buenos Aires; elevations mostly 
sea level to 400 m. June to August. Southern Mexico to Panama, south 
to Argentina; Cuba. 

Panicum boliviense is very similar to P. laxum in spikelet structure 
and size and shares the same chromosome number. It differs from P. 
laxum primarily in size and vigor, in the wider and more cordate- 
based leaf blades, and the larger and more branched inflorescence. The 
two appear to be very closely related, with P. boliviense perhaps 
representing a large extreme of P. laxum. 

Panicum cayennense Lam., Tabl. Encycl. 1:173. 1791. 

Caespitose annual; culms erect or spreading, 18-40 cm. tall, in small clumps, branching 
from the base and middle nodes; internodes 1-2 mm. thick, hollow, papillose-hispid to 
nearly glabrous; leaf sheaths mostly overlapping, papillose-hispid; ligule a short mem- 
brane, ca. 0.3 mm. long, bearing a row of stiff hairs, in total 0.8-1.2 mm. long; leaf blades 
linear, 9-18 cm. long, 5-8 mm. wide, more or less papillose-pilose on the surface. Pedun- 
cles mostly included in the upper sheaths; panicles several, terminal and from the upper 
leaf axils, commonly becoming tangled into an elongated compound inflorescence; indi- 
vidual panicles 5-16 cm. long, 4-8 cm. wide, ovoid; branches divaricate; pulvini pubes- 
cent, branches scabrous; pedicels divaricate, the terminal ones elongated, stiff. Spikelets 
obovate 1.6-1.75:1, short-cuspidate, biconvex, 2.1-2.3 mm. long; first glume 1.3-1.6 mm. 
long, broadly ovate, 5-nerved; a stout rachilla internode ca. 0.4 mm. long between the 
first and second glumes; second glume 1.8-2.0 mm. long, 7-nerved; lower (sterile) lemma 
1.8-2.0 mm. long, 5-nerved, enclosing a well-developed palea ca. 1.5 mm. long, some- 
times with abortive anthers; upper (fertile) lemma 1.4-1.5 mm. long, broadly elliptical 
1.4-1.5:1, rigid, shining, stramineous; palea similar, convex; lodicules 2, truncate; an- 
thers 3, deep purple, 0.7-0.9 mm. long; styles 2, separate; stigmas purple. 

This species has been collected repeatedly on the savannas around 
Buenos Aires; Boruca, Hda. Argentina; elevations 380-450 m. Feb- 
ruary to July. Southern Mexico to northern South America; Cuba. 

Panicum ciliatum Ell., Bot. S.C. & Ga. 1:126. 1816, var. pubescens 
(Vasey) Freckmann, comb. nov. P. laxiftorum Lam., var. pubescens 



BURGER: FLORA COSTARICENSIS 357 

Vasey, Contr. U.S. Natl. Herb. 3:30. 1892. P. strigosum Muhl. in Ell., 
Bot. S.C. & Ga. 1:126. 1816. 

Caespitose perennial, forming dense rosettes or circular mats; plants 6-15 cm. tall; 
culms branching from the base or lowermost node; internodes slender, less than 0.5 mm. 
thick, hollow, thin- walled, glabrous; nodes appressed-pilose; foliage leaves 2-3 per culm; 
leaf sheaths overlapping, mostly glabrous except for the finely pilose overlapping mar- 
gin; ligule a minute ciliolate membrane, 0.1-0.2 mm. long; leaf blades flat, ovate 6-7.5:1, 
rounded to the base, glabrous or sparsely pilose on the surface, strongly pectinate-ciliate 
on the margins nearly to the tip with hairs up to 3 mm. long. Inflorescence terminal; 
peduncle exserted 2-5 cm.; panicles pyramidal, 2-4 cm. long, 1-3 cm. wide, the rachis and 
branches conspicuously soft-pilose, the hairs up to 2 mm. long; pedicels elongate, 
spreading. Spikelets 1.3-1.5 mm. long, obovate 1.7:1, glabrous, obtuse; first glume 
broadly ovate, ca. as wide as long, acute, 1-nerved, 0.6-0.7 mm. long; second glume and 
lower (sterile) lemma subequal, 1.2-1.3 mm. long, 5-nerved; sterile lemma with a hyaline 
palea 0.3-0.5 mm. long; upper (fertile) floret ca. 1.0 mm. long, elliptical, the lemma 
smooth and shining, rigid; palea similar, flat; anthers 3, purple, ca. 0.3 mm. long. 

There are no recent collections of this species from Costa Rica. A 
single old collection by Oton Jimenez is in US. The locality is indicated 
as "de Candelaria a San Cristobal." Since this is primarily a species of 
low coastal savannas, the locality is somewhat suspect. Southern 
Mexico, Belize, Guatemala, Nicaragua; Colombia; West Indies; south- 
eastern United States. 

This taxon belongs to the informal group Laxiflora of Hitchcock and 
Chase, included in the subgenus Dichanthelium. Its closest relative in 
our flora is P. laxiflorum. 

Panicum cordovense Fourn., Mex. PI. 2:26. 1881. Figure 130. 

Duration indefinite, probably perennial; plants creeping or scrambling in brush; bases 
of culms long-decumbent and rooting; total length up to 2 m. , the ascending portions 
40-120 cm. long, branching freely, the branches divaricate; internodes 1-2 mm. thick, 
hollow, glabrous; nodes glabrous or hispid, dark; leaf sheaths shorter than the inter- 
nodes, glabrous, papillose, or papillose-hispid; margins finely ciliate; ligule an erose 
membrane, 0.2-0.4 mm. long; leaf blades 5.5-12 cm. long, 8-12 mm. wide, flat, narrowly 
ovate 7-11:1, slightly oblique at the subcordate base; surfaces glabrous or sparsely 
papillose-hispid; pseudopetioles very short, less than 1 mm. long. Terminal inflores- 
cences large and open, 13-30 cm. long, 13-26 cm. wide, pyramidal, few-flowered; 
branches solitary or paired; pulvini bearded. Spikelets of terminal panicles solitary or 
paired, on unequal pedicels, appressed along the primary or secondary panicle branches, 
glabrous, ovate 2.4-2.6:1, blunt-tipped, strongly nerved, 3.1-3.6 mm. long; first glume 
2.2-2.6 mm. long, ovate 1.8:1, blunt-tipped, 3-nerved; second glume 2.9-3.2 mm. long, 
5-7-nerved, slightly shorter than the spikelet; lower (sterile) lemma 2.8-3.2 mm. long, 
7-nerved, lacking palea and flower; upper (fertile) floret 2.4-3.1 mm. long, obovate 2.2- 
2.3:1, the lemma stramineous, smooth, shining, rigid, apiculate; palea similar, flat; 
lodicules 2, truncate; anthers 3, 1.1-1.7 mm. long, orange; styles 2, separate; stigmas 
purple. The spikelets of the terminal panicles seem to set seed rarely, and the one 
caryopsis seen was small (1.2 mm. long). Axillary panicles small, few-flowered, the 
spikelets crowded, some hidden in the sheaths; spikelets of the axillary panicles finely 




Jf/t 



FIG. 130. Panicum cordovense. A, panicle; B, spikelet from a terminal panicle; C, 
spikelet from an axillary panicle; D, fertile floret. 



358 



BURGER: FLORA COSTARICENSIS 359 

pilose, 3.5-3.8 mm. long, slightly wider than those of the terminal panicles, ovate 1.9- 
2.1:1; fertile floret obovate, 2.8-3.0 mm. long; anthers small, 0.3-0.4 mm. long, remaining 
trapped within the floret; caryopsis broadly elliptical 1.5:1, tan. Chromosome number n 
= 27 from a Costa Rican specimen. 

Moist forested areas, brushy roadsides, trails; mostly on the vol- 
canoes of the Cordillera Central; San Ramon area; moist lower canyons 
of the Talamanca Range; Finca Las Cruces, San Vito. Blooming mostly 
from June to October. Southern Mexico to Brazil and Bolivia. 

This species is peculiar in having both glabrous chasmogamous 
spikelets in the terminal inflorescences and pubescent cleistogamous 
ones in the later axillary inflorescences. Panicum pantrichum is simi- 
lar. Although this dimorphism is somewhat similar to that which oc- 
curs in the subgenus Dichanthelium, the similarity is probably due to 
convergence, since the two groups are entirely different in vegetative 
habit and chromosome number. 

Panicum discrepans Doell in Mart., Fl. Bras. 2:2:252. 1877. Figure 
131. 

Perennial; culms 25-40 cm. long, decumbent, unbranched; internodes 1.0-1.5 mm. 
thick, solid, glabrous; nodes dark, contracted, glabrous; foliage at the base of the culms 
densely and conspicuously pilose; leaf sheaths shorter than the internodes, all except the 
lowermost glabrous except for the ciliate margins; ligule a dense row of stiff white hairs, 
2.0-2.5 mm. long, conspicuous; leaf blades 1.5-3.5 mm. long, 2-3 mm. wide, glabrous, 
more or less inrolled. Peduncle exserted up to 4 cm.; panicles terminal on the culms, in 
our specimen 2-3 cm. long, contracted, the branches ascending, to 1.5 cm. long; spikelets 
dark, densely crowded along the branches, short-pedicellate. Spikelets 1.1-1.2 mm. long, 
ovate 2.5:1, glabrous externally, plano-convex; first glume absent in ours, said by Hitch- 
cock to be up to half as long as the spikelet in some; second glume and lower (sterile) 
lemma equal, as long as the spikelet, nerves 3, nearly parallel, purple; the internerves 
purple-dotted; upper (fertile) floret ca. 1.0 mm. long, ovate 2:1, the lemma strongly 
convex, densely woolly at base and apex; palea equal, flat; lodicules 2, truncate; anthers 
3, purple, 0.3-0.4 mm. long. 

The only known Central American specimen of P. discrepans is the 
following: Prov. Puntarenas: Muy comiin en los bordes de una charca 
estacional. Tallos postrados. Mezclado con Cyperus haspan. Cerca del 
cruce a Buenos Aires de Osa. Bermudez & Sanchez 329, 23 May 1976. 
Brazil, Cuba. 

Panicum elephantipes Nees, Agrost. Bras. 165. 1829. 

Duration indefinite, probably perennial; culms up to 160 cm. long, the basal portions of 
the stems submerged and rooting profusely from the nodes; branching not seen; inter- 
nodes ca. 1 cm. thick, hollow, thin-walled, glabrous; nodes contracted, purple, glabrous; 
leaf sheaths mostly overlapping, glabrous, with hyaline margins; auricles ciliate; dewlap 
conspicuous, deep purple; ligule a dense row of white hairs, 2-3 mm. long; leaf blades 
30-54 cm. long, 11-20 mm. wide, with a broad, subcordate base, glabrous or with a few 




FIG. 131. Panicum discrepans. A, blooming plant; B, two views of a spikelet; C, 
fertile floret, pubescent at base and tip. 



360 



BURGER: FLORA COSTARICENSIS 361 

hairs on the upper surface behind the ligule. Peduncle included in the uppermost sheath; 
panicles terminal, solitary, up to 30 cm. long and half as wide, ovoid, rather dense, the 
numerous branches ascending, scabrous; spikelets mostly paired and unequally pedicel- 
late, appressed along the branches. Spikelets ovate 4:1, acuminate, 3.8-4.2 mm. long, 
glabrous; first glume triangular 2:1, hyaline, faintly nerved, 1.0-1.2 mm. long; second 
glume and lower (sterile) lemma equal, as long as the spikelet, 5-7-nerved; upper (fertile) 
floret ca. 3.5 mm. long, ovate 4:1, acuminate; lemma firm but not indurate, shining, the 
edges thin and scarcely inrolled; palea similar, flat; lodicules 2, bifid; anthers 3, orange, 
1.6-1.8 mm. long; styles 2, separate, naked below, the stigmas purple or brown, ex- 
serted; caryopsis not seen. 

The following is the only collection from Costa Rica: Prov. Limon, 
sandbar, Barro de Colorado, elevation 1 m., 14 December 1974, Pohl & 
Lucas 13026. El Salvador, Honduras, Guatemala, Belize; West Indies; 
tropical South America to Argentina. 

Panic urn errabundum Hitchc., Contr. U.S. Natl. Herb. 22:494. 
1922. 

Duration indefinite, probably perennial; culms long-decumbent and rooting and 
branching at the prostrate nodes, the total length up to 140 cm.; internodes glabrous, 
purple-spotted, 1.0-1.5 mm. thick, hollow; nodes purple, not prominent; sheaths shorter 
than the internodes, spreading-pilose; ligule a minute membrane, ca. 0.2 mm. long; leaf 
blades flat, the base cordate, 4-8 cm. long, 4-8 mm. wide, softly pilose above and below. 
Inflorescences terminal on erect portions of culms; panicles very open, broadly pyrami- 
dal, up to 10 cm. long and 12 cm. wide; peduncle, branches, and pedicels glabrous, 
purplish; branches solitary or paired, strongly divergent; pedicels divergent, 1-3 times 
as long as the spikelets, flexuous. Spikelets ovate 2:1, strongly convex or biconvex, 
purple, glabrous, 1.9-2.1 mm. long; first glume broadly ovate, acute, 3-nerved, ca. 1.5 
mm. long; second glume as long as the spikelet, 5-nerved; lower (sterile) lemma 4- 
nerved, bulging, inflated by the enlarged palea that is ca. as long as the lemma, char- 
taceous, with inflexed margins; upper (fertile) lemma stramineous, shining, faintly 
striate, ca. 1.7 mm. long, elliptical 2:1; anthers 3, purple, ca. 1 mm. long; style branches 
2, separate. 

The following Costa Rican specimen is the only recorded North 
American collection: Prov. Puntarenas, Canas Gordas, elevation 1,160 
m., dense undergrowth in a marsh, old crater, 26 September 1968, P. 
& D. 11159. This species was described by Hitchcock from Parika, 
British Guyana. This species belongs to the group Parvifolia. See 
further discussion under P. helobium. The specific epithet, unex- 
plained by Hitchcock, means "wandering" and refers apparently to the 
decumbent habit of the plants. 

Panicum frondescens Mey., Prim. Fl. Esseq. 56. 1818. Figure 132. 

Duration indefinite, probably perennial; culms long-decumbent and rooting at the 
decumbent nodes; erect branches from the rooted nodes 10-60 cm. long, sparsely 
branched from the lower and middle nodes; internodes 1-2 mm. thick, hollow, glabrous 
or with a woolly line down one side; nodes dark, not prominent, mostly glabrous; leaf 







B 




FIG. 132. Panicum frondescens. A, panicle; B, panicle branch with spikelets; C, 
stoloniferous base of plant; D, spikelet; E, fertile floret. 



362 



BURGER: FLORA COSTARICENSIS 363 

sheaths shorter than the internodes, pilose-ciliate on the overlapping margin; apex cilio- 
late, auriculate; collar with a pilose-ciliolate external ligule; internal ligule a short mem- 
brane, ca. 0.2 mm. long, continuous with the margin of the auricles; leaf blades flat, 
ovate 4-6:1, 2.5-9.5 cm. long, 7-17 mm. wide, rounded at the base to a short 
pseudopetiole ca. 1 mm. long; surfaces glabrous to sparsely appressed papillose-pilose. 
Peduncle puberulent or pilose; rachis puberulent, especially around the nodes; panicles 
terminal on leafy branches, dense, spirelike, the length 4-6 x the diameter, composed of 
numerous ascending or drooping 1-sided racemes, the lowermost ones remote, the up- 
permost densely crowded. Spikelets densely crowded along the lower sides of the 
branches, short-pedicellate in pairs that alternate along the lower 2 sides of the triquet- 
rous rachis. Spikelets 2.5-2.7 (3.1) mm. long, falcate, biconvex, somewhat laterally com- 
pressed; first glume broadly ovate, acute, 1.0-1.1 mm. long, 3-nerved; second glume 2.3 
(2.8) mm. long, 5-nerved, strongly convex; lower (sterile) lemma 2.5 (2.8) mm. long, 
slightly longer than the second glume, 5-nerved, strongly convex, saccate just above the 
base; palea membranaceous, 1.4-1.5 mm. long; upper (fertile) floret 1.3-1.5 mm. long, the 
lemma smooth, shining, rigid, ovate, acute, dorsally compressed; palea similar, flat; 
anthers 3, 0.5-0.6 mm. long; styles 2, separate; caryopsis ca. 0.8 mm. long, elliptical, 
amber. 

This species is found occasionally in rain forests, cacao groves, or 
shallow standing water at elevations below 100 m. Limon, Zent, La 
Bomba, Cahuita, Siquirres, Guapiles, Dos Bocas, Rincon de Osa, 
Puerto Cortes, Palmar. Southern Mexico to Honduras and Costa Rica; 
Caribbean Islands; South America to northern Argentina. 

The spikelets of P. frondescens resemble those of species of Sac- 
ciolepis in being biconvex and possessing a palea in the sterile lemma; 
however, there is no similarity in the general structure of the plants. 
The closest relatives of this species appear to be the members of the 
Panicum laxum alliance, which resemble it in general plant structure 
and the possession of an enlarged palea in the sterile lemma. 

Panicum ghiesbreghtii Fourn., Hex. PL 2:29. 1881. 

Duration indefinite, probably annual; plants caespitose; culms 35-110 cm. long, de- 
cumbent to ascending, branching from the base and middle nodes; internodes 1.0-2.5 
mm. thick, hollow, papillose-pilose; nodes bearded; leaf sheaths mostly shorter than the 
internodes, papillose-pilose; ligule a short membrane, 0.3-0.5 mm. long, bearing a dense 
row of straight white cilia, in total 1-2 mm. long; leaf blades linear 27-40:1, 11-30 cm. 
long, 4-8 mm. wide, flat, papillose-pilose; midrib conspicuous, white. Peduncles sparsely 
papillose-pilose; panicles terminal and axillary, open, ovoid-pyramidal 2-3:1; spikelets on 
divergent pedicels. Spikelets biconvex, 3.2-3.7 mm. long, ovate, acuminate 2.3:1; first 
glume broadly ovate, 1.8-2.3 mm. long, 5-nerved; second glume and lower (sterile) 
lemma separated from the first glume by a thick rachilla internode ca. 0.5 mm. long; 
second glume 2.6-3.1 mm. long, 7-nerved; lower lemma 2.8-3.5 mm. long, 9-nerved; 
upper (fertile) lemma ovate ca. 2:1, 2.2-2.4 mm. long, shining, rigid, stramineous; palea 
similar, flat; anthers 3, purple, ca. 1.0 mm. long. 

Coastal low savannas, from Hacienda la Taboga to the Nicaraguan 
border, at elevations below 200 m.; western portions of the Meseta 



364 FIELDIANA: BOTANY 

Central, where probably introduced. June to February. Southern 
Mexico to Panama and Colombia; West Indies. 

This species is closely related to P. hirticaulum, P. parcum, and P. 
cayennense. Although Hitchcock and Chase assumed that it is a per- 
ennial, it is impossible to be certain of this from herbarium specimens. 

Panicum glutinosum Swartz, Prodr. Veg. Ind. Occ. 24. 1788. 

Caespitose perennial; culms 55-160 cm. long, unbranched, the bases sometimes de- 
cumbent and rooting; plants sprawling in brush; internodes 2-4 mm. thick, hollow, gla- 
brous; nodes glabrous; leaf sheaths longer or shorter than the internodes, glabrous; 
sheath auricles and dewlaps pilose; ligule a minute membranaceous rim, 0.1-0.2 mm. 
long; leaf blades 11-44 cm. long, 8-28 mm. wide, mostly glabrous except for prominent 
papillose-based cilia on the lower margins, rarely sparsely papillose-hispid above. 
Inflorescences solitary, terminal; peduncle exserted up to 17 cm.; panicle open, broadly 
ovoid, 12-35 cm. long, 7-17 cm. wide, the longest branch up to 17 cm. long; lower 
branches verticillate; pulvini pilose; spikelets borne on elongate spreading pedicels, 
mostly toward the outer half of the branches; pedicels 2-many x as long as their 
spikelets. Spikelets 3.0-3.5 mm. long, plump, obovate 2:1, glabrous, the bracts usually 
glutinous and becoming covered with attached particles, rarely trapping insects; first 
glume nearly as long as the spikelet, 2.8-3. 1 mm. long, 5-nerved, ovate, covering most of 
the sterile lemma; second glume 2.5-3.0 mm. long, very broad, the margins enwrapping 
the edges of the sterile lemma; nerves 7; lower (sterile) floret 2.6-3.2 mm. long, 5-nerved; 
sometimes enclosing a narrow, tongue-shaped nerveless palea 2.0-2.4 mm. long; upper 
(fertile) floret 2.8-3.1 mm. long, obovate, acute; lemma smooth, shining, rigid, stramine- 
ous; palea equal; anthers 3, purple, 1.0-1.5 mm. long; flowers apparently mostly cleis- 
togamous, the anthers remaining trapped within the lemma, along with a developing 
caryopsis. Chromosome number n = 20 from Costa Rican and Venezuelan specimens. 

Brushy areas at intermediate altitudes from 700-1,800 m. elevation; 
central and southern Costa Rica; San Ramon area; Tejar, Agua 
Caliente, Bajo Pacuare, San Cristobal Norte, Helechales del General, 
Canas Gordas. Apparently blooming yearlong. Mexico to Bolivia and 
Paraguay; West Indies. 

The unique feature of this species is the viscid character of the outer 
bracts of the spikelets, which causes them to adhere to passing ani- 
mals. The species has no obviously close relatives in our flora. 

Panicum grande Hitchcock & Chase, Contr. U.S. Natl. Herb. 
17:529. 1915. Figure 133. 

Duration perennial; plants coarse, 2-4 m. tall, erect from decumbent or stoloniferous 
bases; culms mostly unbranched; lower nodes often producing masses of roots where 
submerged in water; internodes 1-1.5 cm. thick, hollow, glabrous; nodes appressed-silky; 
sheaths mostly longer than the internodes, glabrous, the margins hyaline; ligule a thick, 
minutely ciliolate membrane, 1.0-2.5 mm. long; dewlap sometimes slightly pubescent, 
dark colored; leaf blades large, flat, usually 35-75 cm. long, 3-5 cm. wide, elliptical 
19-15:1, tapering to the narrow base, the apex not acuminate; surfaces glabrous; margins 
strongly scabrous. Inflorescences terminal on leafy culms; peduncle glabrous, exserted; 




FIG. 133. Panicum grande. A, panicle; B, leaf blade; C, two views of a spikelet. 

365 



366 FIELDIANA: BOTANY 

panicle large, open-pyramidal, 55-70 cm. long, 25-40 cm. wide, the branches whorled, 
spreading or ascending, the secondary and tertiary branches and spikelets more or less 
appressed along the primary branches; pedicels appressed, mostly shorter than the 
spikelets. Spikelets ovate 3.1-3.4:1, glabrous, 2.5-2.9 mm. long, rarely longer in terminal 
spikelets; first glume ovate, acute, 3-nerved, 1.6-2.0 mm. long, ca. two-thirds as long as 
the spikelet; second glume and lower (sterile) lemma subequal, exceeding the fertile 
floret, 2.0-2.5 mm. long, 5-nerved; upper (fertile) floret 1.5-1.8 mm. long; lemma ellipti- 
cal, 2.0-2.4:1, stramineous, shining; palea similar; lodicules 2, truncate; anthers 3, pur- 
ple, 0.7-1.1 mm. long; styles 2, separate; caryopsis 0.9-1.1 mm. long, oblong-elliptical, 
plump, gray, the lower portion suffused with purple. Chromosome number n = 10 from 
Costa Rican specimens. 

Forming large colonies mostly in coastal marshes, usually in stand- 
ing water or on mud; Lago de Arenal, Matapalo, Tarcoles, Golfito, 
Pigres, along the canal between Parismina and Moin; San Isidro, 
Chitaria, Guapiles. September to December. Guatemala to Panama; 
northern South America to Brazil. 

This is one of the largest and most conspicuous of the herbaceous 
grasses. 

Panicum haenkeanum Presl, Rel. Haenk. 1:304. 1830. P. cos- 
taricense Hack., Oesterr. Bot. Z. 51:428. 1901. 

Duration indefinite; plants sprawling or trailing, scrambling into brush, rooting from 
the lower nodes; culms to 2 m. long, branching from the base and middle nodes; inter- 
nodes elongated, ca. 1 mm. thick, hollow, sparsely pilose; nodes not prominent, glabrous; 
leaf sheaths much shorter than the internodes, sparsely pilose; collar densely bearded; 
ligule a short membrane, 0.3-0.5 mm. long; leaf blades flat, ovate ca. 10:1. Peduncles 
short-exserted; panicles terminal on leafy culms, ovoid, rather delicate, 7-16 cm. long; 
spikelets widely spreading on delicate, flexuous, elongated pedicels. Spikelets elliptical 
2.5-3.0:1, acute, 2.4-2.6 mm. long; first glume broadly ovate, acuminate, 3-nerved, the 
lower margins overlapping; second glume and lower (sterile) lemma subequal, 5-nerved, 
2.2-2.5 mm. long, very sparsely pilose with fine hairs; upper (fertile) lemma 1.7 mm. 
long, elliptical 2:1, stramineous, shining; palea similar, flat; anthers 3, tan, 0.9-1.0 mm. 
long. Chromosome number n = 10 from a Costa Rican specimen. 

Rare or overlooked; gallery forests along streams in savannas; Las 
Animas, Liberia; General Valley; Boruca. Elevations 200-300 m. Oc- 
tober to February. Mexico; Costa Rica and Panama. 

Panicum helobium Henrard, Meded. Rijks-Herb. Leiden 40:52. 
1921. The name has usually been credited to Mez ap. Ekman, Ark. 
Bot. II, (4):23, pi. 1, fig. 6. 1912. This is, however, a nomen nudum. 
Henrard, although citing Mez, gives a full Latin description. 

Duration indefinite; culms long-decumbent, creeping and rooting at the nodes, the 
decumbent portions branching freely; erect culms unbranched, 10-70 cm. tall; prophylla 
prominent, broad, up to 5 mm. long; culms glabrous, hollow, ca. 1 mm. thick; nodes dark, 
not prominent; leaf sheaths mostly shorter than the internodes; glabrous; ligule a brown- 



BURGER: FLORA COSTARICENSIS 367 

ish membrane, 0.3-0.7 mm. long; blades flat, cordate-based, 2-6 cm. long, 4-11 mm. wide, 
glabrous or with a few slender elongate hairs on the rounded basal margins. Peduncle 
exserted up to 10 cm.; panicles solitary, terminal, broadly ovoid, 5-10 cm. long, 5-9 cm. 
wide, many-flowered; peduncle, rachis, and pedicels glabrous; pedicels elongate, flexu- 
ous. Spikelets glabrous, turgid, ovoid to obovoid, usually gaping because of the enlarged 
palea of the sterile lemma, 1.7-2.0 mm. long; first glume ovate, ca. three-fourths as long 
as the spikelet, 3- or rarely 4-nerved; second glume and sterile lemma as long as the 
spikelet, both 5-nerved, or the midnerve frequently suppressed in the sterile lemma; 
palea of the sterile lemma well developed, ca. as long as the fertile floret and distending 
the lemma; fertile lemma 1.3-1.7 mm. long, stramineous, faintly striate; palea similar; 
anthers 3, ca. 1 mm. long. 

A Costa Rican specimen of this species in US is Standley & Valeria 
41575. Prov. San Jose, vicinity of Santa Maria de Dota, altitude 1,500- 
1,800 m., swampy woods, ascending, 26 December 1926-3 January 
1927. The Parvifolia group is a complex of interrelated forms, difficult 
to distinguish with existing literature. Several chromosome numbers 
are involved. I have referred Costa Rican material to P. parvifolium, 
P. errabundum, and P. helobium. A tentative treatment of this group 
is to be found in J. R. Swallen, Notes on grasses. Phytologia 14 
(2):65-76. 1966. 

Panic- um hirsutum Swartz, Fl. Ind. Occ. 1:173. 1797. 

Duration indefinite, probably perennial; caespitose in large clumps, 1-2 m. tall; culms 
simple or branching from middle nodes; prophylla prominent, up to 15 cm. long; inter- 
nodes up to 1 cm. thick, hollow, glabrous or papillose-hispid just below the appressed- 
pilose contracted nodes; leaf sheaths mostly overlapping, sparsely papillose-hispid with 
thick, glassy hairs; dewlap and collar hispid-bearded; ligule a short ciliate membrane, up 
to 2 mm. long; leaf blades flat, up to 70 cm. long and 25 mm. wide, mostly glabrous, but 
with a dense patch of long hispid hairs just behind the membranaceous ligule and 
obscuring it; margins strongly scabrous. Inflorescences terminal on the main culm or a 
leafy branch; peduncles stout, exserted up to 22 cm.; panicles large, densely flowered, 
ellipsoidal, 30-50 cm. long, up to 15 cm. wide; branches ascending, naked only near their 
bases; pedicels short, the lateral ones 0.5-1.5 mm. long, appressed along the panicle 
branches; spikelets very numerous, densely covering the branches. Spikelets 1.8-2.1 
mm. long, glabrous, ovate 2.4-2.7:1, tapering to a rather abrupt point; first glume 
broadly ovate, acute, 3-nerved, 0.9-1.2 mm. long; second glume and lower (sterile) 
lemma about equal, as long as the spikelet, exceeding the fertile floret; second glume 
7-nerved; sterile lemma 7-9-nerved, enclosing a well-developed palea 1.2-1.5 mm. long; 
fertile floret 1.3-1.4 mm. long, elliptical 2:1; lemma rigid, shining, the nerves usually 
visible; palea ca. as long as the lemma, of similar texture; lodicules 2, truncate; anthers 3, 
purple, ca. 0.7 mm. long; styles 2, separate; stigmas purple; caryopsis whitish, elliptical, 
ca. 1 mm. long. 

Apparently rare, along watercourses on the Caribbean Coastal 
Plain. Zent Farm, Rio Bananito, confluence of Rio Puerto Viejo and 
Rio Sarapiqui. February to September. Southern Mexico to Brazil, 
Ecuador, and Trinidad and the West Indies. 



368 FIELDIANA: BOTANY 

Panicum hirticaulum Presl, Rel. Haenk. 1:308. 1830. P. pam- 
pinosum Hitchc. & Chase, Contr. U.S. Natl. Herb. 15:55. 1910; Fair- 
brothers, Amer. J. Bot. 40:710. 1953. 

Caespitose annual in small clumps; culms 25-80 cm. long, erect or the lower nodes 
decumbent and rooting, branching freely from lower and middle nodes; prophylla 3-5 cm. 
long; internodes 1.0-2.5 mm. thick, hollow, papillose-hispid to glabrous; nodes 
appressed-pilose, not prominent; leaf sheaths mostly longer than the internodes, densely 
to sparsely papillose-hispid; ligule a minute membrane, densely ciliate with long hairs, 
the total length 1.5-2.5 mm.; leaf blades flat, 7-27 cm. long, 6-15 mm. wide, papillose- 
pilose to nearly glabrous. Peduncles papillose-pilose; panicles terminal on the main culms 
or on leafy branches, open, ovoid, 13-35 cm. long, 2-4 x longer than wide; longest 
branches up to 13 cm., straight, unbranched and naked below, the spikelets on second- 
ary or tertiary branches appressed to the primary ones on their outer two-thirds. 
Spikelets glabrous, reddish, 2.4-2.5 mm. long, ovate 3:1, acute; first glume 1.2-1.5 mm. 
long, 3-5-nerved, ovate 3:1, acute; second glume 2.1-2.2 mm. long, 7-nerved; lower 
(sterile) lemma 2.2-2.4 mm. long, 9-nerved, enclosing a small membranaceous nerveless 
palea 0.3-0.8 mm. long; upper (fertile) lemma 1.5-1.8 mm. long, elliptical 2:1, smooth and 
shining, stramineous; palea similar, flat; anthers 3, orange or reddish brown, 0.9-1.0 
mm. long; caryopsis broadly elliptical, white, 1.3-1.4 mm. long. 

Bluffs at Playas del Coco; San Luis de Turrubares; Atenas. July to 
October. Southwestern United States to Panama; western South 
America to Argentina. Size ranges for spikelets are based on Central 
American material. Plants from more northerly regions appear to have 
larger spikelets. 

Panicum irregulare Swallen, J. Wash. Acad. Sci. 30:216. 1940. 
Figure 134. 

Duration indefinite; culms extensively creeping and rooting at the lower nodes; flow- 
ering branches arising from the rooted nodes, up to 50 cm. long, not observed to branch; 
attitude not known; culms 1.0-1.5 mm. thick, hollow, glabrous; sheaths mostly shorter 
than the internodes, glabrous, auriculate, with a few hairs on the auricles; ligules not 
seen; leaf blades borne on short, thickened, pubescent pseudopetioles ca. 1 mm. long; 
blades flat, lanceolate, the base somewhat asymmetric, 4.5-7.0 cm. long, 9-15 mm. wide. 
Inflorescences terminal on the erect branches; peduncle slender, exserted 5-15 cm.; 
panicle very open, cylindrical, 16-24 cm. long, composed of about 15 slender drooping 
racemes borne singly or in pairs, remote along the slender rachis; individual racemes 1-2 
cm. long. Spikelets paired, unequally pedicellate along the lower sides of the rachis, 
biconvex, 1.7-2.2 mm. long; disarticulation below the glumes, but the upper floret also 
freely disarticulating; length 1.7-2.2 mm.; first glume ca. 1 mm. long, ovate, acute, 
3-nerved; second glume ca. 2 mm. long, boat-shaped, 5-nerved, acute; lower lemma 
membranaceous, 2.2 mm. long, ovate, acute, boat-shaped, 5-nerved, its palea ca. 1.4 
mm. long, flat or concave, membranaceous, scabrid on the keels; lower flower perfect; 
anthers 3, tan, 1.1-1.2 mm. long; caryopsis developing, free from the lemma and palea, 
0.8 mm. long; upper lemma smooth and shining, dorsally compressed, ovate, acute, ca. 
1.4 mm. long, coriaceous, its thickened margins embracing a palea of similar texture. 

This peculiar species is known only from the type and one other 
specimen, probably from the same locality. Type: Stony river bank, 




FIG. 134. Panicum irregulare. A, growth habit; B, inflorescence; C, spikelet, lateral 
view; D, spikelet, dorsal view; E, lower floret; F, upper floret. 



369 



370 FIELDIANA: BOTANY 

vicinity of El General, Prov. San Jose; altitude 760 m. Skutch 
February 1939. 

In the following respects, this species resembles Pseudechinolaena 
polystachya, which grows in the same area: creeping habit, nature of 
inflorescence, paired spikelets which are biconvex, presence of a palea 
and stamens in the lower floret, oblique-based lanceolate blades. It 
differs in the much smaller spikelets which lack the stipitate bristles of 
Pseudechinolaena. In view of its rarity, it may represent a hybrid 
between this genus and a species of Panicum. 

Panicum laxiflorum Lam., Encycl. Method. Bot. 4:748. 1798. P. 
xalapense H.B.K., Nov. Gen. & Sp. 1:103. 1816. 

Caespitose perennial; plants 10-25 cm. tall, forming dense but soft clumps of many 
culms; branching freely from the lower and middle nodes; internodes ca. 1 mm. thick, 
hollow, pilose; nodes retrorsely pilose; leaf sheaths mostly overlapping, densely pilose 
with spreading or retrorse fine hairs up to 4 mm. long; ligule a sparse to dense row of fine 
white hairs, 0.2-0.3 mm. long; leaf blades soft, flat, rounded to the base, 3-8 cm. long, 3-7 
mm. wide, densely pilose on both surfaces and papillose-ciliate on the margins; blades 
mostly of the same length and rather densely aggregated, the clumps very leafy, only 
the primary panicles protruding above the general level. Peduncle of the primary panicle 
4-5 cm. long; primary panicles 3-7 cm. long, up to 5 cm. wide, pyramidal, few-flowered, 
the branches solitary or paired; spikelets borne on diverging pedicels 1-several times as 
long as the spikelet; rachis and branches softly pilose. Axillary secondary panicles small, 
few-flowered, partially hidden in the leaf sheaths. Spikelets 2.0-2.2 mm. long, finely 
pubescent, obovate 1.7-1.8:1; first glume 0.7-1.0 mm. long, 1-2-nerved, ovate 4:3, acute; 
second glume 1.8-2.1 mm. long, 5-7-nerved; lower (sterile) lemma 1.9-2.0 mm. long, 
7-nerved, containing a hyaline palea 0.7-1.2 mm. long; upper (fertile) floret 1.7-1.9 mm. 
long, elliptic 1.5-1.7:1, stramineous, smooth and shining; palea similar, slightly convex; 
lodicules 2, truncate; anthers 3, purple, 0.4 mm. long; caryopsis obovate 1.2:1, 1.1 mm. 
long. Chromosome number n = 9 from a Costa Rican specimen. 

Occasional, open areas in forests, natural meadows, and road em- 
bankments; Canton de Dota and lower slopes of the Talamanca Range, 
1,400-2,600 m. elevation. Probably blooming yearlong, the primary 
panicles probably produced at the beginning of the rainy season. 

This species belongs to the informal group Laxiflora of the subgenus 
Dichanthelium. In the temperate zone, members of this subgenus 
produce winter rosettes of short, broad leaves. These are apparently 
not produced in our species. A number of species have been described 
which are here included in P. laxiflorum. 

Panicum laxum Swartz, Prodr. Veg. Ind. Occ. 23. 1788. Figure 
136. 

Duration indefinite, probably perennial; culms 15-90 cm. long, rarely up to 120 cm., 
the bases often decumbent and rooting at the nodes, branching from the rooted portion 
or the middle nodes of erect culms; internodes 1.0-1.5 mm. thick, hollow, glabrous; nodes 



BURGER: FLORA COSTARICENSIS 371 

glabrous or rarely retrorsely pilose; prophylla ca. 2 cm. long, ciliate on the keels; leaf 
sheaths shorter than the internodes, the overlapping margin ciliate; surface glabrous or 
papillose-pilose toward the apex; ligule a thin ciliolate membrane, 0.3-0.6 mm. long; leaf 
blades flat, 6-15 (23) cm. long, 4-12 mm. wide, rather thin, rapidly folding or rolling when 
the plants are uprooted; dewlap sometimes pilose; upper surface sometimes pilose above 
the ligule. Inflorescences terminal on leafy culms; panicles usually 5-15 (33) cm. long, 
open, cylindrical or ellipsoidal, with numerous straight primary branches, densely 
covered to their bases with spikelets; spikelets short-pedicellate, borne on the lower 
sides of the triquetrous rachis, in pairs or small groups; larger panicles sometimes with 
evident secpndary branches. Spikelets 1.4-1.8 mm. long, ovoid ca. 2:1, rather blunt, 
biconvex in lateral view, distended by the enlarged palea of the sterile lemma and often 
gaping almost to the base; first glume broadly ovate, acute, 3-nerved, 0.7-1.0 mm. long; 
second glume 1.3-1.8 mm. long, 5-nerved; lower (sterile) lemma similar but 3-nerved, 
1.2-1.7 mm. long, with a membranaceous palea 1.3-1.6 mm. long; upper (fertile) floret 
ovate, 1.2-1.4 mm. long, stramineous; lodicules 2, truncate; anthers 3, yellow or 
splotched with purple, 0.8 mm. long; styles 2, separate; caryopsis 0.8 mm. long, ellipti- 
cal, tan. Chromosome number n = 20 from numerous Costa Rican specimens. 

Common in wet open or partially shaded sites; widespread from sea 
level to 1,200 m. elevation, rarely higher. Blooming April to October, 
occasionally during the rest of the year. Southern Mexico to Paraguay; 
West Indies. 

Panicum laxum is a member of the intricate Laxa group. The 
species of this assemblage are poorly defined and much in need of 
careful biosystematic study. Panicum boliviense may be only a large 
form of P. laxum. Panicum polygonatum is also closely related, but 
has more pointed spikelets lacking a palea in the sterile lemma. 

Panicum maximum Jacq. , Coll. Bot. 1:76. 1786. Figure 135. 

Caespitose perennial in large clumps; plants 1-2.5 m. tall; culms erect, arising from 
hard scaly bases, simple or sparsely branched from the middle nodes; internodes 3-8 mm. 
thick, cylindrical, hollow, glabrous or papillose-pilose below the nodes; nodes contracted, 
appressed-pilose or hispid; sheaths loose, glabrous or more or less papillose or 
papillose-hispid, especially on the margin and toward the apex; collar and dewlap 
bearded; ligule a short, thick, ciliolate membrane, 1-2 mm. long, with a dense tuft of long 
white hairs just above it on the upper surface of the leaf blades; blades flat, up to 65 cm. 
long and 25 mm. wide, mostly glabrous except just behind the ligule; margins with white 
sclerenchyma bands, coarsely scabrous. Inflorescences terminal on leafy culms; panicle 
ovoid, 15-65 cm. long; lower branches verticillate, pilose at the base, scabrous, naked 
near the bases, the longest up to 40 cm. long, ascending; spikelets short-pedicellate in 
small clusters on secondary branchlets, more or less appressed along the primary 
branches. Spikelets 3.3-3.6 mm. long, elliptic-obovate ca. 3:1, biconvex, glabrous; first 
glume rounded, 3-nerved, 1.0-1.2 mm. long; second glume 3.0-3.1 mm. long, 5-nerved; 
lower (sterile) lemma similar, ca. 3.2 mm. long, 5-nerved, with a thin, membranaceous 
palea as long or slightly longer; anthers 3, 1.5-1.8 mm. long; upper (fertile) lemma 
obovate 2.5:1, acute, rigid, stramineous, rugose; palea similar, rugose; lodicules 2, trun- 
cate; anthers 3, orange, 1.2-1.8 mm. long; styles 2, naked for the lower half; stigmas 
purple. Chromosome number n = 18 from a Costa Rican specimen. 




FIG. 135. Panicum maximum. Panicle, plant base, two views of a spikelet, fertile 
floret. 



372 




FIG. 136. Panicum species. P. laxum: A, blooming culm; B, spikelet, lateral view; C, 
lower (sterile) floret, showing palea; P. polygonatum: D, three views of a spikelet. 



373 



374 FIELDIANA: BOTANY 

Cultivated widely as a forage grass at low elevations, especially near 
the coasts, and escaping freely to roadsides; mostly below 500 m., but 
occasionally to 1,100 m. in the Meseta Central. May to November. 
Native to Africa, but now widely cultivated in tropical and warm 
temperate countries. The first herbarium collection from Costa Rica 
dates to 1890. The species is highly apomictic. Local names: Guinea; 
Pasto Guinea. 

Panicum mertensii Roth in Roem. & Schult., Syst. Veg. 2:458. 
1817. Panicum megiston Schult., Mant. 2:248. 1824. Figure 137. 

Robust erect perennial from a knotty crown; culms up to 3 m. long, unbranched; 
internodes 4-8 mm. thick, hollow but containing loose masses or diaphragms of aeren- 
chyma, glabrous; leaf sheaths mostly shorter than the internodes, papillose or 
papillose-hispid, apex auriculate; ligule a thick, erose-ciliolate membrane, 2-3 mm. long; 
leaf blades 30-60 cm. long, 14-25 mm. wide, widest at the middle, glabrous, dark green, 
the midrib white. Peduncles included or exserted up to 5 cm.; panicles terminal on the 
culms, open, ovoid, 40-50 cm. long, 17-30 cm. wide; longest branch up to 16 cm. long; 
branches borne in remote verticels, numerous, straight and stiff, bearing appressed 
solitary or paired spikelets along the outer half; frequently one member of the spikelet 
pair reduced or abortive. Spikelets 3.5-4.0 mm. long, obovate, strongly biconvex, gla- 
brous; first glume 1.4-1.7 mm. long, broadly cordate, wider than long, 3-4-nerved; sec- 
ond glume 3.2-3.8 mm. long, 9-nerved; lower (sterile) lemma 3.2-3.7 mm. long, 9-nerved, 
containing a broad, firm, strongly keeled palea ca. 2.8 mm. long, sometimes with 3 
abortive anthers ca. 0.2 mm. long; upper (fertile) floret 2.7-3.0 mm. long, ovate 2:1, 
acute; lemma smooth, shining, rigid, stramineous; palea similar, convex; anthers 3, 
purple, 1.4 mm. long; caryopsis ca. 1.6 mm. long, elliptical. Chromosome numbern = 20 
from a Costa Rican specimen. 

Rare; shallow water; shady areas at elevations below 100 m.; 
Hacienda La Taboga, Finca La Taboga, Los Chiles. August to 
January. Mexico and Guatemala to northern Costa Rica; Panama 
Canal Zone; Cuba; Trinidad to Paraguay. 

This species is tall and conspicuous. Most specimens are only flow- 
ering tops and do not include basal portions. Amer. Gr. Natl. Herb. 76 
has a large, hard, crownlike base, the culms bearing prop roots from 
their lower nodes. 

Panicum olivaceum Hitchc. & Chase, Contr. U.S. Natl. Herb. 
15:225. 1910. 

Caespitose perennial in small clumps; winter rosettes not seen; plants 15-42 cm. tall, 
the culms erect to sprawling, branching freely from most nodes, producing axillary tufts 
of foliage and small axillary panicles; internodes 1-2 mm. thick, hollow, densely velvety; 
nodes densely bearded; sheaths shorter or longer than the internodes, densely soft- 
pubescent; ligule a dense row of white hairs, 2.0-3.5 mm. long, rarely 0.5 mm. long on 
smaller leaves; leaf blades 2-7 cm. long, 3-9 mm. wide, velvety pubescent on both 
surfaces, ovate 6-8:1, cordate-based. Peduncle of primary panicle exserted 3-11 cm.; 
primary panicle pyramidal, 3-7 cm. long, 2-6 cm. wide, many-flowered; spikelets more or 




FIG. 137. Panicum mertensii. A, panicle; B, spikelet; C, fertile floret. 



375 



376 FIELDIANA: BOTANY 

less appressed along the primary or secondary branches; rachis and peduncle softly 
pilose; pedicels 1-several times as long as the spikelets. Secondary panicles borne at the 
tips of the axillary branches, much smaller than the primary panicle, usually few- 
flowered and with the peduncle included in the uppermost leaf sheath. Spikelets finely 
pubescent, obovate 2.1-1.3:1, biconvex, usually purple, 1.6-2.0 mm. long; first glume 
0.7-0.8 mm. long, broadly deltoid 1:1, the nerves obscure; second glume 1.7-1.9 mm. 
long, 9-nerved, usually slightly shorter than the fertile lemma; lower (sterile) lemma 
1.7-1.8 mm. long, 7-nerved, enclosing a hyaline palea 0.6-0.8 mm. long; upper (fertile) 
floret elliptical ca. 1.5:1, 1.4-1.6 mm. long, rigid, shining, stramineous; palea similar, 
slightly convex; anthers 3, purple, 0.7-1.0 mm. long; styles 2, separate; stigmas purple; 
caryopsis elliptical 1.4:1, white, bearing a red mark near the base on the side opposite 
the embryo. 

Open roadsides and grasslands at intermediate elevations, between 
1,000 and 2,200 m.; occasional. Rincon de la Vieja, San Ramon area, 
Volcan Poas, Volcan Barba, mountains south of the Meseta Central, 
lower portions of the Cordillera de Talamanca. Apparently blooming 
yearlong, but the primary panicles produced mostly from June to Au- 
gust. 

This species belongs to the subgenus Dichanthelium, informal group 
Lanuginosa of Hitchcock & Chase. In our flora, it is most closely 
similar to P. viscidellum, from which it differs in its much smaller size 
and in chromosome number. Southern Mexico to Venezuela. 

Panicum pantrichum Hack., Verh. Zool. Bot. Ges. Wien 1915:72 
(March). P. chiriquiense Hitchc. & Chase, Contr. U.S. Natl. Herb. 
17:527. 1915 (July). Figure 138. 

Duration indefinite, probably perennial; plants extensively creeping and forming flat 
mats, branching freely from the rooted portions; ascending portions of culms 6-25 cm. 
long, unbranched; prophylla 6-12 mm. long; internodes ca. 1 mm. thick, hollow, softly 
pilose; leaf sheaths shorter than the internodes, papillose-pilose or papillose-hispid; 
ligule an erose membrane, 0.2-0.3 mm. long; leaf blades 3.5-8 cm. long, 7-10 mm. wide, 
asymmetrically ovate 5-8:1, flat, velvety-pilose. Peduncles mostly included or short- 
exserted; panicles terminal on ascending leafy branches, 2-10 cm. long, 1-8 cm. wide, the 
larger ones open, pyramidal, the few spikelets appressed along the primary or secondary 
branches; small panicles partly included in the uppermost sheath, consisting of small 
clusters of spikelets. Spikelets of both large and small panicles similar, ovate 2:1, 
pointed, 2.2-2.8 (3) mm. long, the glumes and sterile lemma finely pilose; first glume 
1.6-2.3 mm. long, ovate 1.7-1.8:1, 3-nerved; second glume 2.2-2.7 mm. long, 5-7-nerved; 
lower (sterile) lemma 2.0-2.5 mm. long, 5-6-nerved, the midnerve often suppressed; 
upper (fertile) floret 1.9-2.2 mm. long, elliptic-obovate 1.7:1, the lemma rigid, shining, 
stramineous, the back flattened; tip rounded, not apiculate; palea similar, flat; anthers 3, 
whitish, 0.3 mm. long, remaining trapped within the floret, which is apparently clei- 
stogamous; styles 2, separate; caryopsis broadly elliptical, 0.9-1.4 mm. long, tan to 
reddish, with a reddish linear mark opposite the embryo. Chromosome numbers n = 30 
from a Costa Rican specimen and n = 26 from a Honduran collection. 

Rare; creeping in shade of forests or brush; 1,100-1,700 m. elevation. 




FIG. 138. Panicum species. P. pantrichum: A, blooming plant; B, spikelet; P. 
pulchellum: C, blooming culm; D, spikelet, showing glands on sterile lemma. 



377 



378 FIELDIANA: BOTANY 

San Ignacio, Frailes, Canas Gordas, 10 km. N of San Ramon. June to 
October. Honduras and central Costa Rica and Panama to Brazil and 
Bolivia. 

This species is related to P. cordovense, but differs in size of plant 
parts and spikelets, as well as in the velvety foliage. The spikelets 
appear to be all of one type, whereas those of P. cordovense are gla- 
brous in terminal panicles and pubescent in axillary ones. Spikelets of 
P. pantrichum examined appear to be entirely cleistogamous, the 
small anthers remaining attached to the stigmas on developed 
caryopses. 

Panicum parcum Hitchc. & Chase, Contr. U.S. Natl. Herb. 15:70. 
1910. 

Duration annual; plants caespitose; culms 50-125 cm. long, erect, usually unbranched; 
internodes 2-3 mm. thick, hollow, sparsely papillose-pilose; nodes dark, contracted, 
mostly glabrous; leaf sheaths shorter than the internodes, papillose-hispid; ligule a short 
membrane 0.2-0.5 mm. long, crowned with a dense row of cilia, in total 1.2-1.3 mm. long; 
leaf blades 11-35 cm. long, 6-10 mm. wide, more or less papillose-pilose to nearly gla- 
brous, the tip rather abrupt. Peduncles included or exserted up to 9 cm.; panicles 
terminal, ovoid ca. 2:1, 20-35 cm. long, ca. 12 cm. wide, rather open and few-flowered; 
branches solitary, 9-18 cm. long; pulvini glabrous. Spikelets solitary on the tips of elon- 
gated, stiff pedicels, often purple-marked, 4.7-5.1 mm. long, ovate ca. 3:1, acuminate; 
first glume 3.1-3.7 mm. long, 5-7-nerved, ovate, acuminate; second glume 3.9-4.7 mm. 
long, 9-nerved, ovate, acuminate, longer than the lower (sterile) lemma; lower lemma 
3.8-4.2 mm. long, 9-nerved, with a narrow, hyaline palea 1.5-1.7 mm. long; upper (fer- 
tile) floret 2.8-3.2 mm. long; lemma ovate 2:1, rigid, strongly convex, smooth and shin- 
ing, stramineous, with a large basal scar; palea similar, flat; anthers 3, 1.2-1.4 mm. long, 
deep purple; styles 2, separate; caryopsis elliptical, white. The spikelets have a promi- 
nent, thick rachilla internode, 0.5-0.8 mm. long, between the first and second glumes. 

Rare in Costa Rica; known only from the following two specimens: 
Prov. Guanacaste, Playas del Coco, bluffs, 14 November 1968, P. & D. 
11437; 10 km. by road W of Liberia, savannas, 19 December 1974, Pohl 
& Lucas 13068. Western Central Mexico to Honduras, Nicaragua and 
northwestern Guanacaste. August to December. 

The spikelets in the specimens I have seen are somewhat smaller 
than the range usually assigned to them, but the plants are otherwise 
typical. Panicum parcum was assigned to the informal group Capil- 
laria by Hitchcock and Chase. This group was differentiated from the 
group Diffusa on the basis of annual vs. perennial duration. Spikelets 
and general habit in the two groups are so similar that it is dubious 
whether they can be maintained. Related species in the Costa Rican 
flora include P. ghiesbreghtii and P. hirticaulum. 

Panicum parvifolium Lam., Tabl. Encycl. 1:173. 1791. Figure 139. 




FIG. 139. Panicum species. P. parvifolium: A, blooming plant; B, two views of a 
spikelet; P. stenodes: C, blooming culm; D, group of spikelets. 



379 



380 FIELDIANA: BOTANY 

Duration indefinite, probably perennial; culms up to 60 cm. long, the lower parts 
decumbent and rooting; branching freely from the decumbent portions; internodes less 
than 1 mm. thick, hollow, glabrous; nodes purple, slightly bearded; sheaths shorter than 
the internodes, glabrous or more or less appressed-pilose; ligule a thin membrane, ca. 
0.2 mm. long; leaf blades flat, often ascending, glabrous or appressed-pilose. Inflores- 
cences terminal on leafy ascending portions of the culms, exserted; panicles broadly 
pyramidal, very open; 4-7 cm. long, 4-9 cm. wide; branches solitary, spreading; pedicels 
divaricate, flexuous, 1-3 x as long as the spikelets. Spikelets ovoid-elliptical, plump, less 
than twice as long as wide, often biconvex, glabrous, 1.4-1.6 mm. long; first glume 
broadly ovate, often blunt, 3-nerved, 0.9-1.0 mm. long; second glume as long as the 
spikelet, 5-nerved; lower (sterile) lemma as long as the spikelet, 5-nerved, distended by 
a well-developed palea of nearly equal length; 3 anthers sometimes present; upper (fer- 
tile) floret 1.1-1.5 mm. long, broadly elliptical 7:4, rigid, shining, finely striate, the palea 
of nearly equal length; anthers 3, purple, 0.9-1.1 mm. long; styles 2, separate; stigmas 
dark. Chromosome number n = 18 from a Costa Rican specimen. 

Margins of ponds and streams, often forming large colonies; common 
around the lagunas near Buenos Aires and near San Isidro de el Gen- 
eral and Rivas; Guayabo (Guanacaste). August to January. British 
Honduras to northern South America, southward to Argentina; West 
Indies; also reported from tropical Africa. 

Panicum parvifolium is a common member of the group Parvifolia, 
composed of slender, hydrophytic species having small spikelets. The 
plants show much variation, and the group is in need of biosystematic 
study. See further discussion under P. helobium. 

Panicum parviglume Hack., Oesterr. Bot. Z. 51:429. 1901. 

Perennial, from a hard crown; culms 1 m. or more tall; lower nodes decumbent and 
rooting; branching from the base; internodes 1.5 mm. thick, solid, sparsely papillose- 
hispid; nodes contracted, appressed-pilose; leaf sheaths longer or shorter than the inter- 
nodes, sparsely papillose-hispid; collar hispid-bearded; overlapping margin densely 
ciliate; ligule a densely ciliolate membrane, 0.7-1.0 mm. long; leaf blades flat, 8-20 cm. 
long, 15-25 mm. wide, ovate 5-8:1, rather abruptly rounded to the asymmetric base; 
midrib white, prominent beneath; margins strongly scabrous, with conspicuous white 
marginal sclerenchyma bands; surfaces sparsely papillose-hispid, especially toward the 
tip. Inflorescences terminal on leafy culms; panicle ca. 20 cm. long, 10 cm. wide, nar- 
rowly pyramidal; rachis, branches, and pedicels scabrous; spikelets more or less ap- 
pressed along primary and secondary branches, their pedicels 1-2 x as long as the 
spikelets, and with a few fine hairs at the apex. Spikelets elliptical ca. 2:1, 2.2-2.5 mm. 
long, strongly dorsally flattened, barely acute at the apex, glabrous; first glume a small 
triangular or cufflike nerveless scale, 0.3-0.5 mm. long; second glume and lower (sterile) 
lemma subequal, as long as the spikelet, 5-nerved; upper (fertile) floret somewhat 
shorter, ca. 2 mm. long, broadly ovate 1.5:1, blunt, flattened, stramineous, longitudi- 
nally striate; palea similar to the lemma and slightly convex; lodicules 2, truncate; 
anthers 3, yellow, 1.0 mm. long; styles 2, separate. Chromosome number n = 18 from a 
Costa Rican specimen. 

Rare, at scattered localities in the Meseta Central; Guadalupe, 
Alajuelita, San Miguel; elevation ca. 1,200 m. October to February. 



BURGER: FLORA COSTARICENSIS 381 

This species grows in brush. It was not collected in Costa Rica after 
1912 until our recent collection. Southern Mexico, Guatemala, El Sal- 
vador, Costa Rica. 

Panicum pilosum Swartz, Prodr. Veg. Ind. Occ. 22. 1788, var. 
pilosum. Figure 140. 

Duration indefinite, probably perennial; plants 15-50 cm. tall, the bases sprawling or 
stoloniferous, rooting at the decumbent nodes; erect branches arising from rooted nodes; 
prophylla conspicuous, up to 2 cm. long; culm internodes 1-2 mm. thick, hollow, glabrous 
or papillose-pilose below the nodes; nodes usually densely bearded with spreading fine 
hairs; leaf sheaths mostly longer than the internodes, often divaricate from the internode 
and inrolled, appearing somewhat like elongated pseudopetioles, surface nearly glabrous 
to densely papillose-pilose; ligule absent or represented by a minute ciliolate ridge; collar 
densely pilose; leaf blades 5-20 cm. long, 7-20 mm. wide, narrowly ovate, the length 
mostly less than 10 x the width, acuminate, cordate at the base and with a short, broad 
pseudopetiole; surfaces glabrous to softly pilose. Peduncle exserted 2-15 cm.; inflores- 
cence terminal on erect portions of culms, 6-18 cm. long, narrowly cylindrical, open, 
composed of 7-27 (50) drooping spikelike racemes, these mostly 1.5-2 (6) cm. long. 
Spikelets solitary, paired, or in trios, the groups alternating on both sides of the midrib 
of the lower side of the primary panicle branches; pedicels very short; margins of the 
rachis bearing prominent, papillose-based cilia, 1-3 mm. long. Spikelets 1.4-1.6 mm. 
long, ovate 2.0-2.5:1, acute, biconvex; first glume 0.6-0.8 mm. long, broadly ovate, acute, 
1-3-nerved; second glume and lower (sterile) lemma about equal, as long as the spikelet; 
second glume 5-nerved; sterile lemma 3-nerved, enclosing a well-developed palea 1.0-1.2 
mm. long; upper (fertile) lemma elliptical, 1.2-1.3 mm. long, shining, stramineous, 
strongly convex; palea similar, flat; anthers 3, purplish, 0.5-0.6 mm. long; styles 2, 
separate; stigmas dark; caryopsis elliptical, 1.6:1, 0.8 mm. long, amber. Chromosome 
number n = 10 from Costa Rican and Venezuelan specimens. 

Panicum pilosum is a common weedy species in wet sites, mostly at 
low elevations; sea level to 800 m., rarely up to 1,200 m. Rain forest 
margins and clearings, wet pastures and roadsides, coconut groves and 
beach margins, mostly near the coasts. May to December, possibly 
yearlong. Southern Mexico to Argentina; Caribbean Islands. 

Var. pilosum is very similar to var. lancifolium, which has the same 
chromosome number and probably represents a large extreme of the 
species. 

Panicum pilosum, var. lancifolium (Griseb. ex Hitchc.) Pohl, 
comb. nov. P. distichum Lam., y lancifolium Griseb., Fl. Brit. W. 
Ind. 548. 1864. P. distichum, var. lancifolium Griseb. ex Hitchc., 
Man. Gr. W. Indies 267. 1936. P. milleflorum Hitchc. & Chase, Contr. 
U.S. Natl. Herb. 17:494. 1915. 

Var. lancifolium is similar to var. pilosum in aspect, inflorescence structure, spikelet 
size, 3-nerved lower lemma, enlarged palea, and chromosome number. It differs mostly 
in characters related to plant size and vigor, but there is considerable overlap in most of 
the measurements. Culms 90-150 cm. long, including the long-decumbent basal portions; 




FIG. 140. Panicum pilosum var. pilosum. A, panicle; B, portion of a panicle branch 
bearing spikelets; C, two views of a spikelet. 



382 



BURGER: FLORA COSTARICENSIS 383 

internodes glabrous, 3-4 mm. thick, hollow; nodes bearded or glabrous; leaf blades 15-28 
cm. long, 7-18 mm. wide, glabrous or sparsely pilose; ligule absent. Inflorescence 26-35 
cm. long, of 40-80 short ascending or spreading 1-sided spikelike racemes, mostly 1-5 (11) 
cm. long, the lower ones sometimes with secondary branches. Spikelets as in var. 
pilosum. Chromosome number n = 10 from a Costa Rican specimen. 

Moist forests; Finca la Taboga, Puerto Viejo. August to December. 
Previously known only from the Canal Zone. 

Hitchcock and Chase, in describing P. milleflorum, indicated that it 
was the same as Grisebach's P. distichum y lancifolium. Panicum 
milleflorum does not merit separate status as a species, being only a 
vigorous extreme of P. pilosum. Since Grisebach's name has priority 
at the varietal level, it must be used. 

Panicum polygonatum Schrad. in Schult., Mant. 2:256. 1824. Fig- 
ure 136. 

Duration indefinite, probably perennial; culms 25-110 cm. long, the bases long- 
decumbent and rooting at the nodes; branching freely from the rooted nodes and some- 
times from the middle nodes of erect culms; internodes 1.5-2.5 mm. thick, hollow, gla- 
brous or rarely pilose; nodes not prominent, usually retrorsely bearded; leaf sheaths 
shorter than the internodes, the overlapping edge ciliate, the surface glabrous, occasion- 
ally with scattered pilose hairs toward the apex; collar often pilose; ligule a minutely 
ciliolate membrane, 0.2-0.3 mm. long; leaf blades 5-25 cm. long, 8-15 mm. wide, the base 
cordate, length 5-9 x the width; pseudopetiole short, ca. 1 mm. long; surfaces glabrous 
or with a few pilose hairs on the upper surface above the ligule. Inflorescences terminal 
on leafy culms; panicles open, narrowly pyramidal, 10-25 cm. long, 3-11 cm. wide, the 
branches spreading or ascending, the lowermost remote, 3-11 cm. long, the upper 
branches shorter and closer; spikelets short-pedicellate in pairs or small groups along the 
lower sides of the triquetrous primary or secondary branches. Spikelets 1.3-1.9 mm. 
long, ovate 3.1-3.4:1, acute; plano-convex; first glume 0.5-1.0 mm. long, 1-3-nerved, 
ovate, acute; second glume 1.3-1.7 mm. long, 5-nerved, acute; lower (sterile) lemma 
1.2-1.5 mm. long, narrower than the glume, 3-nerved; upper (fertile) lemma 1.0-1.2 mm. 
long, elliptical 2-3:1, acute, stramineous; palea similar, flat; lodicules 2, truncate; anthers 
3, purple, 0.4-0.5 mm. long; styles 2, separate; stigmas purple; caryopsis ca. 0.8 mm. 
long, plump, tan. Chromosome number n = 20 from a number of Costa Rican specimens. 

Wet ditches, pond margins, along trails in wet forests; wet sites, 
mostly near both coasts; usually found from sea level to 300 m. eleva- 
tion, but occasionally to 1,300 m. June to August, occasionally during 
the remainder of the year. Southern Mexico to Paraguay. 

Panicum polygonatum is a member of the group Laxa, related to P. 
laxum and P. boliviense, but differing from both in the pointed 
spikelets and the lack of a palea in the sterile lemma. A single Costa 
Rican specimen, P. & D. 10679, from Laguna de Arenal, has conspicu- 
ously pubescent foliage and panicle branches bearing papillose-based 
cilia. It is otherwise similar to other Costa Rican specimens. 



384 FIELDIANA: BOTANY 

Panicum pulchellum Raddi, Agrost. Bras. 42. 1823. Figure 138. 

Duration indefinite, probably perennial; plants extensively creeping and rooting at the 
prostrate nodes, branching freely; erect portions of the culms 10-30 cm. long; prophylla 
prominently flanged, 5-15 mm. long; culm internodes less than 0.5 mm. thick, hollow, 
pilose or glabrous; nodes densely pilose-bearded; leaf sheaths shorter than the inter- 
nodes, more or less pilose to nearly glabrous; margins ciliate; collar bearded; ligule a 
minute membrane, 0.3-0.4 mm. long, ciliate or ciliolate; leaf blades flat, thin, obliquely 
cordate-ovate 3-4:1, 1.8-5.0 cm. long, 4-17 mm. wide; surfaces pilose to glabrous, often 
with purplish coloration. Peduncles included or exserted to 13 cm.; panicles solitary, 
terminal on erect portions of the culms, 4-16 cm. long, 2-4 cm. wide, of 6-25 ascending or 
drooping 1-sided spikelike racemes borne racemosely solitary or in pairs along the 
rachis; spikelets solitary or paired, short-pedicellate in 2 rows along the lower sides of 
the rachis. Spikelets finely pubescent, biconvex, acute, 2.0-2.3 mm. long; first glume 
0.9-1.2 mm. long, acute, 3-nerved, ovate 2:1; second glume 2.0-2.1 mm. long, 5-nerved; 
an evident internode between the first and second glumes; lower (sterile) lemma 1.9-2.0 
mm. long, 5-nerved, with a well developed palea 1.3-1.6 mm. long, rarely with 3 anthers 
0.8 mm. long; back of the sterile lemma usually bearing 2 circular flattened, eyelike 
glands above the middle, between the midrib and the first pair of lateral nerves; these 
may be absent, or 1-3 may occasionally be present; upper (fertile); floret 1.1-1.4 mm. 
long, ovate, the lemma smooth and shining, rigid; palea similar; anthers 3, yellow, 
0.6-0.7 mm. long; styles 2, separate; stigmas purple; caryopsis elliptical 2:1, 1 mm. long, 
white. Chromosome number n = 10 from Costa Rican and Venezuelan specimens. 

Occasional in moist forests, along trails, on forested roadsides, or in 
brush. Mostly on the Pacific slope, from San Mateo and San Ramon to 
Turrialba and southward to Canas Gordas; Meseta Central; La Virgen. 
Elevations from near sea level to 1,400 m. November to June. South- 
ern Mexico to Bolivia and Brazil; West Indies. 

Panicum rudgei Roem. & Schult., Syst. Veg. 2:444. 1817. Figure 
141. 

Caespitose perennial in dense clumps; culms 75-125 cm. long, erect, spreading, or 
scrambling in brush, branching freely from the upper nodes; internodes 1.5-3.0 mm. 
thick, hollow, more or less densely pilose; nodes densely pilose; sheaths densely pilose, 
longer or shorter than the internodes; ligule a short membranaceous rim, densely ciliate 
with stiff hairs, in total 1.5-2.0 mm. long; leaf blades rather stiff, pilose, 20-40 cm. long, 
caudate-acuminate, 8-14 mm. wide. Panicles terminal and axillary from the upper nodes, 
forming an elongated compound mass, 30-40 cm. long, half or a third as wide; pedicels, 
especially the terminal ones, much longer than the spikelets. Spikelets ovate, acuminate, 
3.0-3.4 mm. long, biconvex, the bracts gaping and exposing the fertile floret, hirsute 
toward the apex; first glume ovate, acuminate, 2.7-2.9 mm. long, 3-5-nerved; second 
glume 2.7-2.9 mm. long, 5-7-nerved; lower (sterile) lemma ca. 2.5 mm. long, 7-9-nerved, 
enclosing a palea of equal length and 3 stamens, the anthers deep purple, ca. 0.6 mm. 
long; upper (fertile) lemma 1.7-1.9 mm. long, rigid, elliptical 1.6-1.7:1, shining, 
stramineous; palea similar, flat; lodicules 2, truncate; anthers 3, deep purple, 0.8-0.9 
mm. long. The spikelets are unusual in having definite thick internodes, up to 0.5 mm. 
long between the glumes and between the florets. Chromosome number n = 9 from a 
Costa Rican specimen. 

This species is common on the savannas around Buenos Aires and 




FIG. 141. Panicum rudgei. A, culm with several panicles; B, C, two views of a 
spikelet; D, fertile floret. 



386 FIELDIANA: BOTANY 

occurs on the Boruca Savannas as well. Elevations 300-780 m. De- 
cember to April. Southern Mexico and Guatemala to Panama, Bolivia 
and Brazil. 

Panic-urn schiffneri Hack., Ergebn. Bot. Exped. Akad. Wiss. 
Suedbras. 11. 1906. 

Caespitose perennial, scrambling in brush, branching freely; internodes 1.5-3.0 mm. 
thick, solid or hollow with a small lumen, puberulent; leaf sheaths shorter than the 
internodes, the margin ciliate, the surface puberulent or glabrous; collar bearded; ligule 
a ciliolate membrane, ca. 0.5 mm. long; leaf blades flat, 12-15 cm. long, 13-20 mm. wide, 
ovate 7-10:1, the surfaces mostly glabrous; base of blades more or less asymmetric, 
rounded. Peduncles exserted 10-20 cm.; panicles 12-17 cm. long, terminal on leafy culms, 
very open, 12-16 cm. wide, the longest branch up to 10 cm. long; lower branches solitary 
and distant, naked below, the spikelets crowded on the outer third; upper branches 
much shorter; rachis and branches pilose; pedicels short. Spikelets 1.5-1.7 mm. long, 
elliptical-obovate 1.75-2.0:1, glabrous; first glume a minute nerveless cufflike scale, 
0.2-0.4 mm. long; second glume and lower (sterile) lemma equal, as long as the spikelet, 
5-nerved; lower floret lacking a palea; upper (fertile) floret broadly elliptical 3:2, blunt, 
rigid, somewhat flattened; lemma stramineous, finely striate, bearing scattered fine 
appressed hairs; palea similar; lodicules 2, truncate; anthers 3, orange, ca. 0.5 mm. long; 
styles 2, separate; stigmas purple; caryopsis 1.0 mm. long, oblong 1.5-2.0:1, tan. 

Rare in Costa Rica; known only by the following specimens: Prov. 
Alajuela, San Miguel de San Ramon, 21 August 1934. Brenes 19260. 
F.; Prov. San Jose, San Francisco de Guadalupe, 0. Jimenez s.n. Nov. 
1910 US (specimen determined by Chase, but material very in- 
adequate). Southern Mexico to Venezuela and Brazil; West Indies. 

Panicum sellowii Nees, Agrost. Bras. 153. 1829. 

Caespitose perennial from a hard, knotty crown; lower parts of the stems decumbent, 
rooting at the nodes; culms 100-150 cm. long, weak and scrambling in brush, branching 
freely, the branches divaricate; internodes 1-2 mm. thick, hollow, glabrous or finely 
pilose; nodes glabrous to pilose; leaf sheaths shorter than the internodes, or the upper 
ones overlapping, softly pilose to glabrous, the margin densely pilose-ciliate; ligule a 
minute membrane, 0.2-0.3 mm. long; collar and auricles pilose; leaf blades ovate 4-8:1, 
cordate-based, asymmetric, 6-12 cm. long, 7-18 mm. wide, nearly glabrous to velvety- 
pilose. Peduncles included or short-exserted; panicles terminal on leafy branches, 10-28 
cm. long, 4-16 cm. wide, ellipsoidal, very open; branches solitary or paired, straight, 
ascending or reflexed, the longest ones 5-14 cm. long, nearly simple, spikelet-bearing on 
the outer half, the spikelets mostly solitary, closely appressed to the branches. Spikelets 
obovate 2:1, acute, 2.0-2.3 mm. long, usually finely pubescent; first glume ovate 2:1, 
acute, usually 1-nerved, 1.2-1.5 mm. long; second glume shorter than the fertile floret, 
5-nerved, 1.8-2.0 mm. long; lower (sterile) lemma 5-nerved, 1.9-2.2 mm. long, containing 
a narrow, tongue-shaped hyaline palea 1.0-1.2 mm. long; upper (fertile) floret 1.6-1.9 
mm. long, obovate 1.5-2.0:1, acute, the lemma strongly convex, reddish brown, minutely 
roughened; palea similar, slightly convex; anthers 3, purple, 1.1 mm. long; styles 2, 
separate; stigmas purple; caryopsis elliptical 3:2, ca. 1.2 mm. long, white. Chromosome 
number n = 27 from a Costa Rican specimen. 



BURGER: FLORA COSTARICENSIS 387 

Brushy road embankments, bromeliad hedges, forest margins; ele- 
vations 600-1,700 m.; occasional; Grecia, Turrialba, Agua Caliente, 
Frailes, Rivas, Puriscal. July to November. Southern Mexico to 
Paraguay and Argentina; West Indies. 

Panicum sphaerocarpon Ell., Bot. S.C. & Ga. 125. 1821. 

Caespitose perennial in erect or sprawling tufts, lacking well-developed basal rosettes; 
culms 15-45 cm. long; internodes 1.0-1.5 mm. thick, hollow, glabrous, branching 
from the base and middle nodes; nodes glabrous or upwardly bearded; leaf sheaths 
longer or shorter than the internodes, glabrous except for fine pilose ciliation on the 
overlapping margin; ligule a sparse row of hairs, 0.3-0.7 mm. long; lower leaf blades 
shorter and broader than the uppermost ones; blades flat, cordate-based, firm-textured, 
glabrous except for a few stiff, pustulose-based elongated cilia on the rounded basal 
margins of the blades; lower leaf blades 3.0-6.5 cm. long, 8-11 mm. wide, 3-6 x longer 
than wide; upper blades 3-4 cm. long, 5-8 mm. wide, 4-6 x longer than wide. Peduncles 
of primary panicles 4-13 cm. long; primary panicles 4-7 cm. long, 3-4 cm. wide, ovoid or 
pyramidal, the spikelets borne on diverging pedicels; secondary panicles smaller, on 
shorter branches, their bases often included. Spikelets obovate ca. 1.8:1, brownish or 
purple, finely puberulent, 1.5-2.0 mm. long; first glume blunt, 0.4-0.7 mm. long, broader 
than long, usually 1-nerved; second glume 1.5-1.8 mm. long, 5-7-nerved; lower (sterile) 
lemma 1.5-1.7 mm. long, 5-7-nerved, enclosing a hyaline palea 0.7-0.9 mm. long; upper 
(fertile) floret 1.4-1.5 mm. long, broadly elliptical 1.5:1, ca. 1.5 mm. long, smooth and 
shining, stramineous; palea similar, slightly convex; lodicules 2, truncate; anthers 3, 
purple, 0.4 mm. long; styles 2, separate; stigmas purple; caryopsis broadly elliptical, 1 
mm. long, whitish, with a red spot at the base opposite the embryo. Chromosome 
number n = 9 from a Costa Rican specimen. 

Occasional; pastures and road embankments; middle elevations, 
mostly in the mountains south of San Jose; elevations 1,200-2,700 m.; 
Aserri, Tarbaca, Copey, Volcan Barba. Probably blooming yearlong. 
Eastern and southeastern United States, eastern Mexico to northern 
Panama; Venezuela, Cuba. 

This species belongs to the subgenus Dichanthelium, a group 
largely confined to temperate North America. The plants have two 
blooming periods, the secondary or axillary panicles produced later 
than the primary ones, and tending to have highly cleistogamous 
spikelets. In the tropical climates, the plants tend to lack the conspicu- 
ous basal rosettes of short, broad leaves that they exhibit in climates 
with a cold winter. Related species in our flora are P. laxiftorum, P. 
vistidellum, and P. olivaceum. 

Panicum stagnatile Hitchc. & Chase, Contr. U.S. Natl. Herb. 
17:528. 1915. 

This species has not as yet been collected in Costa Rica, but may be 
looked for in coastal swamps. 



388 FIELDIANA: BOTANY 

Panicum stenodes Griseb., Fl. Brit. W. Ind. 547. 1864. Figure 139. 

Short, densely tufted erect perennial, 15-40 cm. tall; culms unbranched, internodes 
less than 1 mm. thick, glabrous, hollow; nodes glabrous, inconspicuous; leaf sheaths 
short, glabrous to softly and densely pilose; ligule a minute membrane, 0.1-0.2 mm. long; 
leaf blades 2 or 3, flat or involute, 1-8 cm. long, 1.0-1.5 mm. wide, nearly glabrous to 
papillose-pilose. Peduncles included in the uppermost sheaths; panicles 1-5, exserted 
from the terminal sheath, 1-2 cm. long, each a slender racemose cluster of a few ap- 
pressed spikelets. Spikelets obovate 2:1, glabrous, 1.5-2.1 mm. long; first glume trian- 
gular 1:1, 0.9-1.2 mm. long, usually 3-nerved; second glume 1.4-1.8 mm. long, 5- 
(9-)nerved; lower (sterile) floret 1.3-1.8 mm. long, 5-7-nerved, with a hyaline palea ca. 
0.5-0.8 mm. long; upper (fertile) floret 1.2-1.7 mm. long, ovate 3:2, stramineous, rigid; 
palea equal, flat; anthers 2-3, deep purple, 0.4-0.6 mm. long; styles 2, separate; stigmas 
purple; caryopsis deep purple, elliptical, 0.8 mm. long. Chromosome numbers = 10 from 
a Costa Rican specimen. 

The delicate, wiry little plants may easily be overlooked. This 
species has been collected repeatedly on the savannas near Buenos 
Aires around the ponds. We have a recent collection from the road to 
Hacienda Las Animas, 2 km. E of the CIA. Dry savannas, elevations 
from 200-380 m. Probably blooming yearlong, but the inflorescences 
are very inconspicuous. 

The group Tenera of Hitchcock and Chase, to which this species 
belongs, is in need of revision. The exact number of species is debat- 
able. Specimens from Buenos Aires have been variously determined 
by Hitchcock and Chase as P. stenodes and P. stenodoides Hubb., 
although all material that I have seen is very similar. Panicum 
tenerum, which is considerably larger and has more pointed spikelets, 
has chromosome number n = 20. It has not yet been collected from 
Costa Rica. 

Panicum trichanthum Nees, Agrost. Bras. 210. 1829. Figure 142. 

Duration indefinite; plants scrambling in brush; culms up to 150 cm. long, branching 
freely, the lower portions prostrate and rooting at the nodes; internodes smooth and 
glabrous, hollow, 1.5-2.5 mm. thick; nodes glabrous, dark; prophylla up to 3 cm. long; 
leaf sheaths shorter than the internodes, glabrous except for the ciliate overlapping 
margin; ligule a minute membrane, 0.2-0.3 mm. long; leaf blades often with a short 
pseudopetiole up to 2 mm. long; blades cordate, narrowly ovate 4.5-8:1, 5.5-13 cm. long, 
8-23 mm. wide, pilose on the collar, mostly glabrous but occasionally finely pilose on the 
surfaces. Peduncles included or short-exserted; panicles terminal on leafy branches, 
open, dome-shaped, 17-27 cm. long, rather delicate, the spikelets borne on elongated 
flexuous pedicels. Spikelets obovate 2:1, biconvex, 1.2-1.6 mm. long; bracts covered with 
minute vesicles; first glume 0.2-0.4 mm. long, membranaceous, nerveless; second glume 
and lower (sterile) lemma about equal, as long as the spikelet; second glume 5-nerved; 
sterile lemma 3-5-nerved, with a narrow, tongue-shaped palea 0.7-0.8 mm. long; upper 
(fertile) floret ca. 1.1 mm. long, broadly ovate ca. 2:1, tan; palea similar to the lemma, 
convex; anthers 3, tan, 0.5-0.8 mm. long; caryopsis broadly oblong 4:3, ca. 0.8 mm. long, 
tan, opalescent. Chromosome number n = 18 from a Costa Rican specimen. 




FIG. 142. Panicum species. P. trichoides: A, blooming plant; B, two views of a 
spikelet; P. trichanthum: C, two views of a spikelet. 



390 FIELDIANA: BOTANY 

The plants clamber in brush or in marsh vegetation; occasional; 
Finca la Taboga, Lagunas de San Bernardo, Villa Neilly, Santa Rosa 
(Limon), Limon, Cahuita, Zhorquin. Near sea level to 550 m. eleva- 
tion, mostly near the coasts. Central Mexico to Paraguay; West Indies. 

This species is similar to P. trichoides in spikelet structure, but 
differs in size, leaf proportions, pubescence, and chromosome num- 
bers. 

Panicum trichoides Swartz, Prodr. Veg. Ind. Occ. 24. 1788. Figure 
142. 

Sprawling annual, the culms long-decumbent and rooting at the nodes, forming large 
patches; erect portions of the culms 10-80 cm. long; branching freely from both decum- 
bent and erect portions; internodes 1-2 mm. thick, hollow, pilose; nodes prominent, 
covered by the bases of the sheaths; prophylla 1.5-2.5 cm. long; leaf sheaths much 
shorter than the internodes, copiously papillose-pilose; ligule a short minutely ciliolate 
membrane, 0.2-0.3 mm. long; leaf blades thin and flat, obliquely cordate-ovate 3-5:1, 
3.5-7 cm. long, 5-19 mm. wide, more or less papillose-pilose, the lower margins 
papillose-ciliate. Inflorescences numerous, terminal on leafy branches; peduncles in- 
cluded or exserted up to 18 cm.; panicles broadly dome-shaped, 4-18 cm. long, 3-11 cm. 
wide, the longest branch 2-10 cm. long; panicles delicate, lacy, the small spikelets borne 
on thin, threadlike pedicels much longer than the spikelets. Spikelets obovate 2:1, 
1.2-1.3 mm. long, tapering to a slender base, plano-convex, rather thick; bracts finely 
pilose; first glume narrowly ovate, 0.6-0.7 mm. long, 1-3-nerved; an evident internode, 
ca. 0.2 mm. long between the first glume and the second; second glume slightly shorter 
than the spikelet, 1.1-1.2 mm. long, 3-5-nerved; lower (sterile) lemma 1.1-1.2 mm. long, 
3-5-nerved, enclosing a tongue-shaped hyaline palea 0.4-0.6 mm. long; upper (fertile) 
floret 0.9-1.0 mm. long, ovate 2:1, the lemma minutely roughened, tan, strongly convex; 
palea similar, flat; anthers 3, white, 0.4-0.5 mm. long; caryopsis obovate 2:1, 0.7-0.8 mm. 
long, opalescent, white. Chromosome number n = 9 from a Costa Rican specimen. 

Panicum trichoides is a common weed in wet, shaded sites at low 
elevations, from sea level to 600 m. elevation, rarely to 1,000 m., 
mostly near the coasts. Blooming mostly from June to October, but to 
some extent throughout the year. Mexico to Peru and Brazil; West 
Indies; Tropical Asia. 

This species is apparently most closely related to P. trichanthum. 

Panicum viscidellum Scribn., U.S.D.A. Div. Agrost. Circ. 19:2. 
1900. Figure 143. 

Perennial; culms 35-110 cm. long, the bases decumbent or rooting; culms erect or 
spreading, branching from the basal and middle nodes, sometimes producing dense tufts 
of small branchlets; internodes 1.5-2.0 mm. thick, hollow, papillose-pilose; nodes densely 
bearded with retrorse or spreading hairs; leaf sheaths shorter than the internodes, 
pilose; ligule a dense row of short white hairs, 0.5-1.0 mm. long, with much longer hairs 
on the upper leaf surface behind the ligule; leaf blades flat, soft, cordate-based, 5-12 cm. 
long, 8-20 mm. wide, more or less pilose on both surfaces. Peduncles exserted up to 22 
cm., terminal on the main culms or on leafy branches; primary panicles 5-11 cm. long, 3-9 




ye* 



FIG. 143. Panicum viscidellum. A, blooming culm; B, base of plant; C, two views of a 
spikelet. 



391 



392 FIELDIANA: BOTANY 

cm. wide, dome-shaped, rather dense; branches 1-several per node of the rachis; 
spikelets appressed along the primary or secondary branches; lateral pedicels ca. as long 
as the spikelets, the terminal ones much longer. Spikelets obovate 2:1, slightly acute, 
1.8-2.0 mm. long, finely pubescent; first glume 0.4-0.7 mm. long, obscurely nerved, ovate 
2:1, acute; second glume 1.6-1.9 mm. long, 7-nerved; lower (sterile) lemma 1.6-1.9 mm. 
long, 7-nerved, enclosing a hyaline palea 0.7-1.1 mm. long; upper (fertile) floret 1.6-1.9 
mm. long, elliptical 3:2, the lemma smooth and shining, rigid, apiculate; palea similar, 
flat; lodicules 2, truncate; anthers 3, 0.9 mm. long, purple; styles 2, separate; stigmas 
purple; caryopsis broadly elliptical 4:3, 1 mm. long, whitish, with a purplish stain near 
the base and a red spot near the base on the side opposite the embryo. Chromosome 
number n = 18 from Costa Rican specimens. 

Roadsides, river banks, in brush or oak forests; occasional on the 
Pacific slope, between 700 and 1,600 m. elevation; Volcan Rincon de la 
Vieja, Zapote (Prov. Alajuela); San Ramon area, Tarbaca, Tejar, 
lower slopes of the Cordillera de Talamanca. Probably blooming year- 
long, but primary panicles produced from June to January. Southern 
Mexico to Colombia. 

This species seems to belong to the subgenus Dichanthelium on the 
basis of its general morphology. Like other tropical species of this 
subgenus, it fails to make basal rosettes. Swallen (Fieldiana Bot. 
24:268. 1955) lists P. reflexopilum Steud., Syn. PI. Glum. 1:84. 1854. as 
a synonym of P. viscidellum. As this name far antedates P. viscidel- 
lum, it would have to be used if it could be firmly identified. No type 
material attributed to this name is in the U.S. National Herbarium, 
and the notes of Mrs. Chase indicate that she was unable to locate a 
type in Europe (personal communication from T. R. Soderstrom). The 
description seems to be applicable to P. viscidellum, but in the 
absence of a type, it seems inadvisable to change the name. 

EXCLUDED SPECIES 

Panicum altum Hitchc. & Chase, Contr. U.S. Natl. Herb. 17:488. 
1915. 

This sea coast species was reported from Buenos Aires (Tonduz 
3619). The specimen is immature and not identifiable. However, P. 
altum grows on coastal sand dunes, an entirely different habitat from 
the savannas of Buenos Aires. 

PARATHERIA Grisebach 

Panicle very slender, few-flowered; branches few, simple, strictly erect, deciduous at 
maturity, each bearing near its base a solitary appressed subsessile spikelet, the branch 
extending beyond the spikelet as a flattened bristle, tapering to a hispid apex; base of the 
branch forming an elongated sharp-pointed callus below the point of attachment of the 



BURGER: FLORA COSTARICENSIS 393 

permanently attached spikelet. Spikelets dorsally compressed, narrowly ovate, acumi- 
nate, remaining attached to the simple panicle branch and deciduous with it; glumes 
equal, blunt, much shorter than the spikelet; lower (sterile) lemma and upper floret 
about equal; sterile lemma membranaceous; upper (fertile) lemma stiff, acuminate, its 
margins thin, flat, covering the edges of the palea of similar texture. Lower leaf sheaths 
often swollen at the base and concealing a solitary cleistogene borne in the axil of an 
elongated membranaceous prophyllum. 

Paratheria is an anomalous panicoid genus, peculiar in its manner of 
disarticulation and spicate inflorescence. Authors of treatments of Af- 
rican grasses have placed the genus close to Pennisetum or Setaria 
because of the sterile, bristle-like branches. The spikelet morphology 
and cleistogamous habit appear most similar to the tropical American 
genus Reimarochloa. The distribution pattern of Paratheria is difficult 
to interpret, our species occurring in Cuba, Brazil, and tropical Africa, 
with another species described from Sierra Leone. (Panicoideae: 
Paniceae.) 

Paratheria prostrataGriseb., Cat. PL Cub. 236. 1866. Figure 143a. 

Duration indefinite; plants caespitose; culms prostrate or ascending, up to 60 cm. long, 
branching from the base and lower nodes; internodes hollow, glabrous; nodes densely 
upwardly bearded; prophylla membranaceous, 10-20 mm. long; leaves numerous; leaf 
sheaths keeled, the lowermost ones densely hirsute, the upper mostly glabrous except 
near the base; ligule a dense row of white cilia, 0.5-0.7 mm. long; dewlap hirsute; leaf 
blades flat, 1-3 cm. long, 2-3 mm. wide, the midrib keeled beneath; lower blades hirsute, 
the upper ones glabrous. Inflorescences terminal on the main culms or on leafy branches; 
lower leaf sheaths often swollen and concealing solitary cleistogamous fruitful spikelets 
(cleistogenes); peduncle and lower spikelets of terminal inflorescences included in the 
uppermost sheath. Inflorescence a spikelike panicle, 6-9 cm. long; branches solitary, 
simple, 1.5-3 cm. long, flattened or angular, strongly scabrous on the angles, tapering to 
an acute apex; solitary spikelet attached to the branch near the base on a short pedicel 
0.5-1.0 mm. long; branches deciduous from the rachis, the portion below the attachment 
of the spikelet forming a stiff, acuminate callus. Spikelets narrowly ovate 7-9:1, acumi- 
nate, dorsally compressed, 6-9.5 mm. long, glabrous except for a few hairs at the very 
base; glumes equal, membranaceous, blunt, nerveless, 0.5-0.7 mm. long, or absent from 
the cleistogenes; lower (sterile) lemma and upper (fertile) floret equally long; sterile 
lemma lacking a palea, ca. 10-nerved, with 3 closely spaced nerves near each margin; 
fertile floret with a stiff, smooth, 7-nerved lemma, its margins flat, covering the edges of 
a palea of similar texture; lodicules 2, truncate; anthers apparently 2, 2-4 mm. long in 
exserted spikelets, much smaller in the cleistogenes, mostly included, tangled with the 
stigmas; caryopsis obovate 8:3, blunt, 4.0-4.2 mm. long, tan; style base persistent; em- 
bryo conspicuous, ca. 2 mm. long; a red-brown spot at the base of the caryopsis opposite 
the embryo. 

This species was not previously reported from North or Central 
America. A recent specimen from Buenos Aires, cited below, is the 
first collection from Central America. Cuba, Dominican Republic; 
Brazil, Guyana, Colombia; tropical West Africa; Madagascar. Costa 
Rica: Prov. Puntarenas, Buenos Aires, Osa, elevation 385 m., ere- 



\ 





FIG. 143a. Paratheria prostrata. Plant, inflorescence, and spikelets. 

394 



BURGER: FLORA COSTARICENSIS 395 

ciendo en la orilla de una charca estacional, J. G. Laurito 2642, 5 
September 1977 (CR, ISC, F). 

PARIANA Aublet 

REFERENCES: J. R. Swallen, Eight new species ofPariana. J. Wash. 
Acad. Sci. 30:71-78. 1940. T. G. Tutin, A revision of the genus Pariana 
(Gramineae). J. Linn. Soc. Bot. 50:337-362. 1936. 

Perennial herbaceous grasses; caespitose, or rhizomatous but clump-forming; leaf 
blades mostly broad, borne on short pseud opetioles. Inflorescences mostly arising di- 
rectly from the soil on bladeless peduncles, rarely terminal on leafy culms; inflorescence 
a club-shaped rame of several to many internodes. Pedicellate staminate spikelets borne 
in verticels of 4-6 at each node of the rachis, the pedicels flattened, coriaceous, and often 
fused in pairs by their lateral margins; staminate spikelets composed of a pair of flat 
1-3-nerved glumes standing exterior to a dorsally compressed awnless floret; stamens 
2-many; a single sessile pistillate spikelet concealed within each verticel of staminate 
spikelets, its glumes herbaceous, equal, 1-nerved, covering the floret; lemma and palea 
indurate; stigmas 2, barely emerging from the whorl of staminate spikelets. 

Pariana is a small genus of herbaceous grasses of wet rain forests 
from Brazil, Bolivia, and Peru to Costa Rica. Although they are 
related to the bamboos, they do not form woody perennial culms. 
Because of their very shaded habitats and inconspicuous basal inflores- 
cences, they are probably overlooked by plant collectors. (Bam- 
busoideae: Parianeae.) 

Pariana parvispica Pohl, Iowa State J. Res. 47:73. 1972. Figure 
144. 

Perennial; rhizomatous, but the culms arising in clumps of few to many from one 
crown; sterile culms unbranched, arching, 35-50 cm. tall, 1-2 mm. thick, hollow; glabrous 
except for a single line of puberulence directly below the opening of the next sheath 
above; nodes densely puberulent with spreading trichomes; lower internodes 6-11 cm. 
long, bearing bladeless sheaths or small leaf blades, the sheath about one-third as long as 
the internode; foliage leaves grouped near the tips of the culms; crowded, with overlap- 
ping sheaths, the upper internodes 1-2 cm. long, the blades forming a flat spray, 
simulating a palm leaf; leaves bearing blades usually 6-13 per culm, their sheaths over- 
lapping, glabrous as a whole, but more or less puberulent along the margins near the 
apex; ligule minute, 0.2-0.3 mm. long, membranaceous, minutely ciliolate, blades of 
upper leaves 9-13 cm. long, 2-3 cm. wide, glabrous; pseudopetiole 1-2 mm. long, puberu- 
lent on its upper surface; auricles prominent, bearing abundant stiff dark bristles 6-12 
mm. long, inflorescences normally absent from leaf-bearing stems, but present on 
Davidse 1410, which bears basal aphyllous inflorescences and some apical ones on leafy 
culms. Inflorescence a thick, club-shaped spicate structure (rame), usually arising di- 
rectly from the soil, the peduncle bearing 2-3 bladeless sheaths, the uppermost sub- 
tending the inflorescence. Rame composed of several cylindrical segments ca. 9 mm. 
long; each internode bearing at its base a whorl of 3 erect flattened, cartilaginous 
pedicels, puberulent on their outer faces; pedicels overlapping and forming a continuous 
sheath around the thin, flattened rachis, nearly as long as the internode; 2 of the pedicels 




FIG. 144. Pariana parvispica. A, habit of plant, with basal inflorescence; B, a rame; C, 
single segment of a rame, with staminate spikelets at the apex; D, pistillate spikelet. 



396 



BURGER: FLORA COSTARICENSIS 397 

bearing paired staminate spikelets at their apex, the third with a single staminate 
spikelet. Each of the 2 sets of paired spikelets has only 3 glumes, 2 being placed at the 
free margins of the flat pedicel, the third between the 2 spikelets. Solitary spikelet 
similar to the paired ones, but with 2 equal glumes. Staminate spikelets consisting of the 
blunt, oblong, stiff, ciliate glumes, ca. 1 mm. long, standing external to a single floret; 
staminate floret dorsally compressed, awnless, oblong, ca. 1.5 mm. long, lemma puber- 
ulent, cartilaginous, very broad, facing outward, its margins inrolled around the edges of 
the palea; palea smooth, stiffish, 2-nerved, its margins inrolled; flower with 2 broadly 
spatulate lodicules, thickened above, ca. 1 mm. long; stamens 2, on thick, fleshy, short 
filaments; anthers slightly exserted through the tip of the floret at anthesis; pollen 
normal. Pistillate spikelet single at each node, completely concealed by the whorl of 
flattened pedicels, only the stigmas visible externally, ca. 8 mm. long, dorsally com- 
pressed, oval in cross section; glumes oblong, herbaceous, 1-nerved, enveloping the 
floret, glabrous except for the ciliolate margins; lemma and palea coriaceous, equal, 
tapering to a narrow herbaceous point; lemma very broad, its margins covering the 
edges of the palea, glabrous; lodicules 3, flat, vasculated, ca. 1-1.5 mm. long, bearing at 
their tips microhairs with 1, 2, or 3 cells; ovary slender, bottle-shaped, tapering into a 
stiff style; stigmas 2, short, rather sparsely hairy, extruded through the herbaceous 
tips of the lemma and palea and emerging from the whorl of pedicels at their apices. The 
terminal segment of the rame tapers to a point. It consists of 3 sterile flattened overlap- 
ping pedicels enveloping a single pistillate spikelet terminal on the end of the rachis. 
Chromosome number n = 11, from microsporocytes of Pohl & Davidse 11646. 

Rain forests, lowland Atlantic slope areas. Blooming occurs appar- 
ently only during the short-day season, probably from December to 
February. 

This is the most northerly species of the genus Pariana. It differs 
from all of the species of the genus described by Tutin and those 
described by Swallen in the small size of the inflorescences and various 
combinations of stamen number, pedicel length and union, and spikelet 
features. It is difficult to assign P. parvispica to any of the sections 
proposed by Tutin. At the type locality, the plants are abundant over a 
considerable area of undisturbed rain forest and along the margins of 
clearings. We have been able to cultivate the plants in the greenhouse, 
and the chromosome count was obtained from such cultivated plants. 
This is the species reported by Standley, Flora of Costa Rica 85 (1937) 
as P. zingiberina Doell, a South American species, on the basis of 
sterile material. 

PASPALIDIUM Stapf 

Rather succulent marsh or aquatic grasses, the culm bases often decumbent and 
rooting; inflorescences terminal or axillary from upper nodes; inflorescence a slender 
panicle composed of sessile one-sided racemes, borne singly or in pairs at the nodes of a 
triquetrous rachis; racemes slender, erect, bearing solitary spikelets in 2 rows along the 
lower sides of a triquetrous rachis that terminates in a reduced spikelet or a flattened, 
naked point. Spikelets dorsally compressed, ovate, acute, awnless, placed with the first 



398 FIELDIANA: BOTANY 

glume outward, the second glume turned toward the midrib of the rachis; first glume 
short, usually blunt; second glume nearly as long as the fertile lemma, which is exposed 
at the tip; lower (sterile) lemma flat, as long as the spikelet, containing a palea of equal 
length and usually a staminate flower with 3 anthers; upper (fertile) floret slightly 
shorter than the lower floret, its lemma elliptical, acute, rugulose, with a prominent 
areole above the base; margins inflexed over the keels of a similar palea. 

A small genus of about 12 species in warm climates, mostly in the 
Old World. The genus is most closely related to Brachiaria and 
Urochloa. (Panicoideae: Paniceae.) 

Paspalidium geminatum (Forsk.) Stapf, Fl. Trop. Africa 9:583. 
1920. Panicum geminatum Forsk., Fl. Aegypt.-Arab. 18. 1775. Fig- 
ure 145. 

Duration indefinite; culms 40-140 cm. long, erect, the bases often long decumbent and 
rooting; culms unbranched or rarely branched from the middle nodes; internodes gla- 
brous, 3-5 mm. thick, hollow, thick-walled, the wall containing numerous radial cham- 
bers separated by thin partitions, each filled with loose stellate parenchyma; nodes 
glabrous, often contracted; leaf sheaths mostly overlapping, glabrous; ligule a short 
membrane, densely ciliate, in total 0.7-2.7 mm. long; blades flat or somewhat inrolled, 
6-20 cm. long, 5-8 mm. wide, glabrous or minutely scaberulous above. Peduncle short, 
included; inflorescences terminal and sometimes axillary from the uppermost sheath; 
panicles 10-30 cm. long, very slender, the racemes appressed to the triquetrous rachis; 
lower racemes distant, up to 5 cm. long, the middle and upper ones progressively shorter 
and closer, sometimes paired and subopposite, the shortest upper ones less than 1 cm. 
long; rachis of racemes triquetrous, the angles minutely hirsute or scabrous, spikelet- 
bearing to the base; spikelets very short-pedicellate, in 2 rows alternating along the 
2 lower sides of the rachis. Spikelets disarticulating below the glumes, dorsally com- 
pressed, elliptical 1.5:1, acute, mostly 2.0-2.5 mm. long, rarely longer; first glume 
orbicular, 0.7-0.9 mm. long, thin, faintly 3-5-nerved or apparently nerveless; second 
glume shorter than the spikelet, 1.7-2.3 mm. long, 5-7-nerved, blunt, sometimes with 
cross-nerves near the apex; lower lemma 5-nerved, as long as the spikelet, with a palea 
of equal length and usually a staminate flower, the anthers ca. 1.2 mm. long, orange; 
upper floret rigid, the lemma 2.2-2.3 mm. long, elliptical 3:2-2:1, strongly rugulose; 
nerves 5, faint; palea of equal length and similar texture; anthers 3, 1.2-1.5 mm. long, 
orange; style branches separate, naked at the base; stigmas purple. Chromosome 
number n = 27 from one Costa Rican specimen. 

Coastal marshes; Taboga, Hacienda Palo Verde, Boca de Barranca; 
Rio Banano (Limon); elevations near sea level. August to February. 
Florida and Texas to Brazil and Peru; tropical Africa and Asia. 

Specimens with larger spikelets have been assigned to var. 
paludivagum (Hitchc. & Chase) Gould, Southw. Naturalist 15:391. 
1971, based on Panicum paludivagum H. & C., Contr. U.S. Natl. 
Herb. 15:32. 1910. Several of our specimens have spikelets approach- 
ing the size range of this entity. Chromosome numbers ranging from n 
= 9 to n = 27 have been reported for this species, and it is evident that 
the group is complex and perhaps not yet well understood. 




FIG. 145. Paspalidium geminatum var. geminatum: A, rooting base of culm and 
inflorescence; B, two views of a spikelet; var. paltidivagum: C, two views of a spikelet; 
D, fertile floret. 



400 FIELDIANA: BOTANY 

PASPALUM Linnaeus 

REFERENCES: D. J. Banks, Taxonomy of Paspalum setaceum 
(Gramineae). Sida 2:269-284. 1966. Agnes Chase, The North American 
species of Paspalum. Contr. U.S. Natl. Herb. 28:1-310 + XVII. 1929. 

Caespitose, rhizomatous, of stoloniferous annual and perennial grasses of extremely 
diverse size and habit. Inflorescence of 1 or more one-sided racemes, the spikelets 
short-pedicellate, borne in rows on the lower side of the rachis; spikelets mostly paired, 
the pairs alternating on opposite sides of the midrib, and the racemes hence 4-rowed, or 
solitary by absence or abortion of one member of each pair, and the racemes hence 
2-rowed. Intermediate conditions also occur, resulting in racemes in part 3-rowed. 
Rachis triquetrous, or flattened and sometimes winged, the midrib often prominent. 
Spikelets oriented with the first glume away from the midrib of the rachis and the second 
glume and the upper (fertile) lemma toward it. Spikelets more or less plano-convex, 
ovate, elliptical, or obovate in outline, blunt or acute; first glume present on some or all 
of the spikelets in some species, but absent in most; second glume and lower (sterile) 
lemma membranaceous, usually equal and as long as the spikelet, covering and conceal- 
ing the upper (fertile) floret; second glume covering all or most of the convex back of the 
fertile lemma, entirely absent in a few species; sterile lemma flat, covering the palea of 
the fertile floret, occasionally with a rudimentary or well-developed membranaceous 
palea and rarely with a staminate flower; fertile floret usually nearly as long as the 
spikelet; lemma stiff or rigid, its margins thick and more or less inrolled over the edges of 
a palea of equal length and similar texture; lodicules 2, truncate; anthers usually 3; styles 
2, separate, naked below; stigmas plumose; caryopsis elliptical or obovate, strongly 
dorsally flattened. The basic chromosome number in the genus is x = 10. 

Paspalum is a very large genus of grasses of warm climates, its 
center of diversity being in the American tropics. Relatively few 
species occur in the temperate zone. Estimates of the number of 
species range from 200 to 400. The ecological diversity of the genus is 
extreme. Some species are xeromorphic plants of dry savannas, while 
others occur in fresh water and salt marshes or as floating aquatics. 
The Central American species are all confined to low and moderate 
elevations, rarely above 2,000 m. Some species, as P. notatum and P. 
dilatatum, have forage value or are used for erosion control. Pas- 
palum conjugatum is a common weed and is regarded as a poor forage 
species. Paspalum paniculatum, P. candidum, and P. plicatulum are 
also common and weedy. The genus is related to Panicum, differing in 
its racemose rather than paniculate inflorescences. It is also similar to 
Paspalidium and Urochloa, which differ in having transversely corru- 
gated fertile lemmas, and to Axonopus and Brachiaria, which have 
the back of the fertile lemma turned away from the midrib of the 
rachis. Polyploidy and meiotic irregularities occur frequently. 
(Panicoideae: Paniceae.) 



BURGER: FLORA COSTARICENSIS 401 

KEY TO SPECIES OF Paspalum 

la. Spikelets (at least one of some pairs) possessing visible first glume 2 

Ib. Spikelets lacking first glume and sometimes lacking both glumes 8 

2a. Culms bearing single inflorescence on terminal peduncle, lacking axillary 

inflorescences 3 

2b. Culms bearing axillary as well as terminal inflorescences, sometimes several 

peduncles arising from terminal sheath 5 

3a. Tall, stout perennial, culms up to 3 m. tall; inflorescence a panicle of many racemes; 

spikelets over 3.5 mm. long P. fasciculatum 

3b. Plants less than 1 m. tall, slender; inflorescence of 2-7 racemes 4 

4a. Spikelets paired, racemes 4-rowed P. botterii 

4b. Spikelets solitary, racemes 2-rowed 46 

5a. Racemes one on each peduncle; sterile lemma usually with well-developed palea 

(see also P. setaceum) 6 

5b. Racemes several to many on each peduncle P. setaceum 

6a. Spikelets 2 mm. or less long 7 

6b. Spikelets 2.5 mm. or more long P. pilosum 

7a. Both spikelets of each pair with first glumes; spikelets 1.5-1.7 mm. long; racemes 

up to 3 cm. long P. decumbens 

7b. Lower spikelet of each pair with first glume, upper spikelet lacking one; spikelets 

1.7-2.0 mm. long; racemes 3-5 cm. long P. nutans 

8a. Second glume absent, spikelet consisting only of lower (sterile) lemma and 

fertile floret; back of fertile lemma completely exposed 9 

8b. Second glume present, covering all or most of back of fertile lemma ... 11 
9a. Racemes falling from central axis of inflorescence entire, with spikelets attached; 

spikelets whitish or green 10 

9b. Racemes persistent on plant, only spikelets falling; sterile lemma of spikelets yel- 
low or purple P. pulchellum 

lOa. Sheaths strongly scabrous; spikelets up to 2 mm. long P. scabrum 

lOb. Sheaths not scabrous; spikelets over 2 mm. long P. candidum 

lla. Rachis of individual racemes broad and thin, 2-8 mm. wide 12 

lib. Rachis of individual racemes less than 2 mm. wide 14 

12a. Low, stoloniferous plants of wet sites; foliage glabrous . . . P. acuminatum 

12b. Erect caespitose plants of dry savannas; foliage pubescent 13 

13a. Spikelets 4.5-6.7 mm. long, cordate at base; second glume strongly pectinate- 

ciliate, broadly winged; rachis 2.0-2.5 mm. wide P. pectinatum 

13b. Spikelets 3.0-3.2 mm. long, not cordate-based or winged; rachis 5-8 mm. wide 

P. stellatum 

14a. Mature fertile lemma stramineous 19 

14b. Mature fertile lemma reddish, chestnut-colored, or brown 15 

15a. Plants low, stoloniferous; spikelets 1.2 mm. or less long P. orbiculatum 

15b. Plants erect or sprawling, not stoloniferous; spikelets at least 1.5 mm. long . 16 
16a. Culms tall, stout, 80-250 cm. long; racemes 4-18 cm. long; spikelets 2.6-3.2 

mm. long, puberulent, apex with fringe of short hairs P. virgatum 

16b. Culms slender, 20-150 cm. long; racemes 3-6 (11) cm. long; spikelets 1.8-2.8 
mm. long, glabrous or appressed-pubescent, not fringed at apex 17 



402 FIELDIANA: BOTANY 

17a. Central part of sterile lemma with transverse wrinkles; anthers over 1 mm. long 

P. plicatulum 

17b. Central part of the sterile lemma flat, not wrinkled; anthers less than 1 mm. 
long 18 

18a. Spikelets appressed-pubescent, nearly circular in outline, length less than 1.3 
x width; spikelets usually paired, raceme 4-rowed P. convexum 

18b. Spikelets glabrous, obovate, length 1.3-1.5 x width; spikelets solitary, 
racemes 2-rowed P. centrale 

19a. Spikelets densely silky with long white hairs up to 6 mm. long borne on second 
glume; inflorescences large, fan-shaped, of numerous racemes 

P. saccharoides 

19b. Spikelets glabrous or pubescent, sometimes ciliate, but not concealed with long, 

white hairs; inflorescences various 20 

20a. Racemes falling from common rachis as units, with spikelets attached to 

flattened rachis; creeping or floating aquatic P. repens 

2Gb. Racemes persistent on common rachis, spikelets falling from axis; plants of 
wet or dry habitats 21 

21a. Spikelets 2 mm. or less long 22 

21b. Spikelets more than 2 mm. long 33 

22a. Spikelets 0.6-0.7 mm. long P. parviflorum 

22b. Spikelets at least 1 mm. long 23 

23a. Raceme solitary on each peduncle P. nutans 

23b. Racemes 2 or more on each peduncle (rarely 1 in depauperate individuals) ... 24 

24a. Racemes numerous (7-70), forming a panicle 25 

24b. Racemes usually 2-5, rarely solitary or as many as 8 26 

25a. Spikelets blunt or barely acute, length 1.4 x width or less; rachis of racemes 0.5 
mm. or less wide; racemes 18-70 per panicle P. paniculatum 

25b. Spikelets acute, length 1.5 x width or more; rachis of racemes 0.6-0.8 mm. wide; 

racemes 30 or fewer P. microstachyum 

26a. Plants strongly stoloniferous; racemes 2, conjugate, very slender; spikelets 

solitary, second glume silky-ciliate, especially toward apex P. conjugaium 

26b. Plants not stoloniferous; racemes 1-several; spikelets glabrous or pubescent 

but not silky-ciliate 27 

27a. Plants with solitary terminal inflorescences and lacking axillary inflorescences 28 

27b. Plants with terminal and axillary inflorescences from terminal sheaths and some- 
times from lower sheaths P. setaceum 

28a. Spikelets solitary, racemes 2-rowed 29 

28b. Spikelets paired, racemes 4-rowed 31 

29a. Spikelets bearing minute globular hairs; plants caespitose annuals P. multicaule 

29b. Spikelets glabrous; plants caespitose or rhizomatous perennials 30 

30a. Plants rhizomatous, forming open patches on wet mud 45 

30b. Plants densely caespitose, forming flat mats on soil P. pumilum 

3 la. Spikelets bearing minute glandular hairs; racemes paired (rarely 3) conjugate 

P. clavuliferum 

31b. Spikelets glabrous; racemes 1-6 32 

32a. Racemes 4-6; spikelets 1.5-1.8 mm. long P. squamulatum 



BURGER: FLORA COSTARICENSIS 403 

32b. Racemes 1-3; spikelets 1.0-1.1 mm. long; fertile lemma finely tuberculate 

P. pictum 

33a. Spikelets silky-ciliate 34 

33b. Spikelets glabrous or pubescent, but not conspicuously ciliate 36 

34a. Spikelets broadly ovate, length ca. 1.5 x width P. dilatatum 

34b. Spikelets ovate, acute, length at least 2.3 x width 35 

35a. Spikelets mostly paired, racemes 4-rowed; leaf blades ovate, cordate-based, 6-12 x 

longer than wide; racemes 1-5 P. humboldtianum 

35b. Spikelets solitary, racemes 2-rowed; leaf blades linear, usually 20-50 x longer than 

wide; racemes 8-33 P. fasciculatum 

36a. Spikelets 4.3-5.0 mm. long, acute, narrowly elliptical, at least 2.6 x longer 
than wide; rare; savannas of General Valley P. lineare 

36b. Spikelets less than 4 mm. long, variously shaped 37 

37a. Racemes usually 2, conjugate, sometimes a third below 38 

37b. Racemes 5 or more, borne along common rachis 42 

38a. Plants extensively stoloniferous, growing in wet areas 39 

38b. Plants erect or sprawling, but not stoloniferous; plants of various habitats 40 

39a. Spikelets glabrous; plants of sea beaches P. vaginatum 

39b. Spikelets with pubescent sterile lemmas; moist areas in interior . . P. distichum 

40a. Plants arising from thick, woody, scaly rhizomes; spikelets at least 3.5 mm. 
long P. notatum 

40b. Plants lacking rhizomes; spikelets less than 3 mm. long 41 

41a. Spikelets nearly circular, blunt; bracts tan, mottled, or streaked with brown 

P. serpentinum 

41b. Spikelets ovate, acute; bracts uniformly green or tan P. minus 

42a. Spikelets glabrous, solitary, racemes 2-rowed P. reclinatum 

42b. Spikelets pubescent or glabrous, paired, racemes 4-rowed 43 

43a. Racemes 5-8 in each inflorescence 47 

43b. Racemes 15-150 in each inflorescence 44 

44a. Culms erect, unbranched; basal leaf sheaths strongly keeled, closely overlap- 
ping, forming flat fans; spikelets obovate, ca. 1.5 x longer than wide, purple, 

glabrous or nearly so P. turriforme 

44b. Culms becoming branched; basal sheaths not strongly keeled; spikelets obo- 
vate, ca. 2 x longer than wide, mottled brown and tan, puberulent 

P. corypheum 
45a. Anthers pink, ca. 0.6 mm. long, sterile; endemic to Las Play it as del Rio 

Bebedero P. jimenezii 

45b. Anthers purple, 0.8-0.9 mm. long, producing pollen P. standleyi 

46a. Plants stoloniferous; spikelets acute, 2.7-3.2 mm. long P. distichum 

46b. Plants caespitose; spikelets blunt, less than 2 mm. long P. pumilum 

47a. Leaf blades ovate, widest near middle, 5-8 x longer than wide, 1-2.5 cm. broad; 

racemes 4-7 cm. long, rachis green; spikelets minutely appressed-pubescent 

P. cosiaricense 
47b. Leaf blades linear, 1 cm. or less wide; racemes 3-5 cm. long, rachis deep purple; 

spikelets glabrous or nearly so, purple P. tonduzii 



404 FIELDIANA: BOTANY 

Paspalum acuminatum Raddi, Agrost. Bras. 25. 1823. Figure 146. 

Duration indefinite, probably perennial; culms long decumbent and rooting from the 
lower nodes, often trailing in water; erect portions 35-65 cm. long; culms branching 
freely from the decumbent portions; internodes 1.0-1.5 mm. thick, solid, glabrous; nodes 
glabrous, not prominent; leaf sheaths shorter or longer than the internodes, glabrous; 
ligule a thin membrane, 1-2 mm. long, decurrent on the sheath margins; leaf blades 3-13 
cm. long, 4-12 mm. wide, glabrous, ovate, rounded abruptly to the base. Inflorescences 
terminal on leafy erect branches, occasionally axillary; peduncles included or exserted to 
5 cm.; racemes 1-5 on a short rachis; individual racemes 2.5-5.0 cm. long, borne on a 
short peduncle 1-2 mm. long; rachis flat, foliaceous, 2.5-3.0 mm. wide, scabrous on the 
margins, bearing a single protruding spikelet on the tip; spikelets alternating in 2 rows; 
pedicels short, angular. Spikelets strongly dorsally flattened, ovate 2.5:1, 3.2-4.0 mm. 
long, short-acuminate; first glume absent; second glume and lower (sterile) lemma equal, 
as long as the spikelet, thin and membranaceous, glabrous, 5-nerved, the lateral nerves 
paired and close to the margins; upper (fertile) floret 0.4-0.8 mm. shorter than the outer 
bracts, 2.4-3.0 mm. long, obovate 1.7-2.1:1, blunt, strongly dorsally flattened, stramine- 
ous, finely roughened, bearing a group of minute cilia at the apex; palea similar and of 
equal length, flat; lodicules 2, truncate; anthers 3, purple, 1.0-1.2 mm. long; styles 2, 
separate; stigmas purple. Chromosome number n = 20 from two Costa Rican specimens 
(reported originally as P. serratum). 

Province of Cartago, near Paraiso and Peralta; margins of shallow 
ponds; elevations 700-1,100 m. October to March. Louisiana and Texas 
to Argentina. 

This species and P. serratum H. & C. are very similar and differ 
mostly in vegetative vigor. I believe that all of our Central American 
specimens represent one species. We have abundant material from 
Honduras which matches the Costa Rican specimens in all respects but 
general vegetative size and vigor. 

Paspalum botterii (Fourn.) Chase, J. Wash. Acad. Sci. 13:436. 
1923. Dimorphostachys botterii Fourn., Mex. PI. 2:14. 1881. Figure 
147. 

Caespitose perennial from a knotty crown; plants 40-110 cm. tall; culms simple or 
sparingly branched; internodes 1-3 mm. thick, hollow, glabrous; nodes glabrous or 
appressed-bearded, dark; leaf sheaths mostly overlapping, keeled, sparsely to densely 
papillose-hispid, collar bearded, overlapping margin ciliate; ligule a thin brown mem- 
brane, 1.0-1.5 mm. long; a row of stiff elongate hairs just behind the ligule; larger leaf 
blades 17-44 cm. long, 12-24 mm. wide, ovate 9-23:1, the base of the blade usually 
cordate, sometimes the lower blades tapering to the base; blades flat, lax, more or less 
papillose-pilose on both surfaces; midrib broad, white, keeled beneath. Inflorescences 
terminal on leafy culms, 10-32 cm. long; panicle of 3-7 slender racemes borne racemosely 
along an angled central rachis; individual racemes ascending, 5-20 cm. long; rachis of 
racemes ca. 1.0 mm. wide, flat, the midrib not conspicuous, the margins raised, some- 
times ciliate; spikelets paired on each side of the midrib, crowded. Spikelets brownish, 
puberulent, 2.2-2.5 mm. long, obovate 1.4-1.6:1, blunt, dimorphic; first glume usually 
absent in the terminal spikelet of each pair, present or absent in the lower spikelet; first 
glume, when present, narrowly triangular, acute, 1-nerved, up to 1.6 mm. long; second 











FIG. 146. Paspalum species. P. candidum: A, inflorescence; B, two views of a 
spikelet; P. acuminatum: C, raceme apex with spikelets; P. repens: D, raceme apex 
with spikelets; P. reclinatum: E, raceme apex with spikelets. 



405 




FIG. 147. Paspalum botterii. Inflorescence, spikelets, fertile floret. 

406 



BURGER: FLORA COSTARICENSIS 407 

glume 3-5-nerved, slightly shorter than the fertile floret, which is exposed at the tip; 
lower (sterile) lemma as long as the spikelet, 3-5-nerved; upper (fertile) floret 2.2-2.4 
mm. long, elliptic-obovate; lemma whitish, finely striate, convex; palea similar, flat; 
anthers 3, purple, 0.7-1.0 mm. long; styles 2, separate; caryopsis (one individual) 1.2 
mm. long, elliptical 1.2:1, tan. Chromosome number n = 40 from Costa Rican specimens. 

Dry savannas, roadsides, forest margins, beaches; occasional in 
northern Guanacaste, mostly near the Pacific Coast; sea level to 250 m. 
elevation; Playas del Coco, Playa Tamarindo, Puerto Castillo, 
Hacienda Palo Verde, Bagaces, Finca la Pacifica. Blooming June to 
December. Central Mexico and Guatemala to northwestern Costa 
Rica. 

This species is similar to P. costaricense, from which it differs in the 
longer and narrower leaf blades, pubescent sheaths, the presence of a 
first glume, and in chromosome number. The species is named for 
Matteo Botteri. 

Paspalum candidum (Humb. & Bonpl.) Kunth, Mem. Mus. Hist. 
Nat. 2:68. 1815. Reimaria Candida Humb. & Bonpl. in Fliigge, 
Monogr. Paspalum 214. 1810. Figure 146. 

Sprawling or decumbent annual, the lower portions of the culms prostrate and rooting; 
upper portions erect or scrambling or leaning in brush; culms branching freely, espe- 
cially from decumbent nodes; internodes 1-2 mm. thick, hollow, thin-walled, glabrous; 
nodes dark, often prominent, rarely slightly pubescent; leaf sheaths glabrous or the 
overlapping margin finely ciliate; ligule a ciliolate, sometimes puberulent membrane, 
1-2.8 mm. long; leaf blades flat, thin, 4-10 cm. long, 8-21 mm. wide, broad-based, ovate 
3-5:1, tapering abruptly to an acute apex, glabrous to finely pilose on one or both 
surfaces. Peduncles terminal on leafy branches, included or exserted up to 5 cm.; rachis 
7-11 cm. long, flattened or triquetrous, glabrous or puberulent, bearing 6-23 ascending 
or drooping racemes, these 1-3 cm. long, falling as units from the rachis; racemes pilose 
at the base; rachis of racemes flattened, membranaceous, ca. 2 mm. wide, bearing 
spikelets from the base but extending beyond the terminal spikelet as a flat point; 
spikelets solitary, in 2 rows or occasionally 1 row, on very short pilose pedicels on the 
lower (abaxial) surface of the rachis and partially concealed by it. Spikelets whitish or 
rarely purplish, ovate-elliptical 1.8-2.1:1, blunt, 2.1-2.4 (2.7) mm. long; first and second 
glumes absent; lower (sterile) lemma flat, membranaceous, faintly 3-nerved; as long as 
the spikelet; upper (fertile) floret 2.0-2.3 (2.6) mm. long, the lemma smooth and shining, 
firm but not rigid; palea similar and of equal length, flat; lodicules 2, truncate; anthers 3, 
1.1-1.5 mm. long, yellow, sometimes suffused with purple near the base; styles 2, sepa- 
rate; stigmas dark. Chromosome number n = 30 from Central American specimens. 

Wet open or partially shaded areas; pastures, road ditches, 
cornfields, river banks; elevations 1,200-2,300 m.; common in the 
Meseta Central and occasional elsewhere at intermediate elevations in 
the mountains, Monteverde, Poas, Irazu, Cordillera de Talamanca. 
August to February. Southern Mexico to Chile. 

Paspalum candidum is the most common Costa Rican member of 



408 FIELDIANA: BOTANY 

the informal group Dissecta of Chase, which also includes, in our flora, 
P. scabrum, P. prostratum, P. reclinatum, and P. acuminatum. This 
group of species are mostly plants of wet habitats, having broad, 
foliaceous raceme rachises. Although all of our Central American 
chromosome counts for P. candidum indicate n = 30, counts from 
Venezuela of plants that are very similar morphologically indicate a 
diploid strain with n = 10 exists there. 

Paspalum centrale Chase, J. Wash. Acad. Sci. 17:145. 1927. Figure 
148. 

Plants caespitose, annual in cultivation, 30-85 cm. tall; culms erect or the bases 
decumbent, branching from the lower and middle nodes; prophylla 4-6 cm. long; inter- 
nodes 1.0-2.5 mm. thick, hollow, thick-walled, glabrous; nodes glabrous; leaf sheaths 
keeled, loose, usually longer than the internodes, sparsely to densely papillose-pilose; 
ligule a thin brown membrane, 3-4 mm. long; leaf blades linear, 9-24 cm. long, 3-11 mm. 
wide, sparsely to densely papillose-pilose; midrib keeled beneath; base slightly wider 
than the apex of the sheath; uppermost leaf blade reduced or obsolete. Peduncles ex- 
serted up to 5 (12) cm.; inflorescences terminal on leafy branches, 4-12 cm. long, the 
common rachis flattened and channeled, glabrous, 1.5-8 cm. long; racemes 1-9, solitary, 
racemose along the central rachis; individual racemes 2-6 (9) cm. long, with a tuft of 
elongate hairs at the base; rachis 1.0-1.3 mm. wide, zigzag, with a prominent midrib; 
spikelets usually solitary, in 2 rows, occasionally some of them paired and the raceme 3- 
or 4-rowed. Spikelets 2.0-2.5 mm. long, obovate 1.3-1.5:1, blunt, glabrous, grayish- 
green; first glume absent; second glume and lower (sterile) lemma equal, as long as the 
spikelet, thin, 4- or 5-nerved, the lateral nerves close to the margin, the sterile lemma 
smooth, not wrinkled as in P. plicatulum; upper (fertile) floret very slightly shorter than 
the spikelet, chestnut brown, plano-convex; lemma finely striate, the nerves evident; 
palea similar, flat; lodicules 2, truncate; anthers 3, yellow or purple-tipped, 0.8-0.9 mm. 
long; styles 2, separate; stigmas purple; caryopsis broadly elliptic, ca. 1.8 mm. long, 
dark-streaked, with a purplish spot opposite the embryo. Chromosome number n = 30 
from Costa Rican and Salvadorean specimens. 

Dry pastures, savannas, dry lake bed; sea level to 500 m. elevation; 
occasional in northwestern Guanacaste; Hacienda Murcielago, Finca 
La Cuera, Finca La Pacifica, Viente Siete, Puntarenas, Atenas. 
Blooming from July to October. Coastal El Salvador to Panama. 

This species is very similar to P. plicatulum, differing mostly in the 
broader rachis of the racemes, narrower spikelets, smooth sterile 
lemma, and annual habit. 

Paspalum clavuliferum Wright, Anales Acad. Ci. Med. Habana 
8:203. 1871. Paspalum pittieri Hack, in Beal, Gr. N. Amer. 2:88. 1896. 
Figure 149. 

Small caespitose annual in small tufts; plants 10-30 cm. tall, erect; culms branching 
from the base and middle nodes; internodes slender, less than 1 mm. thick, hollow, 
glabrous; nodes glabrous; prophylla 13-18 mm. long; foliage mostly crowded on the lower 




FIG. 148. Paspalum centrale. Inflorescence, spikelets. 
409 








FIG. 149. Paspalum species. P. clavuliferum: A, blooming plant; B, two views of a 
spikelet; P. multicaule: C, portion of a raceme; D, two views of a spikelet; P. 
parviflorum: E, inflorescence; F, two views of a spikelet. 



410 



BURGER: FLORA COSTARICENSIS 411 

half of the culms; leaf sheaths more or less papillose-pilose, especially on the margins; 
ligule a thin, brown membrane, 0.7-1.0 mm. long; leaf blades flat, 3-9 cm. long, 1.5-3.0 
mm. wide, the midrib prominent beneath; surfaces papillose-pilose, prominently ciliate; 
uppermost sheath bearing a reduced or abortive blade. Peduncles terminal and axillary 
from the upper sheaths, the terminal one very slender, exserted 10-13 cm. beyond the 
uppermost developed leaf blade, bearing a bladeless sheath; inflorescence a solitary 
raceme or a conjugate pair at the summit of the peduncle, occasionally a third raceme 
below them; individual racemes 1-4 cm. long, arcuate, the rachis triquetrous, 0.4-0.5 
mm. wide; spikelets paired, 4-rowed, the pedicels less than 0.5 mm. long, puberulent. 
Spikelets 1.2-1.4 mm. long, obovate 3:2, blunt; first glume absent; second glume and 
lower (sterile) lemma equal, as long as the spikelet, hyaline, 3-nerved; second glume 
usually more or less pubescent with minute, capitellate hairs; sterile lemma usually 
glabrous or with a few capitellate hairs on the margins; both bracts sometimes with 
minute brownish splotches; rarely the spikelets may be entirely glabrous; upper (fertile) 
floret about as long as the spikelet, obovate, the lemma and palea stiff, finely striate; 
anthers 3, tan, 0.2-0.3 mm. long; caryopsis obovate 4:3, blunt, 0.8 mm. long, tan. 
Chromosome number n = 10 from a Costa Rican specimen. 

Occasional on dry tuff outcrops, savannas, and sea cliffs, mostly in 
northern Guanacaste, rare elsewhere. Hacienda Murcielago, Las 
Animas, Playas del Coco, Piedades de San Ramon. August to De- 
cember. Southern Mexico to Honduras; Costa Rica to northern South 
America to Brazil; West Indies. 

Plants in the same collection may have densely pubescent or gla- 
brous spikelets. The presence of trapped anthers in spikelets contain- 
ing mature caryopses suggests that this species is highly cleistogam- 
ous, which may account for the presence of glabrous and pubescent 
strains in close proximity. 

Paspalum conjugatum Bergius, Acta Helv. Phys.-Math. 7:129. 
1762. Figure 150. 

Strongly stoloniferous perennial; flowering culms arising from the rooted stolons, 
20-100 .cm. long, simple or branching from the lower nodes; internodes 1-3 mm. thick; 
glabrous, shrunken in drying; nodes mostly glabrous or rarely appressed-bearded; leaf 
sheaths more or less compressed, usually glabrous except for the finely ciliate overlap- 
ping margin; sometimes both margins hyaline and glabrous; ligule a hyaline membrane, 
0.3-1.5 mm. long; leaf blades 7-20 cm. long, 7-14 mm. wide, the upper surface sparsely to 
densely pilose; collar minutely bearded; blades of stolons ovate, blunt, 2-4 cm. long, 5-8 
mm. wide. Peduncles terminal on leafy culms, included or exserted up to 7 cm.; inflores- 
cence of 2 conjugate slender divergent or reflexed racemes, rarely a third raceme borne 
below them on vigorous plants; individual racemes 6-16 cm. long; spikelets solitary, in 2 
rows, closely placed; rachis 0.7-0.9 mm. wide, the tip often bearing several minute 
abortive spikelets; pedicels 0.3-0.4 mm. long. Spikelets strongly flattened, 1.3-1.9 mm. 
long, elliptic-ovate 1.2-1.4:1, scarcely pointed; first glume absent; second glume and 
lower (sterile) lemma equal, as long as the spikelet, hyaline, both with 2 marginal 
nerves, lacking midribs; second glume finely ciliate with hairs up to 1 mm. long; lower 
lemma similar but not ciliate; upper (fertile) floret ca. as long as the spikelet, whitish, 




FIG. 150. Paspalum conjugatum. Blooming plant with a stolon, two views of a 
spikelet, fertile floret. 



412 



BURGER: FLORA COSTARICENSIS 413 

firm but not rigid, the lemma slightly convex, the palea flat; anthers 3, yellow, some- 
times purple-splotched, ca. 0.6 mm. long; styles 2, separate; stigmas dark; caryopsis 
1.0-1.1 mm. long, elliptical 1.3:1, tan, the persistent styles reflexed along the sides of the 
caryopsis. Chromosome number 2n = 40 from Costa Rican specimens. 

A common weed in moist pastures, road ditches, marshes, beaches, 
cafetales, etc. On both Pacific and Caribbean slopes, from sea level to 
1,200 m. elevation. Blooming yearlong. Southern United States to 
Argentina; naturalized in the tropics of the Old World. 

This species is weedy and aggressive in wet pastures. It is almost 
universally regarded with disfavor and said to be rejected by livestock 
and to increase under grazing conditions. Common name Turvurd or 
Turbard. Our slides showed no pairing in meiosis, and it may be that 
the species, which is highly uniform in aspect, is completely apomictic. 
Several minor variants have been described, but my measurements 
show complete intergradation in spikelet and leaf blade size. Such 
variation as occurs appears to be related to fertility and moisture 
supply. 

Some authors have ascribed the name of this species to Swartz, on 
the basis that the original publication by Bergius was a phrase name. 
However, Bergius gives the name as "PASPALUM (conjugatum) 
spicis conjugatis." His usage differs from that of Linnaeus, who placed 
the "trivial" name in the page margin, whereas Bergius placed it after 
the generic name but in parentheses. His intent seems clear, and there 
is no reason to reject his authorship. The identity of the plate accom- 
panying the description is conclusive. 

Paspalum convexum Humb. & Bonpl. in Fliigge, Monogr. Pas- 
palum 175. 1810. Figure 151. 

Caespitose annual, the culms prostrate to ascending, 10-60 cm. long, the plants often 
mat-forming; culms branching freely from base and lower nodes, the branches some- 
times fascicled; culms 1.0-1.5 mm. thick, the internodes usually shrunken in drying, 
glabrous; nodes glabrous; leaf sheaths loose, keeled, glabrous to densely papillose-pilose; 
ligule a thin brown membrane, 1-2 mm. long; leaf blades flat, rounded to the base, the 
midrib prominent beneath, usually 5-18 cm. long, 5-9 mm. wide, from densely papillose- 
pilose to nearly glabrous; uppermost blade usually very reduced. Peduncles included or 
exserted up to 7 cm.; inflorescences terminal on the main culm or on leafy branches, 4-8 
cm. long, composed of 1-5 solitary racemes borne along a central rachis; individual 
racemes 3-5 cm. long; rachis ca. 1 mm. wide, with a tuft of long white hairs at its base; 
spikelets crowded, usually paired on each side of the midrib, in occasional individuals one 
spikelet of the pair abortive and the raceme thus appearing 2-rowed. Spikelets 1.8-2.5 
mm. long, obovate to subcircular 1.3-1.0:1, strongly plano-convex, the depth nearly 
equal to the width; first glume absent (present in one abnormal individual); second glume 
nearly as long as the spikelet, 5-7-nerved; lower (sterile) lemma as long as the spikelet, 
5-nerved, both bracts very thin and membranaceous, bearing scattered fine appressed 




FIG. 151. Paspalum convexum. A, blooming plant; B, portion of a raceme; C, two 
views of a spikelet. 



414 



BURGER: FLORA COSTARICENSIS 



415 



hairs; occasional individuals have a rigid, convex, shiny brown sterile lemma, similar to 
the fertile lemma; upper (fertile) floret nearly as long as the spikelet, the lemma very 
strongly convex, shiny, striate, chestnut brown; palea similar, flat; lodicules 2, truncate; 
anthers 3, purple, 0.8-1.1 mm. long. Chromosome numbers n = 10, 16, 20, 24 from 
Central American and Venezuelan specimens. 

This species is a weedy, sprawling annual of disturbed sites, road- 
sides, ditches, savannas, sea cliffs; common at lower elevations in 
northwestern Guanacaste and in the lower General Valley; occasional 
in the western portions of the Meseta Central. Elevations sea level to 
600 m., rarely to 1,400 m. Blooming mostly July to January. Northern 
Mexico to Brazil; West Indies. 

This species shows considerable variation in size, pubescence, and 
inflorescence and spikelet characteristics. It also has meiotic and 
chromosomal abnormalities. Paspalum convexum was assigned to the 
informal group Plicatula by Chase, along with P. plicatulum and 
P. centrale. 

Paspalum corypheum Trin., Gram. Pan. 114. 1826. Figure 152. 

Caespitose perennial from hard knotty crowns; culms 65-400 cm. long, erect or 
scrambling in brush, branching freely when older; internodes 2-4 mm. thick, hollow, 
glabrous or appressed-pilose, especially below the nodes; nodes densely bearded with 
appressed or spreading hairs; leaf sheaths keeled, mostly overlapping, the lower ones 
pustulose-hispid, the upper ones less pubescent; overlapping margin ciliate; collar con- 
spicuously bearded; ligule a firm brown membrane, 1.0-4.5 mm. long; leaf blades flat, 
usually 30-50 cm. long, 10-13 mm. wide, tapered to a narrow or cordate base; a dense tuft 
of long, glassy hairs just behind the ligule, surfaces glabrous or puberulent, midrib 
conspicuous, white, edges strongly scabrous, sometimes papillose-ciliate; uppermost 
sheath bladeless or with a short abortive blade. Peduncles terminal on leafy branches, 




FIG. 152. Paspalum corypheum. Portion of inflorescence, two views of a spikelet, 
fertile floret. 



416 FIELDIANA: BOTANY 

exserted up to 18 cm.; inflorescence 8-24 cm. long, of 15-44 racemes borne singly or 
whorled along a scabrous-angled central rachis; individual racemes 5-13 cm. long, the 
rachis ca. 0.5 mm. wide, bearing a tuft of stiff white elongate hairs at its base, sometimes 
a few scattered hairs along its length; spikelets paired, in 2 rows on each side of the 
midrib. Spikelets 2.0-2.5 mm. long, obovate ca. 2:1, acute; first glume absent; second 
glume nearly as long as the spikelet, 3-nerved, brownish and speckled with fine 
papillose-based hairs; lower (sterile) lemma similar, 3-nerved, as long as the spikelet, 
glabrous or sparsely hairy; upper (fertile) lemma nearly as long as the spikelet, whitish, 
finely striate; palea similar, flat; lodicules 2, truncate; anthers 3, deep purple, 1.2-1.4 
mm. long; styles 2, separate; stigmas deep purple. Chromosome number n = 30 from a 
specimen from Honduras. 

Dry, rocky Curatella-Byrsonima savannas, from the La Cruz area 
to Canas; elevations 75-300 m. July to August. Belize and Honduras; 
Costa Rica and Panama and northern South America to Brazil; 
Trinidad. 

Our specimens apparently represent this species in an early bloom- 
ing stage, before branching has occurred. Chase indicates that the 
plants may become much longer and more branched with age, and that 
the panicle branches may droop. The spikelets of P. corypheum are 
rather similar to those of P. botterii, but lack any evidence of the first 
glumes present in the latter species. 

Paspalum costaricense Mez, Fedde, Repert. Sp. Nov. 15:72. 1917. 
Figure 153. 

Caespitose perennial, the small clumps arising from a knotty crown; culms un- 
branched, 30-75 cm. tall, 2-3 mm. thick, hollow, glabrous; nodes glabrous; leaf sheaths 
overlapping, glabrous except for the finely ciliate overlapping margin; ligule a thin 
brown membrane, 3-5 mm. long; leaf blades thin, flat, lax, ovate-obovate 5-8:1, usually 
10-18 cm. long, 15-30 cm. wide, abruptly acuminate; midrib white, prominent; base 
rounded; margins short-ciliate; surfaces usually glabrous, rarely with a few short hairs 
near the margins; terminal sheath with a much reduced or abortive blade. Peduncles 
solitary, terminal on leafy culms, exserted up to 9 cm. from the terminal sheath; inflores- 
cence 6-13 cm. long, an open raceme of 5-7 solitary, ascending racemes borne singly 
along a flattened rachis; individual racemes 4-7 cm. long, their rachis flattened, 0.6-1.0 
mm. wide, with a low midrib; base of each raceme with a tuft of elongate glassy hairs; 
spikelets paired, in 2 rows on each side of the midrib; pedicel of the terminal spikelet of 
each pair 1.0-1.5 mm. long, that of the lower spikelet ca. half as long. Spikelets 2.4-2.8 
mm. long, elliptical-obovate 1.7-2.0:1, barely acute; first glume absent; second glume and 
lower (sterile) lemma equal, as long as the spikelet, very finely appressed-pubescent to 
nearly glabrous, thin, 3-5-nerved, brownish or purple-splotched; upper (fertile) floret 
elliptic-obovate, 2.2-2.5 mm. long, stramineous, finely striate; lemma convex; palea 
similar, flat; anthers 3, 0.9-1.0 mm. long, dark; styles 2, separate; stigmas dark; cary- 
opsis elliptic 1.4:1, tan, 1.9 mm. long; embryo large, a brownish stripe at the base of the 
caryopsis opposite the embryo. Chromosome number n = 30 from a Costa Rican 
specimen. 

Moist, partially shaded sites; roadsides, brush, banana fields. 




FIG. 153. Paspalum costaricense. A, plant base; B, culm and inflorescence; C, two 
views of a spikelet. 



417 



418 FIELDIANA: BOTANY 

Meseta Central, 1,100-1,700 m. elevation; San Jose area, Aserri, Tar- 
baca, Copey. The type specimen was collected near the San Jose Rail- 
road Station. Apparently blooming yearlong, but most specimens have 
been collected from June to August. Guatemala, Honduras, El Sal- 
vador, Costa Rica. 

The very broad, lax leaf blades of this species are distinctive. 

Paspalum decumbens Swartz, Prodr. Veg. Ind. Occ. 22. 1788. 

Duration indefinite, probably perennial; plants decumbent, forming mats, rooting 
from the nodes of prostrate portions; erect leafy branches 15-40 cm. long; prophylla 10-20 
mm. long; internodes 1.0-1.5 mm. thick, hollow, glabrous; nodes often ciliate; leaf 
sheaths keeled, finely ciliate on the overlapping margin, the surface glabrous or softly 
pilose; ligule a thin brown membrane, 0.3-0.5 mm. long, sometimes forming an auricle; 
leaf blades ovate 4.5-10:1, acuminate, 3-7 cm. long, 7-12 mm. wide, flat, the midrib 
prominent beneath; base cordate, contracted into a short pseudopetiole; margins ciliate, 
surfaces more or less pilose. Peduncles 1-6 from the uppermost sheath, very slender, 
exserted up to 7 cm., more or less pilose, especially toward the apex; inflorescence a 
solitary arcuate raceme, 7-30 mm. long; rachis ca. 0.5 mm. wide, its margins slightly 
raised and incurved, sometimes bearing scattered elongate hairs; pedicels scabrous, the 
members of each pair equal, forked from the base; spikelets paired, in 4 rows, crowded. 
Spikelets 1.5-1.7 mm. long, glabrous, broadly obovate 1.2-1.4:1, strongly plano-convex; 
first glume a broad, truncate nerveless scale, 0.2-0.4 mm. long; second glume broadly 
ovate, blunt, 1.1-1.2 mm. long, 3- or rarely 5-nerved, the lateral nerves not close to the 
margins; lower (sterile) lemma as long as the spikelet, 3-nerved, the lateral nerves 
marginal; lemma enclosing a well-developed, 2-nerved flat palea 1.1-1.4 mm. long; fertile 
lemma 1.4-1.5 mm. long, the upper half of the back exposed; surface striate, whitish; 
palea similar, flat; lodicules 2, truncate; anthers 3, 0.6-0.8 mm. long, usually white; styles 
2, separate; caryopsis suborbicular, ca. 0.9 mm. long, plano-convex, tan. Chromosome 
number n = 10 from Costa Rican specimens. 

Moist forests and forest margins, brush, riverbanks, roadsides and 
ditches, road embankments; sea level to 1,200 m. elevation; common in 
moist areas on both Pacific and Caribbean slopes; absent from drier 
parts of Guanacaste. Blooming yearlong. Guatemala to Brazil and 
Bolivia; West Indies. 

This rather weedy species is highly unusual in its genus by possess- 
ing not only first glumes but a well-developed palea in the sterile 
lemma. This species is most closely related in our flora to P. nutans, a 
tetraploid with longer racemes and larger spikelets. 

Paspalum dilatatum Poir., Lam. Encycl. 5:35. 1804. 

Caespitose perennial; culms arising from short, densely scaly rhizomes; plants up to 
175 cm. tall, the culms ascending and arching, simple or rarely branched from lower 
nodes; prophylla up to 15 cm. long, prominent; internodes oval, 2-4 mm. thick, hollow, 
glabrous; nodes swollen, sparsely appressed-pubescent; leaf sheaths longer or shorter 
than the internodes, loose, keeled, the lowermost ones more or less appressed-pilose 
with weak hairs; upper sheaths glabrous; margin glabrous; ligule a firm brown mem- 



BURGER: FLORA COSTARICENSIS 419 

brane, 1-5 mm. long; leaf blades linear, up to 52 cm. long, tapering to a narrow base, up 
to 10 mm. wide, glabrous except for a few long hairs on the basal margins; midrib keeled 
below, white; blades flat, folded near the base. Peduncles slender, solitary, exserted up 
to 30 cm.; inflorescence usually of 3-5 solitary racemes borne racemosely along a flat- 
tened rachis up to 9 cm. long; individual racemes arcuate, drooping, 3-10 cm. long, with a 
tuft of long silky hairs at the base; rachis 1.0-1.3 mm. wide; spikelets paired in 2 rows on 
each side of the low midrib. Spikelets strongly dorsally flattened, ovate 1.5-1.6:1, acute, 
3.1-3.7 mm. long; first glume absent; second glume and lower (sterile) lemma herba- 
ceous, 5-7-nerved, both exceeding the upper (fertile) floret and flattened beyond its tip; 
second glume slightly longer than the sterile lemma, bearing a prominent marginal 
fringe of soft, fine hairs; sterile lemma similar but with fewer cilia; surfaces of both 
bracts with scattered fine appressed hairs; upper (fertile) floret broadly ovate 1.2-1.3:1, 
blunt, the lemma stramineous, finely striate, strongly flattened; palea similar, flat; 
lodicules 2, truncate; anthers 3, 0.9-1.4 mm. long, deep purple; styles 2, separate; stig- 
mas purple; caryopsis (one seen) 1.3 mm. long, elliptical, tan, with a longitudinal brown 
mark opposite the embryo. Chromosome number 2n = 50 determined from Costa Rican 
collections. 

Roadsides, pastures, meadows; occasional on the volcanoes of the 
Cordillera Central, 1,900-2,600 m. elevation; Vara Blanca, Volcan 
Poas, Volcan Turrialba. Native to southern South America and prob- 
ably introduced to Costa Rica as a forage plant; now widely distributed 
as a wild and cultivated plant in the southern United States and in 
many other warm temperate and tropical parts of the world. Meiosis in 
our plants was irregular and the plants are apomictic. 

Paspalum distichum L., Syst. Nat. ed. 10, 2:855. 1759. P. pas- 
paloides (Michx.) Scribn., Mem. Torrey Bot. Club 5:29. 1894. Figure 
154. 

Extensively rhizomatous and stoloniferous perennial; erect portions of the culms 12-30 
cm. long, simple; internodes up to 2 mm. thick, solid, glabrous; nodes appressed- 
pubescent, somewhat swollen; leaf sheaths loose, keeled, glabrous to papillose-pilose, 
especially at the nodes, throat, and collar; ligule a thin brown truncate membrane, 
0.4-1.5 mm. long; leaf blades 2.5-10.0 cm. long, 3-6 mm. wide, usually glabrous except for 
the papillose-ciliate lower margins, rarely finely pilose above, often folded. Peduncles 
included or exserted up to 4 cm.; inflorescences terminal on the ascending or erect culms, 
consisting usually of 2 racemes, the lower one sessile or subsessile, the upper one borne 
on a rachis 5-10 mm. long; sometimes a third raceme borne below the terminal pair; 
individual racemes 1-6 cm. long, the flattened rachis 1-2 mm. wide, with a prominent 
midrib; a solitary spikelet borne at the tip of the rachis; spikelets solitary, in 2 rows. 
Spikelets very short-pedicellate, 2.7-3.2 mm. long, obovate 1.9-2.4:1, strongly dorsally 
flattened; first glume absent or, if present, deltoid to linear, 1-nerved, up to 1.9 mm. 
long, highly variable in one inflorescence; second glume and lower (sterile) lemma equal, 
as long as the spikelet, 3-5-nerved; glume glabrous, the lemma appressed-pubescent 
with fine hairs; sterile lemma enclosing a rudimentary, usually bifurcate, membrana- 
ceous palea, up to 1 mm. long; upper (fertile) floret ca. 2.7 mm. long, the lemma flat- 
tened, whitish, finely striate, firm but not rigid; palea similar, flat; lodicules 2, truncate; 
anthers 3, deep purple, 1.3-1.5 mm. long; styles 2, separate; stigmas deep purple. 
Chromosome number n = 30 from Costa Rican specimens. 




FIG. 154. Paspalum species. P. distichum: A, two views of a spikelet; P. vaginatum: 
B, blooming culm; C, rhizomatous base; D, two views of a spikelet. 



420 



BURGER: FLORA COSTARICENSIS 



421 



Occasional, wet roadside ditches, wet pastures, margins of irrigation 
ditches; mostly at intermediate elevations in the interior, from 1,000- 
1,500 m. elevation. Monteverde, Birri, Meseta Central, Cartago, Juan 
Vinas, Liverpool. June to November. Southern United States, north- 
ward to New Jersey and Washington near the coasts, southward to 
Argentina and Chile; West Indies; Eastern Hemisphere in warm 
areas. 

This species is confined mostly to the interior of Costa Rica, whereas 
the very similar P. vaginatum occurs only on the coasts. Tetraploids 
(n = 20) have been reported from other regions. Recent nomenclatural 
arguments as to the identity of the Linnean type material have been 
advanced by Fosberg (Rhodora 78:84. 1976) and Guedes (Taxon 
25:512-513. 1976), who come to contradictory conclusions as to the 
name of this taxon. I have followed Guedes, who uses the name in the 
traditional sense. 

Paspalum fasdculatum Willd. in Fliigge, Monogr. Paspalum 69. 
1810. Figure 155. 

Tall, coarse stoloniferous perennial, forming dense colonies; bases trailing and rooting 
up to 5 m.; erect culms simple or sparingly branched, to 3 m. tall; internodes glabrous, 
3-7 mm. thick, solid; nodes swollen, the sheath base covering the node glabrous to 
copiously bearded; leaf sheaths shorter or longer than the internodes, glabrous or 




FIG. 155. Paspalum fasdculatum. Inflorescence, two views of a spikelet, fertile 
floret. 



422 FIELDIANA: BOTANY 

pustulose-hispid, especially near the base and apex; overlapping margin long-ciliate with 
fine hairs; ligule a firm brown membrane, 0.3-0.7 mm. long, a row of stiff white hairs, 3-4 
mm. long behind it; leaf blades flat, keeled beneath, 20-70 cm. long, 10-20 mm. wide; 
surfaces glabrous to sparsely pilose, often with elongate hairs on the throat, collar, and 
behind the ligule. Peduncles solitary, terminal on leafy culms; exserted up to 6 cm. from 
the nearly bladeless uppermost sheath; inflorescence 8-18 cm. long, 7-15 cm. wide, a 
rather dense fan-shaped panicle of 8-33 racemes borne racemosely along a short, angled 
rachis 5-11 cm. long; racemes crowded, ascending or later drooping, 7-16 cm. long, the 
lower ones longer than the upper; base of each raceme bearing a tuft of stiff white 
elongate hairs; rachis flat, 0.8-1.4 mm. wide, with a low midrib; spikelets solitary, the 
raceme 2-rowed. Spikelets 3.7-4.6 mm. long, ovate 2.3-2.7:1, acuminate, strongly dor- 
sally flattened; first glume a minute nerveless scale or commonly absent; second glume 
and lower (sterile) lemma equal, as long as the spikelet; second glume 3-5-nerved, the 
margins bearing a fringe of fine silky hairs; sterile lemma similar, 3-7-nerved, the mar- 
gins very sparsely ciliate; upper (fertile) floret 3.3-4.3 mm. long, ovate 2.4-3.1:1, acumi- 
nate, strongly dorsally flattened, the lemma finely striate; palea similar, flat; lodicules 2, 
truncate; anthers 3, orange, 2.2-2.8 mm. long; styles 2, separate; stigmas deep purple; 
caryopsis elliptical 2:1, brownish, with a dark line two-thirds as long arising from the 
base opposite the embryo. Chromosome number n = 10 from Costa Rican specimens. 

Roadsides, marshes, open weedy sites, pastures, mostly in moist 
areas; sea level to 600 m. elevation, rarely higher; near the Pacific and 
Caribbean Coasts; San Jose area; Turrialba; Laguna de Arenal. 
Blooming July to November. Southern Mexico to Argentina and 
Ecuador. Common name: Gamalote. 

Paspalum humboldtianum Flugge, Monogr. Paspalum 67. 1810. 
Figure 156. 

Rhizomatous perennial, forming tufts; culms 59-120 cm. long, erect to decumbent; 
rhizomes abundant, scaly; culms branching mostly from the lower nodes; internodes 
glabrous, hollow, 1.5-2.0 mm. thick; nodes not prominent, glabrous or appressed- 
bearded; lower leaf sheaths overlapping, the upper shorter than the internodes; foliage 
aggregated on the lower parts of the plants; overlapping margin of the sheaths ciliate, 
the surfaces from nearly glabrous to papillose-hirsute or hispid, especially toward the 
apex; ligule a thin brown membrane, 1.8-3.8 mm. long; leaf blades 7-14 cm. long, 8-17 
mm. wide, flat, more or less appressed-pilose to nearly glabrous; sometimes papillose- 
ciliate with long hairs; base of blade broad, subcordate; tip acuminate; uppermost leaf 
blade much reduced. Inflorescences terminal on leafy culms; peduncle exserted 6-12 cm.; 
panicle 5-11 cm. long, composed of 1-5 ascending racemes borne on a common rachis up 
to 7 cm. long; rachis of individual racemes 4-7.5 cm. long, the rachis 1.0-1.5 mm. wide, 
with a wide white midrib and flattened green margins; tip naked or bearing abortive 
spikelets; spikelets overlapping, in 2 or 4 rows in the same raceme, one of each pair 
longer-pedicellate than the other. Spikelets dorsally flattened, 3.0-3.7 mm. long, ovate 
2.3-2.4:1, acute, prominently white-ciliate; first glume absent; second glume as long as 
the spikelet, 3-nerved, the lateral nerves marginal, thickened, bearing a dense row of 
radiating, pustulose-based white cilia 2-3 mm. long; surface glabrous or sometimes pu- 
berulent; lower (sterile) lemma 3.0-3.5 mm. long, 3-nerved, narrower than the glume, 
ovate 3:1, glabrous or scabrid toward the tip; upper (fertile) lemma 2.3-2.7 mm. long, 
elliptic-obovate 2.3:1, whitish, smooth and shining, firm, not rigid; palea similar and of 




FIG. 156. Paspalum humboldttanum. Inflorescence, two views of a spikelet, fertile 
floret. 



423 



424 FIELDIANA: BOTANY 

equal length; lodicules 2, truncate; anthers 3, purple, 1.5-2.2 mm. long; styles 2, sepa- 
rate; stigmas purple. 

Rare or overlooked; dry tuff savannas, steep dry road embank- 
ments. Liberia, Nuestro Amo, San Rafael de Cartago, San Juan 
Norte, Catarata Los Novios, Boruca savannas. August to November. 
Mexico to Argentina. 

Paspalum humboldtianum was included in the subgenus Ceresia by 
Chase, along with P. pectinatum and P. stellatum in our flora. It 
differs from the other species in its much narrower rachis. Chase 
states that the rachis is 2-3 mm. wide, but our material never has a 
rachis wider than 1.5 mm. 

Paspalum jimenezii Chase, Contr. U.S. Natl. Herb. 28:159. 1929. 
Figure 157. 

Rhizomatous perennial; rhizomes extensive, mostly buried in mud; ascending portions 
of the culms up to 20 cm. long, simple; branching abundant from the rhizomes; inter- 
nodes up to 1 mm. thick, hollow, glabrous; nodes appressed-pilose; leaf sheaths keeled, 
glabrous; overlapping margins of sheaths finely ciliate; ligule a thin membrane, 0.2-0.3 
mm. long; leaf blades flat, mostly 4.5-8 cm. long, 4-6 mm. wide, glabrous, the midrib 
prominent beneath, the tip acute, collar pilose-bearded. Peduncle included in the up- 
permost sheath; inflorescences terminal on leafy culms, 2.5-3.0 cm. long, of 3-8 diverging 
racemes borne on a short common rachis; individual racemes 2.0-2.5 cm. long; rachis 0.5 
mm. wide, flat; pedicels 0.3-0.4 mm. long; spikelets borne in 2 rows. Spikelets 1.4-1.5 
mm. long, ovate 5:3, acute; first glume absent; second glume and lower (sterile) lemma 
equal, as long as the spikelet, glabrous, hyaline, each with 2 marginal nerves, the 
midribs absent; upper (fertile) floret as long as the spikelet, the lemma faintly striate, 
stiff but not rigid; palea equal, flat; anthers 3, pinkish, 0.6 mm. long; styles 2, separate; 
stigmas purple. 

Paspalum jimenezii is a sterile clone, reproducing only by rhizomes. 
It occurs on the muddy banks of the tidal Rio Bebedero, at a locality 
known as Las Playitas, on Hacienda Taboga, southwest of Canas. It 
was first collected at this locality in 1913 by Jimenez, and we found it 
there again in 1969. At that time, it formed a sizable population on the 
banks of the river. Chromosome counts made from cytological fixations 
showed that the chromosome number is 2n = 30, and that meiosis is 
highly irregular. No viable pollen is formed, and both our collections 
and the type specimen show collapsed, empty, and shrunken pollen 
grains. No other specimens of P. jimenezii than the two cited below 
are known. A third specimen from Panama in US, so named by Chase, 
has normal fertile pollen and is probably of different origin. It is prob- 
able that P. jimenezii is the result of a cross between the similar P. 
standleyi (n = 20) and a diploid species, possibly P. orbiculatum. I 
revisited the type locality in 1976, but was unable to find the original 
colony. Extensive pasture improvement had been carried out at the 




FIG. 157. Paspalum jimenezii. A, blooming plant with rhizomatous base; B, raceme 
from rachis side; C, raceme from spikelet side; D, spikelet. 



425 



426 FIELDIANA: BOTANY 

site, and it is possible that the clone had been destroyed. Its long 
persistence at this site probably occurred because the plants were able 
to cope with tidal mud deposition by their extensive production of 
rhizomes. A further account of the cytology is in Pohl & Davidse 
(1971). 

Guanacaste: Las Playitas del Rio Bebedero, Hda. Taboga, 5 January 
1913, 0. Jimenez 742 (holotype in US, duplicate in CR); same location: 
16 January 1969, Pohl & Davidse 11660. Jimenez stated that Las 
Playitas was at an altitude of 50 m. This is certainly an error, as the 
Rio Bebedero is tidal at that point. 

Paspalum lineare Trin. , Gram. Pan. 99. 1826. 

Densely caespitose perennial in small hard clumps; bases of the culms covered with old 
sheaths (basal foliage often burned off); culms slender, seldom branched, 1.0-1.5 mm. 
thick, hollow, glabrous, 40-110 cm. tall; nodes densely upwardly bearded with appressed 
white hairs; leaf sheaths pilose to glabrous, with a few elongate hairs around the throat; 
basal leaf blades up to 60 cm. long, the culm blades much shorter, the uppermost one 
much reduced; ligule a short firm membrane, 0.4-1.0 mm. long, decurrent on the sheath 
margins; auricular hairs long, conspicuous, papillose-based; leaf blades 1.0-1.5 mm. 
wide, laterally flattened, the upper surface reduced to a minute groove by the union of 
the left and right sides of the blade. Peduncle exserted 10-15 cm. , glabrous except for the 
bearded apex; racemes usually 2, 4-6 cm. long, ascending, the lower one sessile, the 
upper one a rachis 4-10 mm. long; a tuft of long, silky hairs at the base of each raceme; 
rachis of the racemes zigzag, 0.4-0.7 mm. wide, the basal 4-6 mm. naked; spikelets few, 
rather distant, solitary in 2 rows; pedicels up to 2 mm. long. Spikelets 4.3-5.0 mm. long, 
narrowly elliptical 2.6-2.9:1, acute; first glume absent; second glume and lower (sterile) 
lemma equal, 5-nerved, firm, glabrous except for 2 tufts of minute hairs on the basal 
margins of the glume; upper (fertile) floret rigid, stramineous, papillose-striate, 3.8-4.3 
mm. long, elliptical 2.7-2.9:1, acute; palea similar, slightly concave; lodicules 2, truncate; 
anthers not seen; styles 2, separate; stigmas purple; caryopsis elliptical 2.0-2.4:1, ca. 2.6 
mm. long, tan, with a red line half its length opposite the embryo. 

Rare, dry savannas. Two old specimens are known from Costa Rica. 
They are: Savanes de Cabagra, March 1892, Tonduz 6548; Savanes de? 
Tigre?, Tonduz 6544- Southern Mexico (Chiapas) and Belize to Argen- 
tina; Cuba. 

Paspalum microstachyum Presl, Rel. Haenk. 1:215. 1830. Figure 
158. 

Duration indefinite, said to be annual; plants caespitose, but the bases of the culms 
sometimes decumbent and rooting; culms 15-85 cm. long, branching from the base and 
lower nodes; prophylla2-6 cm. long; internodes 1-2.5 mm. thick, hollow, glabrous, green 
or purple; nodes glabrous, dark, not prominent; leaf sheaths longer or shorter than the 
internodes, glabrous to papillose-pilose; ligule a thin brown membrane, 0.5 mm. long, 
sometimes with longer hairs behind it; leaf blades flat, ovate 5-10:1, acuminate, 4-23 cm. 
long, 6-23 mm. wide, more or less papillose-pilose on the upper or both surfaces; bases of 
upper and middle blades strongly cordate; lower blades tapering to a narrow base. 




FIG. 158. Paspalum microstachyum. Inflorescence, two views of a spikelet, fertile 
floret. 



427 



428 



FIELDIANA: BOTANY 



Inflorescences mostly terminal, sometimes a smaller secondary one axillary from the 
uppermost sheath; panicle elongated, 8-14 cm. long, slender, of up to 30 solitary, paired, 
or whorled spreading or drooping racemes borne along a slender angled rachis; indi- 
vidual racemes 5-30 mm. long; central rachis and those of the racemes bearing scattered 
elongate weak hairs, to 4 mm. long; pulvini with tufts of hairs; rachis of racemes flat, 
0.6-0.8 mm. wide, bearing paired spikelets in 2 rows on each side of the midrib; pedicels 
slender, the longer one of each pair 1.5-2.0 mm. long, the shorter about a third as long. 
Spikelets 1.4-1.6 mm. long, elliptical-obovate 1.5-1.6:1, finely puberulent, the bracts 
whitish or rusty-spotted, hyaline; first glume absent; second glume slightly shorter than 
the spikelets, 3- or rarely 5-nerved; lower (sterile) lemma as long as the spikelet, 3- 
nerved; upper (fertile) floret elliptic-obovate, whitish, striate, 1.4 mm. long; lemma 
rather strongly convex; palea similar, flat; anthers 3, purple, 0.4 mm. long; caryopsis 
elliptical 1.4:1, opalescent, ca. 1.0 mm. long. Chromosome number n = 10 from Costa 
Rican and Venezuelan specimens. 

Occasional, roadsides, cut-over rain forests, mostly at elevations 
below 100 m.; northern Guanacaste to Puntarenas; Rio La Vieja, 
Puerto Viejo, Hacienda de Zent, Atenas, Matina. Guatemala to Peru 
and Brazil. 

This rather weedy species appears to have no close relatives in our 
flora. 

Paspalum minus Fourn., Mex. PI. 2:6. 1881. Figure 159. 




FIG. 159. Paspalum species. P. mimis (left): inflorescence, two views of a spikelet, 
fertile floret; P. notatum (right): inflorescence, two views of a spikelet, fertile floret. 



BURGER: FLORA COSTARICENSIS 429 

Rhizomatous perennial, forming flat mats; rhizomes thick, woody, scaly; culms un- 
branched, 27-53 cm. long, mostly lying on the ground; internodes 1-2 mm. thick, gla- 
brous, often collapsed in dry specimens and possibly solid; nodes dark, shrunken, 
glabrous; foliage yellowish green; leaf sheaths keeled, the lower ones longer than the 
internodes, the foliage aggregated near the base; upper sheaths shorter than the inter- 
nodes; sheaths glabrous except for papillose-based cilia on the overlapping margin, 
especially near the apex; ligule a thin brownish membrane, 0.2-0.7 mm. long, backed by 
a dense row of stiff erect hairs ca. twice as long; dewlap conspicuous, yellowish; leaf 
blades as wide as the sheath apex, the lower ones 8-14 cm. long, 4-7 mm. wide, the 
midrib conspicuous beneath; blade folded near the base; lower margins and occasionally 
the upper surface bearing scattered elongate pustulose-based hairs up to 8 mm. long; tip 
abrupt. Peduncles included in the uppermost bladeless sheath or exserted up to 3 cm.; 
inflorescences terminal on the culms, solitary, consisting usually of a pair of conjugate 
equal racemes, rarely a third one a short distance below; a pair of stiff deltoid bracts and 
a tuft of silky hairs borne at the apex of the peduncle between the racemes; individual 
racemes 4-7 cm. long; rachis 0.8-1.0 mm. wide, zigzag, usually bearing a solitary spikelet 
at its tip; pedicels ca. 0.5 mm. long. Spikelets solitary in 2 rows, 2.4-2.5 mm. long, 
ovate-obovate, blunt-pointed, glabrous, green; first glume absent; second glume and 
lower (sterile) lemma equal, as long as the spikelet; second glume 3- or rarely 5-nerved; 
sterile lemma usually 3-nerved; nerves marginal; upper (fertile) floret 2.1-2.2 mm. long, 
elliptical or obovate, whitish, striate; lemma more convex than in P. notatum; palea 
similar, flat; anthers 3, purple, 0.9-1.2 mm. long; caryopsis 1.4 mm. long, elliptical 1.4:1, 
tan; styles reflexed along the upper edges of the caryopsis. 

Open, often disturbed areas; savannas, roadsides, pastures; grassy 
sea beaches; sea level to 750 m. elevation, rarely higher. Common in 
Guanacaste, scattered elsewhere; San Jose, Turrialba, General Valley, 
Puntarenas, Golfito, Barro de Colorado, Tortugero. June to January. 
Southern Mexico to Peru and Paraguay; West Indies. 

The plants may be often overlooked because of their mat-forming 
habit. Our single chromosome count from Costa Rica (Pohl 12954) is n 
= 25, an anomaly in a genus with a basic number of x = 10. Previous 
counts for this species indicated n = 10 or 20. Paspalum minus is very 
similar in spikelets and inflorescence to P. notatum, differing in 
spikelet size and growth habit. Paspalum pumilum is also similar, but 
has yet smaller spikelets and lacks the woody rhizomes common to 
both of the above species. 

Paspalum multicaule Poir., in Lam. Encycl. Suppl. 4:309. 1816. 
Figure 149. 

Caespitose annual in small tufts; plants (5) 12^40 cm. tall; culms branching from the 
base or lower nodes; internodes glabrous, ca. 1 mm. thick, hollow, thick-walled; 
prophylla up to 2 cm. long; nodes glabrous; foliage mostly on the lower half of the culms; 
sheaths keeled, nearly glabrous to papillose-hispid, the margins softly ciliate; ligule a 
thin brown membrane, 0.3-0.5 mm. long; leaf blades mostly 4-12 cm. long, 1.5-2.5 mm. 
wide, conspicuously papillose-hispid on both surfaces with hairs up to 5 mm. long; sur- 



430 FIELDIANA: BOTANY 

face finely puberulent between the long hairs; midrib prominent beneath; margins of 
blades becoming revolute; uppermost leaf sheath bladeless. Inflorescences terminal on 
the main culm or on leafy branches; peduncle included or exserted from the bladeless 
sheath up to 5 cm.; inflorescence usually a conjugate pair of spreading racemes, these 1-4 
cm. long; rarely a third raceme is borne just below the pair; a pair of minute bracts occur 
at the apex of the peduncle between the racemes; rachis of racemes silky at the base, 
flattened, with a medial ridge, often zigzag, 0.5-0.7 mm. wide; spikelets in 2 rows; 
pedicels less than 0.5 mm. long. Spikelets yellowish, nearly circular, 1.1-1.5 mm. long, 
strongly plano-convex; first glume absent; second glume and lower (sterile) lemma equal, 
as long as the spikelet; second glume 2- or rarely 3-nerved, hyaline, sparsely to densely 
covered with globular hairs; lower (sterile) lemma 2-nerved, glabrous or with a few 
marginal globular hairs; upper (fertile) floret about as long as the thin outer bracts; 
lemma firm, finely striate, its margins sharply inflexed and forming a conspicuous rim 
around the palea; anthers 3, purple, 0.3 mm. long; styles 2, separate, stigmas emerging 
laterally from the spikelet; apex of the ovary and the mature caryopsis with a purple 
splotch; caryopsis nearly circular, 0.8-1.0 mm. long, strongly plano-convex, whitish. 
Chromosome number n = 10 from Costa Rican and Venezuelan specimens. 

Dry rocky savannas, tuff outcrops; northern Guanacaste; Rincon de 
la Vieja, Hacienda Murcielago, Liberia, Las Animas; Buenos Aires, 
Boruca; Hacienda Argentina; 200-750 m. elevation. October to Feb- 
ruary. Southern Mexico; Honduras; Costa Rica to northern South 
America, Peru, Bolivia, and Brazil; West Indies. 

This is one of a group of small annual species including P. 
clavuliferum, P. pictum, and P. parviftorum. 

Paspalum notatum Fliigge, Monogr. Paspalum 106. 1810. Figure 
159. 

Rhizomatous perennial, the rhizomes thick and woody, the short internodes densely 
clothed with stramineous scales; culms simple, erect, 30-70 cm. tall; internodes 1-2 mm. 
thick, hollow but often collapsed in drying, glabrous; nodes dark, contracted, glabrous; 
foliage mostly near the bases of the culms, the upper portions with much reduced leaf 
blades, the ultimate sheath usually bladeless; sheaths keeled, overlapping, glabrous or 
bearing long, papillose-based cilia on the overlapping margin near the apex; dewlap 
mostly yellowish, conspicuous; ligule a short membrane, 0.2-0.4 mm. long, a row of stiff 
hairs just behind it are ca. twice as long; base of blade as wide as the sheath apex, 
somewhat folded; lower leaf margins bearing papillose-based cilia to 4 mm. long; upper 
surface of blades sometimes with a few elongate papillose hairs; lower blades 6-24 cm. 
long, 6-10 mm. wide. Peduncles included or exserted 1.5-4.5 cm., bearing a tuft of glassy 
hairs at the apex between the racemes; inflorescences terminal, solitary, usually com- 
posed of a nearly conjugate pair of equal, diverging racemes, rarely a third present; 
racemes 3-10 cm. long, naked for a short distance at the base, stiff; rachis flattened, 
zigzag, 0.7-0.9 mm. wide; spikelets solitary, in 2 rows, closely placed; apex of rachis often 
bearing a few reduced abortive spikelets. Spikelets greenish, shiny, 3.5-3.8 mm. long, 
broadly ovate 1.4:1, barely pointed; first glume absent (a few spikelets bearing oblong 
first glumes 2.5-3.0 mm. long on one specimen); second glume and lower (sterile) lemma 
equal, as long as the spikelet, glabrous, 5-nerved, the lateral nerves paired near the 



BURGER: FLORA COSTARICENSIS 431 

margins; upper (fertile) floret 2.8-3.3 mm. long, ovate 1.3-1.4:1, whitish, striate; margins 
of lemma sharply infolded, forming a flat rim around the equal palea; lodicules 2, trun- 
cate; anthers 3, purple, 1.8-2.0 mm. long; styles 2, separate; stigmas purple, laterally 
exserted; style branches finally reflexed along the upper edges of the caryopsis; caryop- 
sis elliptical 4:3, tan, ca. 2 mm. long; an oblong brown mark present at the base opposite 
the embryo. Chromosome number n = 20 from a Costa Rican specimen. 

Open disturbed areas, roadsides, pastures, beaches; sea level to 
1,500 m. elevation; occasional in Guanacaste and the Meseta Central; 
Zarcero, Cartago, Limon. June to October. Eastern Mexico to Argen- 
tina; West Indies; widely cultivated in Florida and in other warm 
climates of the World. 

Despite its apparent toughness, this species is cultivated as a forage 
grass. Common name Jengibrillo. A cultivated type with diploid (n = 
10) chromosome number is known as P. saurae (Par.) Parodi and prob- 
ably does not occur in Costa Rica. 

Paspalum nutans Lam., Tabl. Encycl. 1:175. 1791. Figure 160. 

Duration indefinite, probably perennial; plants decumbent and mat-forming, the culms 
rooting at the nodes, branching freely from the rooted nodes, the erect culms simple or 
branched near the base, 25-55 cm. tall; internodes 1-2 mm. thick, hollow, glabrous; nodes 
glabrous; leaf sheaths usually shorter than the internodes, glabrous except for the 
densely ciliate overlapping margins; basal sheaths appressed-pilose; ligule a thin brown 
membrane, 1.2-2.0 mm. long; leaf blades flat, ovate, acuminate, 9-13 cm. long, 7-14 mm. 
wide, tapering to narrow base; more or less appressed-pilose above and below; midrib 
white, carinate below; margins not ciliate. Peduncles 1-3 from the terminal sheath, 
exserted up to 12 cm., glabrous; raceme solitary, arcuate, 3-5 cm. long, with a few 
elongate hairs at its base; rachis ca. 0.5 mm. wide, its edges incurved; pedicels paired, 
about equal. Spikelets mostly paired, in 2 rows on each side of the midrib of the rachis, 
sometimes one of the pair abortive; spikelets 1.7-2.0 (2.2) mm. long, obovate 1.3-1.5:1, 
blunt, strongly plano-convex; first glume usually absent, or if present, a minute ridge or 
nerveless scale, up to 0.4 mm. long; second glume shorter than the spikelet, 1.6-2.0 mm. 
long, 5-nerved, sometimes with a few short hairs on the margins; lower (sterile) lemma 
as long as the spikelet, 5-nerved, glabrous, occasionally with a hyaline palea to 1.8 mm. 
long; upper (fertile) lemma 1.8-2.0 mm. long, obovate-elliptical 1.3-1.4:1, whitish, 
striate, blunt, strongly convex; palea similar, flat; lodicules 2, truncate; anthers 3, white 
or purple-spotted, 0.7 mm. long; styles 2, separate; caryopsis 1.2-1.4 mm. long, broadly 
elliptical 1.2-1.4:1, opalescent; a brown spot near the base opposite the embryo. Chromo- 
some number n = 20 from Costa Rican and Venezuelan specimens. 

Moist forests, along trails or roadsides; elevations 450-1,200 m.; oc- 
casional; Barbacoas, Rivas, La Hondura, Canas Gordas, Aguas Zar- 
cas. January to October; probably blooming yearlong. Guatemala and 
Belize to northern South America and Brazil; West Indies. 

This species is most closely related to P. decumbens, from which it 
differs in larger spikelet size and in chromosome number. 




FIG. 160. Paspalum nutans. Inflorescence, two views of a spikelet, fertile floret. 

432 



BURGER: FLORA COSTARICENSIS 



433 




FIG. 161. Paspalum orbiculatum. Inflorescence, two views of a spikelet, fertile floret. 

Paspalum orbiculatum Poir., Lam. Encycl. 5:32. 1804. Figure 161. 

Duration indefinite; possibly perennial; plants creeping extensively, the decumbent 
stems branching freely and rooting at the nodes; prophylla 10-15 mm. long; erect flow- 
ering culms 5-13 cm. tall; internodes less than 1 mm. thick, glabrous, hollow, the lumen 
small; nodes glabrous or somewhat bearded; leaf sheaths flattened, mostly overlapping, 
glabrous except for ciliation on the overlapping margin; collar and throat ciliate; ligule a 
minute membrane, 0.1-0.2 mm. long; leaf blades flat, ovate 3-10:1, mostly glabrous, the 
base of the blade usually truncate and contracted into a very short pseudopetiole. 
Peduncles mostly included, the uppermost sheath bearing a rudimentary blade at the 
apex, just below the racemes; inflorescence of 2-4 spreading racemes borne along a 
short, flattened common rachis up to 6 mm. long; individual racemes 8-24 mm. long, the 
rachis flattened, 0.5-0.7 mm. wide; pedicels minute, ca. 0.2 mm. long; spikelets in 2 rows. 
Spikelets orbicular, rather flat, 0.9-1.2 mm. long, 0.8-1.0 mm. wide; first glume absent; 
second glume and lower (sterile) lemma as long as the spikelet, hyaline, each bearing 2 
faint nerves at the margins; midribs not present; bracts usually glabrous, tending to 
disintegrate at maturity; upper (fertile) floret as long as the spikelet; lemma finely 
striate, not very convex, becoming reddish at maturity, its margins flattened over the 
edges of the slightly convex palea, forming a rim; anthers 3, purple, 0.3 mm. long; styles 
2, separate; stigmas purple; caryopsis orbicular, 0.7-0.8 mm. long, rather flat. Chromo- 
some number n = 10 from Costa Rican and Venezuelan specimens. 

Creeping on wet roadsides or in water of ditches, mostly at low 
altitudes near both coasts. July to December. Limon, Santa Rosa, 



434 FIELDIANA: BOTANY 

Puerto Viejo, Siquirres, Osa Peninsula. Two old specimens are known 
from the San Jose area, but the elevation seems anomalous. Southern 
Mexico to Panama, northern South America to Ecuador and Paraguay; 
West Indies. 

Paspalum paniculatum L., Syst. Nat. ed 10, 2:855. 1759. An exten- 
sive synonymy is given by Chase. Figure 162. 

Caespitose perennial in large clumps; plants erect; culms mostly 75-150 cm. tall, 
branching from the lower and middle nodes; prophylla up to 8 cm. long; internodes 
glabrous, 3-6 mm. thick, collapsed in drying; nodes prominent, sparsely to conspicuously 
silky-bearded; leaf sheaths mostly overlapping; overlapping margin finely ciliate; lower 
sheaths usually densely papillose-hispid, the upper more or less hispid to nearly gla- 
brous; ligule a thin brown membrane, 0.5-1.0 mm. long; leaf blades flat, lax, mostly 17-35 
cm. long, 13-24 mm. wide, the terminal one much smaller; base usually broad and 
rounded to the sheath apex; midrib prominent, white, keeled beneath; surfaces more or 
less papillose-pilose, sometimes densely so. Inflorescences terminal on leafy culms; 
peduncle exserted up to 15 cm. , glabrous except near the bearded apex; panicles 6-25 
cm. long, open-cylindrical; central rachis angled and grooved, glabrous; racemes usually 
18-70, racemose along the rachis, some of them verticillate; bases or pulvini bearded 
with tufts of long, silky hairs up to 4 mm. long; racemes spreading, often arcuate, the 
lower ones 4-11 cm. long, the upper ones successively shorter; rachis of individual 
racemes triquetrous, slender, 0.3-0.5 mm. wide, bearing scattered fine elongate hairs on 
the margins. Spikelets paired on each side of the midrib, the terminal one on slender 
pedicel ca. 1 mm. long, the other on a shorter pedicel; spikelets obovate 1.2-1.4:1, blunt, 
1.2-1.5 mm. long, finely puberulent, brown or purple, often with dark splotches; first 
glume absent; second glume and lower (sterile) lemma hyaline, equal, as long as the 
spikelet, 3-nerved; upper (fertile) floret ca. as long as the spikelet, stramineous, finely 
striate; lemma convex, the palea similar, flat; anthers 3, deep purple, 0.5-0.8 mm. long; 
styles 2, separate; stigmas purple; caryopsis circular, ca. 0.8 mm. long, tan. Chromo- 
some number n = 10 from Costa Rican and Venezuelan specimens. 

Common in disturbed areas, mostly at low elevations near both 
coasts, also in the Meseta Central, where it occurs to 1,500 m.; road- 
sides, ditches, flood plains, marshes, often on forest margins or in 
partial shade. Blooming yearlong, probably more abundantly during 
the rainy season. Southern Mexico to Argentina; West Indies; intro- 
duced in tropical climates of the Old World. 

This species is quite weedy. It has no close relatives in the Costa 
Rican flora, but may possibly be confused with P. corypheum. 

Paspalum parviflorum Rohde, in Fliigge, Monogr. Paspalum 98. 
1810. Figure 149. 

Diminutive caespitose annual in small tufts; plants 5-14 cm. tall, erect; culms branch- 
ing from the base and lower nodes; prophylla 7-12 mm. long; internodes glabrous, pur- 
ple, less than 0.5 mm. thick, hollow, thick-walled; leaf sheaths more or less keeled, 
overlapping, papillose-pilose with long hairs; ligule a minute membrane, 0.1-0.2 mm. 
long; leaf blades flat or folded, 1-5 cm. long, mostly less than 1 mm. wide, the midrib 




FIG. 162. Paspalum paniculatum. A, leafy culm; B, inflorescence; C, spikelet pair; D, 
spikelet; E, plant base. 



435 



436 FIELDIANA: BOTANY 

prominent beneath; surfaces and margins bearing elongated papillose-based hairs up to 5 
mm. long. Peduncles mostly included in the uppermost sheath; inflorescence of 1-3 
slender divergent racemes, each 1.0-1.5 cm. long, borne on a short rachis; rachis of 
individual racemes narrow, 0.3-0.4 mm. wide, triquetrous, strongly zigzag, the spikelets 
visible from both sides; spikelets borne in 2 rows, alternating and scarcely overlapping; 
pedicels ca. 0.2 mm. long, ciliate near the apex. Spikelets elliptical-obovate 2-3:1, blunt, 
0.6-0.7 mm. long; first glume absent; second glume and lower (sterile) lemma hyaline, 
weakly 2-nerved near the margins, hyaline and easily disintegrating at maturity; mar- 
gins of lower lemma and second glume bearing minute, peg-like hairs, presenting a 
roughened or pebbly appearance under low magnification; upper (fertile) floret about as 
long as the spikelet, stramineous; anthers 3, 0.3-0.5 mm. long, dark orange; styles 2; 
stigmas purple. 

Paspalum parviflorum was previously known from Panama, Ven- 
ezuela, Surinam, Brazil, French Guiana, and Puerto Rico. The only 
Costa Rican collection is the following: Guanacaste, 2 km. E of CIA on 
road to Las Animas, elevation 200 m., dry tuff outcrop in open 
Byrsonima-Curatella savanna, 4 December 1968, P. & D. 11531. 
Chromosome number n = 10 from the above specimen. This diminu- 
tive species is most closely related to P. multicaule, P. clavuliferum, 
and P. pictum. 

Paspalum pectinatum Nees in Trin., Gram. Icon. l:pl. 117. 1828. 
Figure 163. 

Densely caespitose perennial in hard tufts, the bases of the plants buried below soil 
level and the foliage frequently burned off; culms erect; foliage mostly at the base of the 
plants or on the lower half of the culms; culms unbranched, 30-100 cm. long; internodes 
1.5-2.5 cm. thick, hollow, glabrous; nodes not prominent; basal sheaths disintegrating 
into fibers; lower sheaths glabrous near the base and more or less hirsute toward the 
apex; upper leaves reduced to bladeless sheaths; ligule a brown membrane, 0.5-1.0 mm. 
long, with dense tufts of long hairs, up to 8 mm. long, behind it; leaf blades 11-65 cm. 
long, 3-7 mm. wide, somewhat revolute, the midrib prominent below; surfaces densely 
hirsute or velvety, the hairs 2-4 mm. long. Peduncles slender, exserted 3-15 cm. from 
the uppermost bladeless sheath, the apex silky-bearded; inflorescences solitary, termi- 
nal, 5-7 cm. long, consisting usually of a strict pair of conjugate racemes, sometimes with 
a third raceme a short distance below; rachis flattened, 2.0-2.5 mm. wide, with a mem- 
branaceous border and a prominent midrib; margins ciliolate or somewhat toothed; apex 
of rachis protruding beyond the spikelets as a naked point; pedicels very short, 0.5 mm. 
long or less; spikelets solitary, densely overlapping in 2 rows. Spikelets cordate-ovate 
2.2-2.3:1, strongly dorsally flattened, papery, 4.5-6.7 mm. long; first glume absent; sec- 
ond glume as long as the spikelet, acute, usually 3-nerved, with a wide papery wing; 
lower (sterile) lemma much narrower than the second glume, ovate, acute, flattened, 
3-nerved, the margins bearing a dense row of spreading, pustulose-based hairs up to 2 
mm. long, their tips extending beyond the margins of the second glume; back of the 
lemma with a few pustulose-based hairs; upper (fertile) lemma ovate 3:1, firm but not 
rigid, strongly dorsally flattened, 3.5-4.5 mm. long, minutely ciliolate at the acute tip; 
palea similar and of equal length; lodicules 2, truncate; anthers 3, ca. 2.2 mm. long; styles 
2, divergent; stigmas purple. Chromosome number n = 10 from Nicaraguan and Sal- 
vadorian specimens. 




FIG. 163. Paspalum pectinatum. Inflorescence, two views of a spikelet, fertile floret. 



437 



438 FIELDIANA: BOTANY 

Rare or overlooked; dry savannas near the CIA, from the La Cruz 
area to Liberia, Buenos Aires, Savanas de Tigre, Guacimo, Paso Real, 
Surubres; elevations 200-400 m. April to August. Southern Mexico to 
Honduras, El Salvador, Nicaragua; Costa Rica and Panama to Colom- 
bia and Brazil. 

This species, P. stellatum, and P. humboldtianum are placed by 
Chase in the subgenus Ceresia, characterized by flattened or winged 
rachises and silky or strongly ciliate spikelets. 

Paspalum pictum Ekman, Ark. Bot. 10:17:11, pi. 1, fig. 6. 1911. P. 
maculatum Nash, N. Amer. Fl. 17:186. 1912. 

Caespitose annual, in small tufts; plants 25-60 cm. tall, erect; culms branching from 
the lower nodes; internodes ca. 1 mm. thick, hollow, glabrous; nodes glabrous; sheaths 
longer or shorter than the internodes, keeled, glabrous, with thin hyaline margins; ligule 
a thin brown membrane, 1.0-2.2 mm. long; leaf blades folded, the distinction between 
sheath and blade obscure; lower blades up to 20 cm. long, 1.5-3.0 mm. wide, the upper 
blades much reduced, the uppermost sheath often bladeless; lower margins of blades 
with a few elongate, pustulose-based hairs, up to 5 mm. long. Peduncles glabrous, 
exserted 5-10 cm. or some included in the sheaths; inflorescences terminal on the main 
culm or on leafy branches; racemes 1-3, borne on a short common rachis 0.5-3.0 cm. long; 
racemes diverging, the rachis narrow, flattened, 0.7 mm. wide, arcuate, 3-7 cm. long, 
bearing a few elongate hairs at the base. Spikelets paired, crowded; pedicels glabrous, 
ca. 0.6 mm. long. Spikelets obovate 5:4, blunt, 1.0-1.1 mm. long, strongly plano-convex; 
first glume absent; second glume and lower (sterile) lemma hyaline, both slightly shorter 
and narrower than the upper (fertile) floret, whose edges are exposed; second glume 
with 0-3 nerves; sterile lemma 4-5-nerved, the lateral nerves paired near the margins; 
both glume and sterile lemma purple-splotched near the apex and sometimes on the 
back; fertile lemma strongly plano-convex, the surface conspicuously tuberculate except 
near the apex; palea similar, flat; anthers 0.2-0.3 mm. long, purple; styles 2, separate; 
caryopsis whitish, with a purple splotch at the apex between the 2 separate styles. 

This species is known from Costa Rica only by a single collection, 
Pittier 4474., which is the type of P. maculatum Nash. A fragment of 
this collection is in US. It was collected on the Boruca savannas in 
November 1891. 

Paspalum pilosum Lam., Tabl. Encycl. 1:175. 1791. Figure 164. 

Caespitose perennial; culms 50-130 cm. long, ascending or spreading, branching from 
the base and middle nodes; internodes 1-3 mm. thick, hollow, glabrous to densely pilose; 
nodes densely pilose-bearded to glabrous; leaf sheaths keeled, glabrous or papillose- 
pilose, especially toward the summit; overlapping margin densely and finely ciliate; 
collar sometimes bearded; ligule a thin brown membrane, 0.6-2.5 mm. long, a row or tuft 
of elongate silky white hairs, up to 6 mm. long, behind it; leaf blades linear, up to 25 cm. 
long, 5-10 mm. wide; midrib white, prominently keeled below; surfaces papillose-pilose 
on both sides; margins ciliate. Peduncles 1-3 from the terminal sheath; sometimes one 
additional from the sheath below, exserted 1-25 cm., glabrous or finely pilose, silky- 
bearded at the apex; racemes solitary, slightly arched, 6-16 cm. long; rachis 1.0-1.5 mm. 




FIG. 164. Paspalum pilosum. Inflorescence, spikelet pair, single spikelet, fertile 
floret. 



440 FIELDIANA: BOTANY 

wide, its margins somewhat incurved, bearing scattered long weak hairs; spikelets 
paired on each side of the prominent midrib; terminal spikelet of each pair on a hispid 
pedicel ca. 1 mm. long, the other spikelet on a very short reflexed pedicel. Spikelets 
glabrous, strongly plano-convex, obovate 1.8-1.9:1, 2.6-3.2 mm. long, dimorphic; termi- 
nal spikelet of each pair with a very short, truncate membranaceous first glume or none; 
lower spikelet of each pair usually with a narrow, acuminate, 1-nerved first glume up to 2 
mm. long, rarely lacking a first glume; second glume slightly shorter than the spikelet, 
2.4-3.0 mm. long, 5-nerved; lower (sterile) lemma as long as the spikelet, usually 5- 
nerved, or the midnerve suppressed; apex blunt, forming a rim around the tip of the 
fertile floret; lower lemma enclosing a 2-nerved membranaceous palea nearly as long, 
usually bearing 3 well-developed anthers; upper (fertile) floret ovate, 2.5-2.8 mm. long, 
the lemma strongly convex, conspicuously striate, whitish; palea similar, flat; lodicules 2, 
truncate; anthers 3, deep purple, 1.0-1.2 mm. long; styles 2, separate; stigmas plumose, 
deep purple. Chromosome number n = 40 from Costa Rican and Venezuelan specimens. 

Widespread, mostly on the Pacific slope, at altitudes from 380-1,200 
m.; common in scattered sites, on savannas, roadsides, pastures, and 
disturbed areas; rather weedy. Blooming July to January. Hda. 
Guachipelin to the Meseta Central; General Valley; Cariblanco; 
Moravia de Chirripo. Belize to Panama and northern South America to 
Bolivia and Brazil; Trinidad. 

Paspalum plicatulum Michx., Fl. Bor. Amer. 1:45. 1803. Figure 
165. 

Common and weedy, sea level to 600 m. elevation, rarely up to 1,200 
m.; open disturbed areas, roadsides, savannas, beaches, on both 
Pacific and Caribbean slopes; often forming large colonies. Blooming 
yearlong, but most abundantly from April to September. The various 
members of the P. plicatulum complex range from the southeastern 
United States to Argentina and the West Indies. 

This species is a member of the informal group Plicatula of Chase. 
The species all have deep brown fertile florets. Paspalum convexum, 
P. boscianum, and P. centrale belong to this group. Their taxonomy is 
intricate and is complicated by polyploidy and cytological ir- 
regularities. 

KEY TO VARIETIES OF Paspalum plicatulum 

la. Foliage entirely glabrous var. glabrum 

Ib. Leaf blades and sometimes sheaths bearing pubescence 2 

2a. Sheaths and blades densely long-pilose var. villosissimum 

2b. Sheaths glabrous; upper surfaces of leaf blades hairy near base var. plicatulum 

Paspalum plicatulum var. plicatulum. 

Caespitose perennial; plants 70-150 cm. tall, the culms erect to arching, branching 
sparsely from the lower and middle nodes; internodes compressed, glabrous; nodes 
glabrous; leaf sheaths keeled, mostly overlapping, glabrous or nearly so; ligule a thin 




FIG. 165. Paspalum plicatulum. Inflorescence, two views of a spikelet with wrinkled 
sterile lemma, fertile floret. 



441 



442 FIELDIANA: BOTANY 

brown membrane, 1.0-3.5 mm. long; leaf blades flat, folded near the base, up to 43 cm. 
long, 6-12 mm. wide, the lower surface glabrous, the upper surface sparsely to densely 
long-pilose near the base; uppermost leaf blade very reduced or obsolete. Peduncles 
included in the uppermost sheath or exserted up to 17 cm.; inflorescences terminal on the 
main culm or leafy branches; panicles 6-22 cm. long, composed of 2-14 solitary racemes 
borne along an angled and grooved central rachis; individual racemes with a tuft of long 
hairs at the base; lowermost racemes 3-11 cm. long, the upper ones progressively 
shorter; rachis 0.7-1.1 mm. wide, zigzag; spikelets normally paired and the raceme thus 
4-rowed, sometimes one member of the pair abortive or lacking, and the raceme hence 2- 
or 3-rowed. Spikelets usually 2.4-2.8 mm. long, elliptical-obovate 1.4-1.5:1, strongly 
plano-convex, grayish, or brownish when fully mature; first glume absent; second glume 
5-7-nerved, slightly shorter than the spikelet, usually appressed-pubescent, occasionally 
glabrous; lower (sterile) lemma 5-nerved, glabrous, transversely wrinkled within the 
margin; upper (fertile) floret nearly as long as the spikelet, rigid, longitudinally striate, 
deep chestnut brown, strongly convex; palea similar, flat; lodicules 2, truncate; anthers 
3, deep purple, 1.5-1.7 mm. long; styles 2, separate; stigmas purple. Chromosome 
number of P. plicatulum var. plicatulum is n = 20 from numerous Central American 
collections. 

Paspalum plicatulum var. villosissimum Pilger, Bot. Jahrb. Syst. 
30:131. 1901. 

This variety differs from var. plicatulum in stature, being usually 55-100 cm. tall, and 
in the usually densely pilose sheaths and blades. The leaf blades are narrower, usually 
2-5 mm. wide and densely pilose. Inflorescence 7-12 cm. long, of 2-6 racemes, the lower- 
most 3-7 cm. long, the upper shorter; rachis zigzag, 0.5-0.7 mm. wide. Spikelets 2.2-2.7 
mm. long, obovate 1.4-1.7:1; first glume absent; second glume and lower (sterile) lemma 
equal, as long as the spikelet, 5-nerved; glume appressed-pubescent, the lemma gla- 
brous. 

Dry Curatella-Byrsonima and Crescentia savannas at low eleva- 
tions, northwestern Guanacaste from the La Cruz area to Liberia. 
June to July. Most chromosome counts of this variety have indicated 
that it is diploid, with n = 10; however several of our Costa Rican 
accessions have had n 20, with considerable meiotic irregularity. 

Paspalum plicatulum var. glabrum Arech., Anales. Mus. Nac. 
Montevideo 1:58. 1894. 

No Costa Rican collections of this variety have been identified, but it 
may occur. The plants, like those of var. villosissimum, are generally 
smaller and more slender than those of var. plicatulum. Chromosome 
number n = 10 from a Mexican collection. 

Paspalum pulchellum Kunth, Mem. Mus. Hist. Nat. 2:67. 1815. 
Figure 166. 

Caespitose perennial in small clumps; plants 15-55 cm. tall, erect; culms unbranched, 
slender; internodes less than 1 mm. thick, hollow, thin-walled, glabrous; nodes con- 
tracted, upwardly bearded; bases of the sheaths also bearded; foliage mostly aggregated 






FIG. 166. Paspalum pulchellum. A, plant habit; B, inflorescence; C, portion of a 
raceme; D, spikelet, showing sterile lemma; E, spikelet, showing exposed back of fertile 
lemma. 



443 



444 FIELDIANA: BOTANY 

near the base of the plants, the upper parts of the culms nearly naked, with elongated 
internodes and short or obsolete leaf blades; lower sheaths glabrous or more or less 
appressed-silky; the knotty bases of the plants often densely silky; upper sheaths nearly 
glabrous; ligule a minute membrane, 0.2-0.3 mm. long; leaf blades up to 20 cm. long, 1-2 
mm. wide, usually folded or involute, usually copiously papillose-pubescent with 
spreading hairs up to 4 mm. long. Peduncles included in the uppermost bladeless sheath 
or exserted up to 10 cm.; inflorescences terminal on the culms, solitary, of 2-4 racemosely 
arranged divergent racemes borne along a short flattened rachis ca. 5 mm. long; a tuft of 
silky hairs at the base of each raceme; individual racemes 2-7 cm. long; rachis flat, zigzag, 
up to 1 mm. wide, with 2 green lines flanking the white midrib; a solitary spikelet borne 
on the tip; spikelets solitary, alternating in 2 rows; pedicels up to 0.5 mm. long, ciliate. 
Spikelets 1.7-2.0 mm. long, obovate 1.1-1.6:1, rounded to a narrow tip; first and second 
glumes absent; lower (sterile) lemma as long as the spikelet, usually pinkish to deep 
purple, 3-nerved, the lateral nerves marginal, the edges inflexed over the margins of the 
upper (fertile) floret; fertile lemma strongly convex, shining, as long as the sterile 
lemma; palea similar, flat; lodicules 2, truncate; anthers 3, deep purple, 1.1-1.4 mm. long; 
styles 2, separate; stigmas purple. Chromosome number n = 10 from a Venezuelan 
specimen. 

Occasional, dry Curatella-Byrsonima savannas, from Liberia to- 
ward the Nicaraguan border; elevations 75-200 m. June to July. 
Guatemala, Belize, eastern Honduras and Nicaragua; northern South 
America from Venezuela to French Guiana and Brazil; West Indies. 

The racemes of this species are often striking because of the contrast 
between the purple sterile lemma and the shiny whitish fertile lemma. 
In one population from Liberia, however, plants with purple and yel- 
low spikelets occurred together. 

Paspalum pumilum Nees, Agrost. Bras. 52. 1829. Figure 167. 

Caespitose perennial in dense tufts; plants forming flat mats; culms 10-40 cm. long, 
branching from the base only; prophylls in the basal rosette evident, up to 2.5 cm. long; 
culm internodes 1.0-1.5 mm. thick, hollow, glabrous; nodes glabrous, not prominent; 
foliage mostly clustered near the base, the culm blades few, the uppermost leaf reduced 
or lacking a blade; sheaths and blades softly pubescent; ligule a thin membrane, 0.5-1.0 
mm. long; leaf blades 5-10 cm. long, 3-7 mm. wide, flat, tapering rather abruptly to a 
cuspidate tip. Peduncle included or exserted up to 6 cm.; inflorescence terminal, usually 
of a nearly conjugate pair of racemes, sometimes a third one borne below them; racemes 
divergent, often curved, 2.5-4.0 cm. long, slender, the spikelets solitary, borne in 2 
rows. Spikelets ovate-elliptical, rounded at the tip or barely acute, glabrous, 1.5-1.8 mm. 
long, 1.1-1.2 mm. wide; first glume usually absent, or present on a few spikelets, usually 
a minute deltoid nerveless scale, up to 0.2 mm. long, rarely up to 1.2 mm. long; second 
glume and lower (sterile) lemma equal, as long as the spikelet, 3-nerved, the lateral 
nerves close to the margin; upper (fertile) floret slightly shorter; lemma stramineous, not 
strongly convex; palea flat; lodicules 2, truncate; anthers 3, purple, 0.7 mm. long; styles 
2, separate, naked below; stigmas purple. 

This species is known in Costa Rica only by the following specimen: 
Heredia, 3 km. S of crater of Volcan Barba, full sun in roadway, 
prostrate in circular patches, chromosome number n = 10, P. & D. 



BURGER: FLORA COSTARICENSIS 



445 




FIG. 167. Paspalum pumilum. Inflorescence, two views of a spikelet, fertile floret. 

11777, 24 March 1969. West Indies and northern South America to 
Uruguay and Chile. 

Paspalum reclinatum Chase, J. Wash. Acad. Sci. 33:316-317. 1943. 
Figure 146. 

Duration indefinite; plants sprawling, the culms long-decumbent and rooting from the 
lower nodes, branching freely from the rooted portions; ascending portions 30-45 cm. 
long; prophylla up to 4 cm. long; internodes 1-2 mm. thick, hollow, glabrous; nodes 
glabrous, dark; leaf sheaths mostly shorter than the internodes, glabrous or the margin 
sparsely pilose; ligule a thin brown membrane, puberulent on the back, 0.7-2.0 mm. long; 
leaf blades 5-14 cm. long, 4-9 mm. wide, glabrous or puberulent above the ligule, flat and 
thin. Peduncle included in the uppermost sheath or short-exserted; panicles terminal on 
ascending leafy branches, 5-10 cm. long, open-cylindrical, ca. 4 cm. wide, made up of 6-11 
ascending or drooping racemes, each 1.5-2.5 cm. long; rachis of racemes slender and 
pilose at the base, flattened and foliaceous, 1.0-1.2 mm. wide except at the base, tapering 
to a narrow apex that bears a solitary spikelet at the tip; spikelets borne alternately in 2 
rows on slender, short-puberulent pedicels, the 2 rows slightly wider than the rachis. 
Spikelets 2.2-2.9 mm. long, ovate 2.0-2.3:1; first glume absent; second glume and lower 
(sterile) lemma equal, glabrous, 3-nerved, white or purplish, thin, slightly exceeding the 



446 FIELDIANA: BOTANY 

upper (fertile) floret; fertile floret ovate 2:1, blunt, 2.0-2.5 mm. long, the lemma smooth 
and shining, whitish, firm; palea of equal length and similar appearance, flat or slightly 
concave; anthers 3, purple, 1.5 mm. long; styles 2, separate; caryopsis elliptical 2:1, tan. 
Chromosome counts for all Costa Rican collections indicate n = 30. 

Wet, seepy areas, mostly in moist canyons; elevation 1,500-2,100 m. 
February to June. This species was described from South America, 
and our Costa Rican collections are the first from Central America. 
Alto Paloma, Quebrada Corralillo (Rancho Redondo), Rio Grande de 
Orosi, at the power dam 8 km. S of Tapanti. 

The specimen from Alto Paloma (P. & D. 11710) was originally 
reported as P. prostratum Scribn. & Merr., but differs in pubescence 
and chromosome number from that species. 

Paspalum repens Berg., Acta. Helv. Phys.-Math. 7:129, pi. 7. 1762. 
Figure 146. 

Duration indefinite, probably perennial; culms up to 2 m. long, the lower parts creep- 
ing or floating in water, rooting abundantly from the nodes; internodes up to 1 cm. thick, 
hollow, thin-walled, glabrous; nodes glabrous, not prominent; leaf sheaths mostly over- 
lapping, glabrous to papillose-pilose, often inflated; sheath auricles erect, pointed, 3-12 
mm. long; dewlap and collar purple; ligule a ciliolate membrane, 2.5-3.5 mm. long; leaf 
blades usually 20-40 cm. long, 12-14 mm. wide, softly pilose. Inflorescences terminal on 
leafy branches; peduncles short, exserted 2-4 cm.; panicles densely ovoid, 10-16 cm. 
long, 4-9 cm. wide, the numerous ascending or spreading racemes whorled or solitary, 
dropping from the rachis when mature; longest racemes 4-7 cm. long; rachis of racemes 
flattened, 1.5-1.8 mm. wide, foliaceous, extending beyond the ultimate spikelet as a 
naked acuminate point; spikelets alternating in 2 rows on the lower side of each rachis, 
the 2 rows as wide as the rachis. Spikelets 1.8-2.0 mm. long, ovate 2.3:1, acute; first 
glume absent; second glume and lower (sterile) lemma hyaline, equal, as long as the 
spikelet; second glume with 2 marginal nerves; lower lemma 2-3-nerved; upper (fertile) 
floret shorter than the glume and lemma, ca. 1.8 mm. long, the lemma ca. 1.6 mm. long, 
obovate 2.1:1, firm, not rigid, blunt; lodicules 2, truncate; anthers 3, purple, 0.9-1.2 mm. 
long; styles 2, separate. 

Occasional in swamps and ponds, sea level to 300 m. elevation; 
Taboga, Lagunas de San Bernardo, Marais de Sierpe, Rio Colorado, 15 
km. from Barro de Colorado. October to March. Southern Mexico to 
northern South America, southward to northern Argentina; West In- 
dies. Chase (1910) formerly included P. fluitans (Ell.) Kunth of the 
United States under P. repens. 

Paspalum saccharoides Nees in Trin., Gram. Icon. 1. pi. 107. 1828. 
Figure 168. 

Vigorous perennial; culms elongated, usually sprawling or drooping, hanging over 
embankments or bluffs, the bases hard, with coarse, thick roots; lower portions of culms 
rooting upon contact with the soil; internodes thick-walled, woody, 4-8 mm. thick, gla- 
brous or appressed-pilose; nodes swollen; leaf sheaths overlapping, loose, glabrous, or 
pilose at the base; margins ciliate with delicate silky hairs; ligule a minute membranous 



BURGER: FLORA COSTARICENSIS 



447 



ridge, 0.2-0.3 mm. long, with a tuft of long, silky, erect hairs, up to 10 mm. long just 
behind it; midculm blades 10-40 cm. long, 5-13 mm. wide, rather thick and somewhat 
involute, pilose above and glabrous beneath; basal and uppermost leaf blades much 
reduced. Inflorescences terminal on leafy culms; peduncles exserted up to 16 cm.; panicle 
fan-shaped or pyriform, 12-30 cm. long, the numerous slender flexuous racemes fascicled 
along a slender rachis up to 7 cm. long; axils and pulvini long-silky; racemes 9-25 cm. 
long, densely silky with white hairs; rachis triquetrous, ca. 0.5 mm. wide, the angles 
scabrous; spikelets solitary, in 2 rows on the lower 2 sides of the rachis; pedicels slender, 
ca. 0.5 mm. long. Spikelets ovate 3-4:1, acute, 2.0-3.0 mm. long, with a slightly auricu- 
late base; first glume absent; second glume as long as the spikelet, thin, with 2 marginal 
nerves that are copiously ciliate with white, silky hairs 4-6 mm. long; midnerve rarely 
present; lower (sterile) lemma slightly shorter than the glume, 1.8-2.4 mm. long, gla- 
brous, 2-nerved, thin; upper (fertile) floret 1.6-1.8 mm. long, ovate ca. 3:1, acute, firm, 
not rigid; palea similar to the lemma but slightly longer; anthers 3, yellow, 0.8-0.9 mm. 
long; caryopsis 0.8 mm. long, obovate with a nearly truncate apex bearing the persistent 
style base; embryo large, ca. one-third as long as the tan caryopsis. 

Occasional, moist spots, mostly on the Caribbean slope at elevations 
from sea level to 1,200 m., on bluffs, road embankments, above 
streams; rare in the Meseta Central (Dos Rios) and absent from 
Guanacaste; San Miguel (Alajuela); San Ramon to Naranjo, La Hon- 




FIG. 168. Paspalum saccharoides. Inflorescence, two views of a spikelet, fertile floret. 



448 FIELDIANA: BOTANY 

dura, Cartago, Turrialba, Guapiles, San Vito, Limon. April to August. 
Costa Rica to northern South America and the West Indies. 

This species is striking because of the plumose panicle. The spikelets 
are atypical for the genus Paspalum, being of delicate texture and 
having a rather thin fertile lemma. The spikelets are somewhat similar 
to those of some species of Digitaria, notably D. insularis; however, 
the chromosome number of P. saccharoides is n = 10, from Costa 
Rican specimens. The basic chromosome number of Digitaria is x = 9. 
Paspalum saccharoides has no close relatives in the genus and may 
deserve generic status of its own. 

Paspalum scabrum Scribn., U.S.D.A. Div. Agrost. Bull. 4:36. 
1897. 

Duration indefinite, probably annual; culms to 110 cm. long, sprawling and rooting at 
the lower nodes, branching freely from the decumbent portions; prophylla up to 8 cm. 
long; culm internodes 2-3 mm. thick, hollow, retrorsely scabrous with short, sharp 
points; leaf sheaths longer or slightly shorter than the internodes, strongly scabrous on 
the ridges with minute, retrorse barbs; ligule a thin brown membrane, 2.0-2.5 mm. long; 
leaf blades ovate 4-7:1, flat, 8-12 cm. long, 13-28 mm. wide, finely papillose-pilose on both 
surfaces, the base rounded to a short pseudopetiole; midrib scabrous beneath. Inflores- 
cences terminal on erect leafy branches; peduncle included in the uppermost sheath; 
rachis grooved and angled, stiff-pubescent; panicles 10-20 cm. long, up to 5 cm. wide, 
open-cylindrical, the racemes numerous, mostly whorled, 3-4 cm. long, falling as units 
from the rachis at maturity; rachis of racemes flat, foliaceous, 2.0-2.5 mm. wide, the 
midrib scabrous beneath; margins inflexed around the spikelets; tip extended beyond the 
ultimate spikelet as a naked point 3-4 mm. long; spikelets rather distant, forming a single 
row. Spikelets 1.7-2.0 mm. long, ovate 2:1, blunt, glabrous; first and second glumes 
absent; lower (sterile) lemma and upper (fertile) floret equal, as long as the spikelet; 
sterile lemma membranaceous, 3-nerved; fertile lemma smooth and shining, firm but not 
rigid; palea similar and of equal length; lodicules 2, truncate; anthers 3, yellow to 
purplish, 1.4-1.5 mm. long. Chromosome numbern = 10 from a Costa Rican specimen. 

This species, although striking because of its very scabrous foliage, 
is little known and apparently rare. It is known in Costa Rica from San 
Pedro de San Ramon (Cuesta del Toro), between San Ramon and 
Naranjo, and 10 km. E of San Mateo on the road to Atenas. The latter 
specimen grew in a shaded moist gully at 880 m. elevation. December 
to January. Guatemala and Nicaragua to Venezuela, Colombia, Ecua- 
dor, and Bolivia. Paspalum scabrum is similar to P. candidum in 
spikelet characters, but differs in foliage and in chromosome number. 

Paspalum serpentinum Hochst. in Steud., Syn. PL Glum. 1:22. 
1854. Figure 169. 

Caespitose perennial in small tufts; culms erect, 60-100 cm. tall, unbranched; inter- 
nodes up to 1.5 mm. thick, solid, glabrous; nodes glabrous, shrunken; foliage aggregated 
near the base of the plants, the upper parts of the culms with elongated internodes and 




FIG. 169. Paspalum serpentinum. A, inflorescence; B, growth habit; C, two views of a 
spikelet, with mottled bracts. 



449 



450 FIELDIANA: BOTANY 

nearly bladeless sheaths; lower leaf sheaths and blades densely grayish-pilose with 
papillose-based hairs up to 3 mm. long; lower sheaths longer than the internodes, upper 
ones shorter; ligule a thin membrane, 0.3-0.6 mm. long; lower leaf blades up to 30 cm. 
long, 3-4 mm. wide, flat or involute. Peduncles slender, exserted up to 20 cm.; inflores- 
cences terminal on the simple culms, consisting of a conjugate pair of diverging racemes; 
apex of the peduncle with a tuft of silky hairs; individual racemes 3-7 cm. long, the rachis 
narrow, zigzag, triquetrous, 0.5-0.7 mm. wide; pedicels 0.5-1.0 mm. long; spikelets 
solitary in 2 rows, closely overlapping. Spikelets 2.5-2.8 mm. long, broadly elliptical 
1.1-1.3:1, obtuse; first glume absent; second glume and lower (sterile) lemma equal, as 
long as the spikelet, glabrous, mottled with reddish brown lines that radiate inward from 
the margins of the bracts; lemma and glume 3-nerved, the lateral nerves very close to 
the margins; upper (fertile) lemma strongly dorsally flattened, broadly elliptical, 
whitish, finely striate; margins sharply inflexed, forming a flattened rim around the 
palea; palea convex, but the margins sunken beneath the rim of the lemma; lodicules 2, 
truncate; anthers 3, purple, 1.5 mm. long; styles 2, separate; stigmas purple; caryopsis 
tan, broadly elliptical, 1.9 mm. long, with a red line ca. one-third as long at the base 
opposite the embryo. Chromosome number n = 10 from a Nicaraguan specimen. 

Dry savannas at low elevations. The only known Costa Rican speci- 
men is the following: Guanacaste, 21 km. NW of Liberia, shallow dry 
soil, elevation 75 m., Curatella-Byrsonima savanna, 31 July 1966, 
Pohl & Calderon 10175. Belize, Honduras, Nicaragua, Panama; Trini- 
dad and the Guianas. 

Paspalum setaceum Michx., Fl. Bor. Amer. 1:43. 1803. 

Perennial, in small tufts from short, knotty rhizomes; plants 35-65 cm. tall; culms 
ascending, the internodes hollow, glabrous; nodes glabrous, dark; leaf sheaths shorter or 
longer than the internodes, glabrous except for the finely ciliate overlapping margin; 
dewlap and collar bearded; ligule a thin tan membrane, 0.3-0.5 mm. long, with a tuft of 
white hairs behind it; leaf blades flat, usually 8-19 cm. long, 7-11 mm. wide, the length 
8-18 x the width; surfaces glabrous, the margins prominently pustulose-ciliate with 
hairs up to 4 mm. long. Peduncles terminal and axillary, 1-3 exserted up to 30 cm. from 
the terminal sheath, usually 1 included or exserted from 1 to all of the lower culm 
sheaths; inflorescence of 1 or 2 solitary racemes on a short rachis; individual racemes 4-8 
cm. long, arcuate; rachis 0.7-0.8 mm. wide; spikelets paired, in 2 rows on each side of the 
midrib. Spikelets 1.5-1.7 mm. long, elliptic-obovate 1.2-1.3:1, blunt or very slightly 
pointed, strongly plano-convex; first glume absent; second glume and lower (sterile) 
lemma equal, as long as the spikelet, brown-speckled, sparsely to densely puberulent 
with capitellate hairs; second glume 3-nerved; sterile lemma 2-nerved, the midnerve 
absent; upper (fertile) floret about as long as the spikelet, stramineous; lodicules 2, 
truncate; anthers 3, brown, 0.5-0.7 mm. long; styles 2, separate; stigmas purple; caryop- 
sis subcircular, 1.2 mm. long, tan-striate, opalescent, a brown spot opposite the embryo. 
Chromosome number n = 10 from a Costa Rican specimen. 

Sandy beaches of the Caribbean; Tortugero, Limon Airport, Rio 
Banano, Cahuita; Puntarenas; usually rare. June to December. 

This species belongs to a complex group of grasses which have been 
variously treated as a number of species, or as varieties of a single one. 
The most recent treatment, by D. J. Banks (Sida 2:4:269-284. 1966), 



BURGER: FLORA COSTARICENSIS 451 

places all of these plants in nine varieties under P. setaceum. None of 
these varieties matches our plants very well. They come closest to P. 
propinquum Nash, Bull. New York Bot. Gard. 1:291. 1899. The de- 
scription given above is derived entirely from Costa Rican specimens, 
which form a highly uniform group, quite unlike the temperate zone 
representatives of the group. Several of our specimens have old an- 
thers trapped in the mature fertile floret along with a well-developed 
caryopsis. The plants are apparently largely cleistogamous, which may 
account for the multiplicity of forms in the group. 

Paspalum squamulatum Fourn., Mex. PI. 2:11. 1881. Figure 170. 

Plants perennial, caespitose but the culms decumbent and rooting at the lower nodes, 
branching freely from the rooted nodes; erect branches simple, 20-60 cm. long; prophylla 
prominent, 2.0-4.5 cm. long; internodes glabrous, hollow, 1-2 mm. thick; nodes glabrous, 
dark; leaf sheaths keeled, mostly longer than the internodes, glabrous except the finely 
dilate overlapping margin; collar sometimes bearded; ligule a thin brown lacerate mem- 
brane, 2.5-4.5 mm. long; leaf blades mostly 7-11 cm. long, 8-13 mm. wide, dark green, 
flat, the midrib keeled beneath; base usually rounded; surfaces glabrous or more or less 
pilose, especially the upper. Peduncle slender, solitary, included or exserted up to 14 cm. 
from the terminal sheath. Inflorescence usually 4-8 cm. long, a raceme of usually 4-6 
divergent racemes borne singly or paired along a flattened and channeled rachis; base of 
each raceme with a tuft of long hairs; individual racemes 2-8 cm. long; rachis triquetrous, 
0.5-0.7 mm. wide, zigzag; spikelets paired on each side of the midrib. Spikelets glabrous, 
obovate 1.3-1.5:1, blunt, 1.5-1.8 mm. long, strongly plano-convex; first glume absent (a 
minute rudiment present on one specimen); second glume 1.3-1.7 mm. long, 3- or rarely 
5-nerved, slightly shorter than the fertile lemma, which is exposed at the tip; lower 
(sterile) lemma as long as the spikelet, 3-nerved, lacking a palea; upper (fertile) floret 
1.5-1.7 mm. long, obovate 1.2-1.3:1, 1.5-1.7 mm. long, whitish, striate, strongly convex; 
palea similar, flat; lodicules 2, truncate; anthers 3, brown, 0.8-0.9 mm. long; styles 2, 
separate; stigmas dark; caryopsis elliptic 1.2-1.3:1, strongly convex, whitish, opalescent. 
Chromosome number n = 20 from Costa Rican specimens. 

Moist open or partially shaded sites, volcanoes of the Cordillera 
Central; Meseta Central; Canton de Dota; elevations 1,100-2,000 m. 
Blooming June to February. Mexico to Costa Rica. 

Spikelets and vegetative habit of this species are similar to P. nu- 
tans, but the inflorescence is different. 

Paspalum standleyi Chase, J. Wash. Acad. Sci. 17:146. 1927. 

Rhizomatous perennial, forming mats; culms simple, erect, arising from the rooted 
parts, 10-32 cm. tall; internodes up to 1 mm. thick, hollow, thick-walled, glabrous or the 
lower ones pilose; nodes appressed-pilose; leaf sheaths mostly overlapping, glabrous or 
pilose; nodes appressed-pilose; leaf sheaths mostly overlapping, glabrous or pilose, the 
overlapping margin conspicuously pilose-ciliate; foliage mostly aggregated on the lower 
portions of the culms, the upper blades much reduced or lacking; ligule a minute mem- 
brane, ca. 0.2 mm. long; leaf blades linear, rather blunt-tipped, 2.5-7.0 cm. long, 2.5-5.0 
mm. wide, glabrous or sparsely pubescent; pseudopetiole 1.0-1.5 mm. long, densely 




FIG. 170. Paspalum squamulatum. Inflorescence, two views of a spikelet, fertile 
floret. 



452 



BURGER: FLORA COSTARICENSIS 453 

bearded below. Peduncles exserted 1.5-3.0 cm.; inflorescences terminal on leafy culms, 
of 2-5 divergent racemes borne along a short, flattened rachis up to 10 mm. long; indi- 
vidual racemes 1-3 cm. long; rachis flattened, zigzag, 0.5-0.6 mm. wide, naked or bearing 
abortive spikelets for the basal 1 mm.; spikelets borne in 2 rows. Spikelets 1.4-1.5 mm. 
long, ovate 1.6-1.9:1, acute, strongly flattened, glabrous; first glume absent; second 
glume and lower (sterile) lemma equal, as long as the spikelet, each with 2 marginal 
nerves and lacking midribs; bracts thin; upper (fertile) lemma slightly shorter than the 
outer bracts, elliptical, firm but not rigid, finely striate; palea similar, flat; anthers 3, 
purple, 0.8-0.9 mm. long; pollen normal; caryopses developing. 

Gravelly river banks and sand bars. This species was previously 
known only from the type, collected in Panama. I have recently found 
it in abundance along the Rio Platano in Honduras. Our two Costa 
Rican collections are cited below. Paspalum standleyi is probably 
much more widespread in Costa Rica in suitable habitats. 

Guanacaste, moist shady bank of Rio Corobici, Finca La Pacifica, 
elevation 80 m., 3 December 1968, P. & D. 11516; Puntarenas, bank of 
Rio Grande de Terraba, 11 km. SE of Rio Catarata, elevation 100 m., 
12 December 1968, P. & D. 11607. 

Paspalum standleyi was placed by Chase in the group Parviflora, 
consisting mostly of small annuals of dry savannas, whose chromosome 
numbers, as far as known, are all n = 10. Our two collections of P. 
standleyi are both n = 20, and the plants are rhizomatous perennials. 
In inflorescence structure and spikelets, they are very similar to P. 
jimenezii, a rare sterile triploid (2n = 30). It seems most probable that 
these two are closely related, and that P. standleyi is a parent of P. 
jimenezii. 

Paspalum stellatum Humb. & Bonpl. in Fltigge, Monogr. Pas- 
palum 62. 1810. Figure 171. 

Caespitose perennial in dense tufts; culms 55-85 cm. long, erect, most of the foliage 
near the base; upper leaf blades much reduced; internodes few, elongated, less than 1.5 
mm. thick, hollow, glabrous or the upper internodes and peduncle with a few appressed 
hairs; leaf sheaths nearly glabrous at the base, more or less pilose toward the apex, 
shorter than the internodes; ligule a short membrane, 0.2-0.3 mm. long, with a dense 
row of white hairs behind it; leaf blades up to 25 cm. long, 2-4 mm. wide, mostly involute; 
lower surface sparsely hirsute, the upper surface densely hirsute with hairs up to 5 mm. 
long. Peduncles slender, appressed-pilose, silky at the apex; inflorescences solitary, 
terminal on the unbranched culms, 3.5-10 cm. long, composed of a single arched raceme 
or rarely of 2 conjugate racemes; rachis broadly winged, 5-8 mm. wide, infolded about 
the spikelets; midrib flanked by narrow conspicuous green stripes and purplish line on 
each side; margins of rachis wide, thin and papery, russet or chestnut-colored; spikelets 
densely crowded in 2 rows on the lower side of the rachis, but scarcely visible because of 
the dense silky hairs of the bracts; pedicels very short, with a circle of diverging white 
hairs at the tip. Spikelets angular-obovate ca. 2:1, strongly flattened, 3.0-3.2 mm. long; 
callus densely bearded with erect silky hairs ca. half the length of the spikelet; first 






FIG. 171. Paspalum stellatum. A, inflorescence; B, plant base; C, rachis of raceme; D, 
spikelets and pedicels on the rachis; E, spikelet. 



454 



BURGER: FLORA COSTARICENSIS 455 

glume absent; second glume as long as the spikelet, flat, membranaceous, lacking a 
midrib, the 2 nerves marginal, thickened and corky on the upper half, densely ciliate 
with spreading white hairs, those near the base shorter, those on the upper margins 
pustulose-based, 3 mm. or more long; lower (sterile) lemma similar but narrower, mar- 
ginally 2-nerved, 2.5-2.9 mm. long; upper (fertile) floret obovate 2.3:1, minutely stipi- 
tate; lemma firm but not rigid, whitish; palea similar, of equal length; lodicules 2, trun- 
cate; anthers 3, orange, 1.7-2.0 mm. long; styles 2, separate; stigmas brown; caryopsis 
ca. 1.2 mm. long, obovate 1.6:1, tan. 

Rare; Boruca savannas; elevation ca. 450 m. September to De- 
cember. Southern Mexico to northern South America, southward to 
Argentina; Hispaniola. 

Paspalum tonduzii Mez, Fedde. Kept. Sp. Nov. 15:72. 1917. 

Caespitose perennial; height unknown; culms erect or geniculate, unbranched; nodes 
bearded; leaf sheaths longer than the internodes, keeled, papillose-pilose; ligule a very 
short membrane; leaf blades flat, up to 30 cm. long and 10 mm. wide, papillose-pilose 
above and below; midrib broad, whitish. Inflorescence solitary, terminal; peduncle in- 
cluded; panicle 9-11 cm. long, of 7-8 ascending racemes; racemes 3-5 cm. long; rachis 
deep purple, ca. 0.7 mm. wide; spikelets mostly paired, some of the lower ones abortive. 
Spikelets 2.0-2.1 mm. long, obovate 1.7-1.9:1; bracts thin and delicate, mottled purple 
and golden; first glume absent; second glume slightly shorter than the spikelet, 3- 
nerved, occasionally finely puberulent near the apex; lower (sterile) lemma as long as the 
spikelet, 3-nerved; upper (fertile) lemma stramineous, finely striate. 

This species is known only from the type specimen, cited below. The 
description was compiled from a type fragment and photograph in US 
and from descriptions by Mez and Chase. HOLOTYPE: San Jose, 
Plantations de maiz de Santa Maria de Copey, 1,800 m., February 
1908, Tonduz 11767. 

Paspalum turriforme Pohl, sp. nov. Figure 172. 

Gramen altum, perenne, grex Virgata pertinens, a P. densum Poir. spiculis 
acutioribus, longioribus (2.2-2.5 mm. vs. 1.7-1.9 mm.), angustioribus (1.4-1.5:1 vs. 1.0- 
1.2:1), panicula longiore, racemis numerosis (ad 150) recedit, et a P. plenum Chase 
spiculis glabris brevioribus (2.2-2.5 mm. vs. 2.5-3.0 mm.), latioribus (1.2-1.5 vs. 1.7- 
2.3:1) abhorret. 

Tall, vigorous caespitose perennial in dense clumps; plants up to 3 m. tall, erect; culms 
unbranched; culm internodes up to 8 mm. thick, hollow, glabrous; nodes glabrous or 
appressed-pilose; basal leaves numerous, the sheaths strongly keeled, glabrous to 
sparsely hispid, closely distichously overlapping; culm sheaths keeled, overlapping, 
glabrous except the papillose-ciliate overlapping margin; dewlap and collar densely 
long-bearded with papillose-hispid hairs; ligule a firm tan lacerate membrane, 2-5 mm. 
long; a dense tuft of stiff elongate hairs on the upper blade surface just behind the ligule; 
leaf blades 40-95 cm. long, the base narrow, strongly keeled and channeled; blades 
widest at the middle, flat, 12-17 mm. wide; margins strongly scabrous, cutting; tip 
attenuate. Peduncles solitary, terminal, exserted up to 13 cm.; panicle dense, purple, 
narrow, spirelike, 30-50 cm. long, of 40-150 closely placed ascending or drooping 
racemes; common rachis strongly angled and grooved, scabrous; rachis of individual 




FIG. 172. Paspalum turriforme. A, panicle; B, culm base, showing distichous leaf 
sheaths; C, leaf sheath and blade; D, portion of a raceme; E, two views of a spikelet. 



456 



BURGER: FLORA COSTARICENSIS 457 

racemes purple, 1.2-1.5 mm. wide, lower racemes 7-11 cm. long, the midrib prominent 
on the naked side; base with a tuft of long, glassy hairs; margins with scattered long 
hairs to 6 mm. long; spikelets very densely arranged in 4 rows, the total width of the 
spikelets ca. twice the rachis width. Spikelets purple, 2.2-2.5 mm. long, obovate 1.4- 
1.5:1, blunt; first glume absent; second glume and lower (sterile) lemma equal, as long as 
the spikelet, 3-nerved, rather loose and somewhat wrinkled; upper (fertile) floret ca. as 
long as the spikelet; lemma stramineous, rigid, striate, strongly dorsally flattened; palea 
similar, flat; lodicules 2, truncate; anthers 3, purple, 1.5-1.6 mm. long; styles 2, separate; 
stigmas deep purple. 

HOLOTYPE: Costa Rica: Prov. Cartago, 0.5 km. E of Planta 
Radiografica, along railroad, 2 km. W of Paraiso, elevation 1,300 m., 
open grass marsh, 6 February 1969, Pohl & Davidse 11699, ISC. 
ISOTYPES: F, CR, US, K. TOPOTYPE: same location, 28 February 
1969, P. & D. 11742. We collected this species in a marsh at the Planta 
Radiografica near Paraiso. Previous collections were reported by 
Chase from Nuestro Amo and Aguacaliente. February to May. 
Guatemala, Honduras, Costa Rica. 

This is the most striking of the Central American species of Pas- 
palum because of its large size and very conspicuous inflorescences. 
The leaf margins are extremely scabrous and readily cut human skin. 
Our specimens are very consistent in appearance. The strongly keeled 
and overlapping basal sheaths are very distinctive, but may not be 
present on herbarium specimens. Chromosome number n = 20 from 
Costa Rican and Honduran collections. (Originally reported as P. 
plenum.) All meioses were very irregular, with univalents and multi- 
valents present. It is very possible that this species, like many other in 
Paspalum, is apomictic. Paspalum turriforme belongs to the informal 
group Virgata of Chase. 

Paspalum vaginatum Swartz, Prodr. Veg. Ind. Occ. 21. 1788. Fig- 
ure 154. 

Extensively rhizomatous and stoloniferous perennial; erect culm branches 2-50 cm. 
long; prostrate parts of the plants freely branching; erect culms simple or sometimes 
branching from the lower nodes and forming dense tufts; internodes 1-3 mm. thick, 
hollow, glabrous; lower internodes short, the upper ones successively longer; nodes 
glabrous, sometimes swollen, mostly concealed by the overlapping sheaths; leaves usu- 
ally numerous; leaf sheaths loose, keeled, glabrous except for long silky hairs, up to 4 
mm. long, on the short auricles; ligule a thin brown truncate membrane, 0.6-1.0 mm. 
long, adnate to the short sheath auricles; leaf blades 2-14 cm. long, mostly 1-4 mm. wide, 
conspicuously distichous, stiff, straight, ascending or spreading, involute, ridged and 
scabrid above, glabrous except for a few long marginal cilia. Peduncle exserted up to 4 
cm.; inflorescences terminal on erect portions of the culms, 2-8 cm. long, usually com- 
posed of 2 conjugate diverging racemes, sometimes with 1-several more a short distance 
below; terminal racemes equal, naked at the base for up to 1 cm.; each raceme 2-8 cm. 
long, the spikelets borne in 2 rows, overlapping; rachis 1.0-1.5 mm. wide, flat, with a 



458 



FIELDIANA: BOTANY 



prominent midrib, bearing a solitary spikelet on the tip. Spikelets 3.2-3.6 mm. long, 
obovate 2.2-2.6:1, acute, glabrous; strongly dorsally flattened; first glume absent in our 
material; second glume and lower (sterile) lemma equal, as long as the spikelet, mostly 
5-nerved, or sometimes with the midnerve absent; lateral nerves paired, near the mar- 
gins; sterile lemma lacking a palea; upper (fertile) lemma 2.5-3.2 mm. long, obovate, 
acute, whitish, finely striate; palea similar, flat; lodicules 2, truncate; anthers 3, purple, 
1.8-2.0 mm. long; styles 2, separate; stigmas dark; caryopses not seen; most spikelets 
appear sterile. 

Sandy or coral beaches of the ocean, salt marshes along the coast. 
Moin, Limon, Uvita, Rio Banano, Cahuita, Playas del Coco, Coronado 
(Pte). June to December; probably blooming yearlong. North Carolina 
and southward; Baja California and southward on the Pacific Coast; 
southward to Peru and Argentina; West Indies; worldwide in warm 
coastal climates. 

This species and P. distichum are rather similar and have often been 
confused. Chase gives an extensive synonomy. Recent discussions of 
the nomenclature of these species are reviewed under P. distichum. In 
addition to the spikelet and inflorescence differences given in the key, 
P. vaginatum often differs from P. distichum in its tendency to bear a 
large number of closely overlapping leaves, and in the production of 
dense tufts of culms. Our chromosome counts of Costa Rican P. dis- 
tichum indicate n = 30. Literature accounts of the chromosome 
number of P. vaginatum list n = 20. 

Paspalum virgatum L., Syst. Nat. ed. 10, 2:855. 1759. Figure 173. 




FIG. 173. Paspalum virgatum. Inflorescence, two views of a spikelet, fertile floret. 



BURGER: FLORA COSTARICENSIS 459 

Tall, vigorous caespitose perennial; plants 80-250 cm. tall, erect; culms unbranched; 
internodes 3-8 mm. thick, hollow, glabrous; nodes shrunken, dark, glabrous; leaf sheaths 
somewhat keeled, overlapping, glabrous, or the overlapping margin, collar, and dewlap 
papillose-pilose; lower sheaths somewhat spongy, tessellate in drying; ligule a thin 
brown membrane, 1-3 mm. long, with a tuft of long white hairs behind it; leaf blades 
narrow-based, widest at the middle, flat; midrib wide, white, keeled beneath near the 
base; surfaces glabrous or rarely puberulent. Peduncles solitary, terminal, included or 
exserted up to 13 cm.; inflorescences 12-20 cm. long, of usually 8-13 ascending to droop- 
ing racemes; individual racemes 6-18 cm. long, the rachis 1.0-1.5 mm. wide, bearing a 
tuft of white hairs at its base; margins strongly scabrous and with scattered white hairs. 
Spikelets paired, 2.6-3.2 mm. long, blunt, obovate 1.2-1.6:1, mucronate, strongly dor- 
sally flattened; first glume absent; second glume and lower (sterile) lemma equal, as long 
as the spikelet, 5-nerved, puberulent, the hairs longest at the summit; bracts purplish or 
reddish brown; upper (fertile) lemma nearly as long as the spikelet, light reddish brown 
or chestnut colored at maturity, striate; palea similar to the lemma, concave; lodicules 2, 
truncate; anthers 3, purple, 1.3-1.7 mm. long; styles 2, separate; stigmas purple; caryop- 
sis 2.0-2.4 mm. long, broadly elliptical, reddish tan, opalescent. Chromosome number 
n = 20 from Costa Rican and Venezuelan specimens. 

Moist pastures and roadsides, stream banks; occasional in 
Guanacaste and the General Valley, San Vito, Rincon, San Jose area, 
Rio Sixaola near Bambu. Elevations mostly from sea level to 500 m. 
Blooming yearlong, but apparently most frequently during the rainy 
season. Southern Texas to Brazil; West Indies. 

The length of the spikelets in our specimens is in the upper end of 
the range of sizes indicated by Chase, and some exceed it. The plants 
are striking by their large size and vigor. The only closely related 
species in our flora is P. turriforme, which does not have brown fertile 
florets. 

PENNISETUM L. Richard 

REFERENCE: Agnes Chase, The North American species of Pen- 
nisetum, Contr. U.S. Natl. Herb. 22:4:209-234 + X. 1921. 

Perennial or annual caespitose, rhizomatous, or stoloniferous grasses; inflorescence a 
spike of bristly fascicles (much reduced in P. clandestinum), these deciduous from the 
rachis with the contained spikelets; spikelets 1-several per fascicle, usually sessile within 
it, remaining attached and falling with the bristles; bristles (sterile branchlets) usually 
numerous and conspicuous, antrorsely scabrous, often ciliate, mostly concealing the 
spikelets. Spikelets dorsally compressed; first glume much shorter than the spikelet, 
often obsolete, usually 1-nerved or nerveless; second glume usually shorter than the 
spikelet, several-nerved; lower floret sometimes sterile and lacking a palea, or with a 
well-developed palea and a staminate flower, the lemma usually 5-7-nerved; upper floret 
perfect-flowered, the lemma 3-5-nerved; palea well developed; lodicules present or ab- 
sent; anthers 3; ovary with a single style and 2 stigmas, or the styles separate. 

Pennisetum clandestinum is exceptional in its reduced inflores- 
cence, abortive glumes, numerous nerves of the lemmas, and growth 



460 FIELDIANA: BOTANY 

habit. It may merit being placed in a separate genus. Pennisetum is 
closely related to Cenchrus, differing in the separate bristles of the 
fascicle, which are antrorsely scabrous. In Cenchrus, the bristles are 
more or less united into flat spines which are in almost all species 
retrorsely barbed. The basic chromosome number in most species of 
Cenchrus is x = 17, but various numbers excepting x = 17 have been 
found in species of Pennisetum. Although it is difficult to assign a few 
species of this complex definitely to one or the other of these genera, 
the generic characters hold for the great bulk of the species. 
(Panicoideae: Paniceae.) 

KEY TO SPECIES OF Pennisetum 

la. Low creeping plants; inflorescences reduced to 1-several spikelets, concealed within 
sheaths, only their tips protruding, stigmas and stamens exserted; lemmas with 
10-13 nerves P. clandestinum 

Ib. Erect plants with exserted terminal inflorescences composed of numerous bristly 
fascicles on elongated straight rachis; lemmas with 3-7 nerves 2 

2a. Spikelet 1 per fascicle 3 

2b. Spikelets several per fascicle 7 

3a. Inflorescences solitary at tips of main culm or long leafy branches 4 

3b. Inflorescences terminal and axillary, usually numerous on one culm and forming a 

compound inflorescence 6 

4a. Bristles of fascicle scabrous, not ciliate 5 

4b. Bristles of fascicle densely silky-ciliate near their bases, adjacent bristles be- 
coming matted together by hairs P. setosum 

5a. Lower lemma empty, lacking palea or staminate flower; spikelets acuminate or 
caudate; anthers purple, 1.2-1.5 mm. long; styles 2, separate ... P. tempisqiiense 

5b. Lower lemma with palea of equal length and staminate flower; spikelets acute; 
anthers orange, 3.0-3.6 mm. long; style single, bearing 2 stigmas P. complanatum 
6a. Most bristles shorter than spikelet; lower floret sterile and lacking palea 

P. distachyum 

6b. Most bristles longer than spikelet; lower floret with well-developed palea and 
usually a staminate flower P. bambusiforme 

7a. Tall stout plants, culms up to 8 m. tall, 1.0-2.5 cm. thick; spikelets stalked within 
fascicle P. purpureum 

7b. Slender plants, culms less than 1.5 m. tall, 1-2 mm. thick; spikelets sessile in fasci- 
cle 7 

8a. Each fascicle with a single elongate inner bristle, 2-3 x as long as others; 

spikelets 6-9 mm. long P. vulcanicum 

8b. Inner bristle less than twice as long as others; spikelets 2-6 mm. long P. ciliare 

Pennisetum bambusiforme (Fourn.) Hemsl. ex Jacks., Ind. Kew 
2:458. 1895. Gymnothrix bambusiformis Fourn., Mex. PI. 2:48. 1881. 
Figure 174. 

Tall vigorous perennial; the culms arising in clumps from decumbent and sometimes 
rooting bases, up to 1 cm. thick, hollow, glabrous; sheaths shorter than the internodes, 







FIG. 174. Pennisetum species. P. bambusiforme: A, fascicle; P. complanatum: B, 
fascicle; P. distachyum: C, fascicles; P. purpureum: D, fascicle; P. setosum: E, fascicle; 
F, ciliate bristles; P. vulcanicum: G, fascicle. 



461 



462 FIELDIANA: BOTANY 

glabrous or sometimes appressed-bearded just above the nodes and hirsute near the 
apex, papillose-ciliate on the upper margins and auricles; ligule 1-4 mm. long, a short 
membrane ciliate with a dense row of stiff erect hairs; larger leaf blades 20-32 cm. long, 
20-40 mm. wide, more or less hirsute on both surfaces, flat, tapering to a petiole-like 
base. Inflorescence large and compound, of numerous spikes exserted on peduncles of 
varying lengths from the upper leaf sheaths, usually several from one axil, their sub- 
tending leaf blades usually much reduced or obsolete. Individual spikes drooping, usu- 
ally purplish, cylindrical, loose, bristly, 6-10 cm. long, 1-2 cm. thick, including the bris- 
tles; individual fascicles borne on minute scabrous stipes; bristles numerous, scabrid, 
unequal, mostly 6-12 mm. long, surrounding a single spikelet; the uppermost bristle 
directly subtending the spikelet usually 16-18 mm. long, much longer than the others. 
Rachis of the spikes flexuous, angular, scabrous. Spikelets ovate, acuminate, 3.9-5.2 
mm. long, sessile in the fascicle and falling with it; first glume minute, obtuse, 1-nerved; 
second glume broadly ovate, caudate, 1-nerved, 1-2 mm. long; lower lemma longer than 
the upper, 4.0-5.2 mm. long, ovate, caudate, faintly 5-6-nerved, scabrid, enclosing a 
2-nerved palea ca. two-thirds as long; 3 stamens usually present; upper floret perfect- 
flowered, the lemma ovate, caudate, 3.0-4.2 mm. long, faintly 3-5-nerved, chartaceous, 
scabrid, the palea shorter; lodicules 2, truncate; style branches 2, naked below; stigmas 
brown; anthers 3, 1.5-2.0 mm. long. Chromosome number n = 18 from a Costa Rican 
specimen. 

Meseta Central and Cordillera de Talamanca; elevations from 950 to 
2,600 m. This species is a conspicuous part of the vegetation of steep 
slopes, where it arches over other plants, the large purplish compound 
inflorescences drooping. Blooming July to March, possibly yearlong. 
Southern Mexico to northern South America. 

Pennisetum ciliare (L.) Link, Hort. Berol. 1:213. 1827. Cenchrus 
ciliaris L., Mant. 302. 1771. Pennisetum cenchroides L. Rich, ex 
Pers., Syn. PL 72. 1805. 

Perennial from hard, knotty crowns, sometimes with short rhizomes; culms 25-100 cm. 
long, erect, 1-2 mm. thick, solid or hollow, sometimes much branched from basal, lower, 
and middle nodes and becoming bushy; leaf sheaths about equal to the internodes, 
glabrous or sparsely pilose, keeled; ligule a densely ciliate membrane, 0.5-2.5 mm. long; 
blades 3-24 cm. long, 2-9 mm. wide, scabrous, sometimes slightly pilose, tapering to a 
caudate apex. Peduncle exserted; inflorescences terminal on leafy branches; inflores- 
cence a densely cylindrical spike of bristly fascicles, 2-12 cm. long, 1-2.5 cm. wide; rachis 
internodes 0.8-1.0 (2.0) mm. long; fascicles concealing the rachis, often purplish, 6-15 
mm. long, including the bristles, 1.5-3.5 mm. wide; stipe of fascicles pilose, 0.5-1.5 mm. 
long; bristles erect to spreading, flexuous, 4-10 mm. long, 0.2-0.6 mm. wide, conspicu- 
ously ciliate, antrorsely scabrous, very slightly united at the base. Spikelets 2-4 per 
fascicle, 2.0-6.0 mm. long, dorsally compressed; first glume 1.0-3.0 mm. long, 1-nerved, 
thin and membranaceous; second glume 1.3-3.4 mm. long, 1-3-nerved; lower lemma 
2.5-5.0 mm. long, 5-6-nerved, the palea 2.5-5.0 mm. long, enclosing a staminate flower; 
upper lemma 2.2-5.4 mm. long, thin, 5-nerved. 

This species has been cultivated in the grass garden of the IICA at 
Turrialba, but has not as yet appeared in cultivation elsewhere in 
Costa Rica. It has considerable forage potential and is much cultivated 



BURGER: FLORA COSTARICENSIS 463 

in warm climates. This species lies close to the indeterminate boundary 
line between Pennisetum and Cenchrus. Because of the hard-based 
perennial growth habit, lack of flattened, retrorsely-barbed spines, the 
basic chromosome number of a: = 9, and the extensive occurrence of 
apomixis, it seems more closely allied to Pennisetum than to Cen- 
chrus. Native from Africa to India. Common name: Zacate buffel, 
"Buffel grass." 

Pennisetum clandestinum Hochst. ex Chiov. in Annuario Reale 
1st. Bot. Roma 8:41, t. v., fig. 2. 1903. Figure 175. 

Vigorous low creeping perennial; erect branches up to 45 cm. when not grazed, usually 
15 cm. or less tall; rhizomes and stolons present; internodes very short and densely 
clothed with overlapping sheaths; branching profuse, erect branches being produced at 
most nodes; prophylla prominent, retrorsely scabrous on the keels; sheaths keeled, 
glabrous or usually papillose-hirsute, especially on the upper margins; ligule a dense 
ciliate rim, up to 2 mm. long; blades folded or flat, 3-9 cm. long, 2-5 mm. wide, the tip 
blunt and sometimes slightly bifid; upper and lower surfaces glabrous or with scattered 
long hairs. Inflorescence a short mostly concealed axillary spike, the 1-4 spikelets sessile 
and solitary at the nodes of a short flattened rachis, only their tips exserted from the leaf 
sheaths. Spikelets not disarticulating from the plant, each surrounded by a basal fascicle 
of slender bristles of varying lengths, mostly less than half the length of the spikelet; 
shape of spikelet narrowly lanceolate, tapering to a slender apex; first glume absent, the 
second absent or reduced to a minute nerveless scale; lower and upper lemmas equal, 
similar, 19-22 mm. long; lower lemma empty and without a palea, 10-13-nerved; upper 
lemma 10-12-nerved, its palea 2-7-nerved, 16-17 mm. long; lodicules none; flower usually 
hermaphrodite, protogynous, the short-plumose solitary style up to 3 cm. long, exserted 
through the tip of the floret, stigmatic on its exposed parts; anthers 4-7 mm. long, at 
anthesis exserted from the floret on stiff, erect, white filaments up to 3 cm. long, the 
anthers dangling at their tips. Caryopses not seen. 

This is one of the most abundant and widely distributed forage 
grasses in upland pastures, from 1,500 to 2,500 m. elevation. It is 
readily recognized by its creeping stems and light green color. Under 
certain circumstances it becomes an invading weed on cultivated 
ground. It is native to tropical Africa, but is cultivated in many parts of 
the world. In the Americas, it occurs in California, Guatemala, Costa 
Rica, and various South American countries. 

Most reproduction in this species appears to be by the stolons, but 
production of seed, which may be dispersed in the manure of grazing 
animals, has been reported from South America. The erect stamens, 
unique in this species, are often exserted during the mornings in very 
humid weather. Unlike most other grasses, there is but a single 
stigma. Both stamens and stigma are exserted from the tip of the 
fertile floret, because of the lack of lodicules. Many florets with ex- 
serted stigmas show anthers still concealed within the floret, and it is 




FIG. 175. Pennisetum clandestinum. A, growth habit; B, fascicle with a spikelet; C, 
emergent stamens. 



464 



BURGER: FLORA COSTARICENSIS 465 

possible that they do not emerge. Common names are Kikuyo, Pasto 
Kikuyo, Pasto africano. 

Pennisetum complanatum (Nees) Hemsl. , Biol. Centr. Amer. Bot. 
3:507. 1885. Gymnothrix complanata Nees, Bonplandia 3:83. 1855. G. 
mexicana Fourn., Mex. PI. 2:48. 1881. G. grisebachiana Fourn., Mex. 
PI. 2:48. 1881. Figure 174. 

Perennial, rhizomatous, 75-200 cm. tall, or much shorter when grazed; culms branched 
from the lower and middle nodes, often decumbent and rooting, 2-3 mm. thick, glabrous, 
hollow, thick- walled; nodes glabrous or slightly appressed-hispid; sheaths longer than 
the internodes, loose, somewhat compressed, glabrous or ciliate on the upper margins; 
ligule 1.0-1.6 mm. long, a minute membrane crowned with a dense row of stiff white 
hairs; blades 15-55 cm. long, flat or folded, 3-7 mm. wide, attenuate, scabrous, the upper 
surface hirsute near the base. Peduncles exserted; inflorescence a dense cylindrical spike 
of bristly fascicles, terminal on the main culm or on leafy branches, 8-17 cm. long, 7-10 
mm. thick without the bristles, 10-25 mm. including them, tawny or purplish; spikelets 
borne singly in the sessile fascicles on the angled scabrous rachis. Bristles of the fascicle 
numerous, stiff, scabrous; outer bristles 1-5 mm. long, the inner 8-12, one single inner 
bristle much longer, 10-19 mm. long; fascicle deciduous with the solitary contained 
spikelet. Spikelets narrowly ovate, acute, dorsally compressed, 5-6 mm. long; first 
glume rotund or ovate, nerveless or with a single weak nerve; second glume shorter than 
the spikelet, 3.8-4.6 mm. long, 5-nerved, ovate, acute; lower lemma 4.4-5.7 mm. long, 
ovate, 5-nerved, its palea equal; anthers 3, orange, 2.4-3.2 mm. long; upper floret 4.5-5.7 
mm. long, chartaceous, the lemma ovate, acute, faintly 5-nerved, its palea equal to the 
lemma; lodicules absent; anthers 3, orange, 3.0-3.6 mm. long; style single, dividing into 2 
plumose short stigmas. 

Known from Costa Rica only about the hot springs of Las Hornillas, 
west face of Volcan Rincon de la Vieja, elevation 750 m. Southern 
Mexico to El Salvador; Costa Rica and Panama. 

Pennisetum distachyum Ruprecht, Bull. Acad. Roy. Sci. Bruxelles 
9:2:242. 1842. Gymnothrix distachya (Rupr.) Fourn., Mex. PL 2:48. 
1881. Figure 174. 

Tall vigorous perennial; culms arching, 2.5-3 m. long, in clumps from hard, knotty 
cormlike bases, the lower nodes rooting; internodes 3-6 mm. thick, glabrous; nodes 
appressed-hispid; sheaths mostly shorter than the internodes, glabrous except for the 
ciliate upper margins; ligule 1.5-3.5 mm. long, a short stiff membrane densely ciliate with 
stiff erect white hairs; larger leaf blades 17-45 cm. long, 15-35 mm. wide, flat, tapering to 
a narrow petiole-like base, glabrous to hirsute on both surfaces, the margins scabrous. 
Inflorescence of numerous terminal and axillary spikes, these borne on slender pedun- 
cles, usually several of unequal length from a single leaf axil; ultimate leaf blades of the 
flowering branches much reduced. Individual spikes 3-10 cm. long, 7-10 mm. thick, 
greenish or purplish; rachis slender, scabrous, flexuous, the minute scabrous stipes of 
the fascicles persisting on the rachis after they disarticulate. Fascicles each with a single 
spikelet, the bristles not conspicuous, mostly shorter than the spikelet except the in- 
nermost, which may be up to 20 mm. long. Spikelets narrowly ovate, acute to acuminate, 



466 FIELDIANA: BOTANY 

dorsally compressed, 4.0-6.2 mm. long, remaining attached to the fascicle; first glume 
minute, 0.5-1.2 mm. long, oblong-lanceolate, 1-nerved or nerveless; second glume ovate, 
acute, faintly 3-nerved, 1.8-2.5 mm. long; lower lemma 4.8-5.4 mm. long, narrowly 
ovate, acute or acuminate, scabrid toward the tip, faintly 5-nerved, the midnerve some- 
times suppressed; no palea or flower present; upper lemma 3.8-5.4 mm. long, similar to 
the lower, chartaceous, faintly 3-5-nerved, the margins thin and overlapping the edges 
of the palea, which is 3.7-4.7 mm. long; lodicules 2, truncate; anthers 3, purple, 1.3-1.8 
mm. long; styles naked at the base; stigmas 2, brown to purple. Chromosome number n 
= 18 from a Costa Rican specimen. 

Open, disturbed areas around San Jose, southern slopes of Volcan 
Turrialba, San Ramon. February to November, probably yearlong. 
Southern Mexico and Guatemala, Costa Rica. 

The nomenclature of this species is confused and citations of authors 
are often incorrect. Since P. distachyum was originally described by 
Ruprecht in 1842, Fournier (1881) cannot be cited parenthetically. 
Mrs. Chase believed the name should be applied to the species above, 
having short bristles. Her usage is followed. The type specimen 
(Galeotti 5680) was not seen by Chase, but was cited by Fournier, 
when he transferred the species to the genus Gymnothrix in 1881. 
Since descriptions are obscure and may refer to several species, de- 
finite application of the name awaits the examination of the specimen. 

Pennisetum purpureum Schum., Beskr. Guin. PL 64. 1827. Figure 
174. 

Tall stout perennial, forming large clumps; culms erect, to 8 m. tall, 1.0-2.5 cm. thick, 
solid or hollow, the bases often decumbent and rooting; branching sparse, mostly from 
the lower nodes; culms usually glabrous, glaucous, or sometimes pubescent near the 
summit; nodes not prominent, glabrous or sometimes appressed-hispid; sheaths glabrous 
or sometimes papillose-hirsute; ligule a minute membrane, bearing a dense row of long, 
stiff white hairs, in total 1.5-3.5 mm. long; leaf blades up to 125 cm. long and 4 cm. wide, 
glabrous to papillose-pubescent; midrib prominent beneath; margins strongly scabrous. 
Inflorescence a dense cylindrical spike of bristly fascicles, up to 30 cm. long, 1-2 cm. thick 
excluding the longer bristles; color golden yellow to purple; rachis cylindrical, densely 
clothed with white hairs, bearing the stubs of the stipes of the fascicles. Fascicles 
bearded at the base with short white hairs; bristles numerous, usually golden, scabrous, 
of varying lengths up to 10-15 mm. long; innermost bristle thicker, up to 40 mm. long, 
usually twice as long as the others; spikelets 1-5 per fascicle, the larger ones on minute 
pedicels above the bristles, the smaller or abortive ones on longer pedicels to 2 mm. 
Spikelets 4.5-7.0 mm. long, (except the abortive ones), dorsally compressed, narrowly 
ovate, caudate; remaining attached and falling with the fascicle; first glume absent or a 
minute rounded scale up to 0.7 mm. long; second glume ovate, 1-nerved, 1.5-2.6 mm. 
long; lower lemma 4.0-5.2 mm. long, narrowly ovate, acuminate, 3-nerved, the nerves 
scabrid; staminate flower of 3 stamens usually present; palea about equal to the lemma; 
upper floret 4.6-7.0 mm. long, the lemma shiny, the 5-7 nerves scabrid; palea about equal 
to the lemma; lodicules lacking; anthers 3, 2.7-3.6 mm. long; style 1, its upper part and 
the 2 stigmas plumose. 



BURGER: FLORA COSTARICENSIS 467 

Cultivated as a forage grass at low and medium altitudes up to 1,800 
m. and escaping on river banks and in open areas. Blooming July to 
November, probably yearlong. Native to tropical Africa, but widely 
cultivated in tropical regions of the world. Florida and the West In- 
dies; Guatemala; Costa Rica, to Brazil. The earliest specimen from 
Costa Rica was collected in 1924. An extensive synonymy is given by 
Stapf and Hubbard in Fl. Trop. Africa 9:1017-1018 (1934). Common 
names: Yerba elefante, Elefante, Gigante. 

Pennisetum setosum (Swartz) L. Rich., in Pers. Syn. PL 1:72. 
1805. Cenchrus setosus Swartz, Prodr. Veg. Ind. Occ. 26. 1788. Figure 
174. 

Vigorous perennial; culms 1-2 m. long, in clumps from hard, knotty cormose bases, 
bases sometimes decumbent, arching, branching from middle and upper nodes, 3-5 mm. 
thick, hollow, glabrous; leaf sheaths usually shorter than the internodes, glabrous or 
pilose along the upper margins, one side with a vertical auricle; ligule a short stiff 
membrane, densely ciliate with a row of long, stiff hairs, total length 1.5-2.7 mm.; 
sometimes a row of minute bristles on the collar; leaf blades acuminate, the larger ones 
15-55 cm. long, 4-18 mm. wide, mostly glabrous beneath, scabrid on margins and upper 
surface, with long, papillose-based stiff hairs on upper surface near the base, sometimes 
hirsute on both surfaces. Peduncles exserted on the main culm or on leafy branches, 
glabrous; inflorescences purplish, arching, 10-25 cm. long, 6-10 mm. thick excluding the 
bristles, 15-30 mm. including them; fascicles and bristles ascending in nature, often 
reflexed in herbarium specimens; fascicles densely crowded, sessile on the thin cylindri- 
cal, notched and grooved rachis; bristles of several unequal series, the outer ones very 
short, thin and delicate, the inner flattened and rigid near the base, conspicuously ciliate 
with delicate silky hairs about to the tip of the spikelet, the hairs of adjacent bristles 
becoming interlaced and tangled; inner bristles 6-12 mm. long, except the innermost one 
which is usually 16-22 mm. long, much exceeding the spikelet; fascicles with their in- 
cluded spikelets freely deciduous from the rachis. Spikelets one per fascicle, ovate, 
acute, 3.7-4.5 mm. long, sessile, remaining attached to the fascicle; first glume obsolete 
or up to 1 mm. long, oblong, nerveless; second glume 3.7-4.5 mm. long, 5-7-nerved, 
ovate, the tip 3-lobed; lower lemma 3.0-3.9 mm. long, ovate, 5-7-nerved, the tip lobed, 
the palea shorter; anthers 3 or 0; upper floret readily deciduous from the spikelet, 
perfect-flowered; lemma chartaceous, smooth and shining, ovate, acute, 2.2-3.0 mm. 
long, its flat margins covering the edges of the palea; anthers 3, yellow, 1.7-2. 1 mm. long; 
lodicules absent; styles 2, naked below; caryopsis elliptical, ca. 1.7 mm. long. Chromo- 
some number 2n = 53 from a Costa Rican specimen. 

Steep hillsides and road cuts, hilly savannas; western parts of the 
Meseta Central, San Mateo, San Ramon, Nicoya Peninsula, Canas, 
Boruca, Monteverde. Elevations 100-1,500 m. Blooming from late Oc- 
tober to February. Southern Florida; southern Mexico to Brazil; West 
Indies. 

Many cytological abnormalities were observed, indicating possible 
apomixis. 



468 FIELDIANA: BOTANY 

Pennisetum tempisquense Pohl, Fieldiana, Bot. 38:6. 1976. Figure 
176. 

Caespitose perennial; plants 39-100 cm. tall; culms erect, unbranched, densely clus- 
tered, glabrous, glaucous, rather thin-walled, the interior filled with parenchyma; nodes 
glabrous, constricted, dark; leaves ca. 7 per culm; sheaths mostly shorter than the 
internodes, compressed and keeled, glabrous and glaucous, the margin thin and mem- 
branaceous; ligule a short membrane, densely long-ciliate, 1.0-1.8 mm. long; leaf blades 
flat or folded, keeled near the base, firm, scabrous-margined, the base narrower than the 
summit of the sheath, glabrous and glaucous, 4.5-7.5 mm. wide, 8-22 cm. long, the 
uppermost shorter. Peduncle exserted; inflorescence a solitary terminal spike of fasci- 
cles, stiff and erect, whitish, 7-10 cm. long, 2.0-2.5 cm. thick, including the bristles; 
rachis ca. 1 mm. thick, longitudinally striate, densely short-hispid; fascicles borne on 
minute projections of the rachis, crowded, horizontally spreading, mostly 10-14 mm. 
long; bristles ca. 20 per fascicle, whitish, of varying lengths, the outermost 3-4 mm. long, 
the majority 8-10 mm. long, the innermost one longer and thicker, 12-17 mm. long, all 
straight, upwardly scabrous, attached to a short, rounded common stipe ca. 0.2-0.3 mm. 
long. Spikelet one per fascicle and sessile within it, narrowly ovate, acuminate, 5-6 mm. 
long; first glume ovate, 1.0-1.5 mm. long, acute to rounded, scarcely nerved, mem- 
branaceous; second glume, lower lemma, and upper lemma subequal, acuminate or awn- 
tipped; second glume 5.0-5.5 mm. long, striate, 7-nerved; lower lemma 5.7-5.9 mm. long, 
5-nerved, without a palea or flower; upper lemma 5.2-5.7 mm. long, faintly 5-nerved, the 
palea about equal, 2-nerved, acuminate; anthers purple, 1.2-1.5 mm. long; ovary with 2 
separate styles; stigmas purple; caryopsis oblong, tan, 2.1-2.2 mm. long. 

Known only from the type specimen, collected on a black gumbo clay 
flat, 8 km. N of Haciendo Palo Verde, Guanacaste, elevation 10 m., 
Pohl & Davidse 11725. The plants were past maturity when collected 
in late February. Chromosome number n = 36, originally published as 
P. nervosum in Pohl & Davidse, 1971. 

This species differs from the widespread P. complanatum (Nees) 
Hemsl. in its caespitose rather than rhizomatous character, in the 
fewer, more slender whitish bristles, the acuminate spikelets with 
sterile lower floret, and the separate styles. It differs from the South 
American P. nervosum in its smaller size, solid culms, smaller inflores- 
cences, fewer bristles, shorter spikelets with short first glume, and its 
chromosome number (n = 36, that of P. nervosum being n = 18). It 
appears similar to P. frutescens Leeke of southern South America, 
from which it differs in its solid culms, longer bristles, smaller size, 
lack of rhizomes, and different chromosome number. Pennisetum 
frutescens has 2n = 63 (Nunez, 1952). The specific name is derived 
from the Rio Tempisque, near the type locality. 

Pennisetum vulcanicum Chase, J. Wash. Acad. Sci. 13:363. 1923. 
Figure 174. 

Perennial, 1.0-1.5 m. tall, erect, the culms somewhat branched, glabrous; sheaths 
keeled, longer than the internodes, glabrous to papillose-pilose; leaf blades 20-45 cm. 




FIG. 176. Pennisetum tempisquense. A, inflorescence; B, growth habit; C, fascicle, D, 
pistil. 



469 



470 FIELDIANA: BOTANY 

long, 5-8 mm. wide, attenuate, papillose-pilose above. Inflorescence 10-17 cm. long, 
linear, cylindrical, 5-12 mm. thick, not including the bristles, up to 45 mm. including the 
longer bristles; fascicles crowded, sessile; rachis visible; spikelets 3-5 per fascicle, ses- 
sile; outer bristles short and fine, 3-4 mm. long; second series of bristles 10-12 mm. long, 
scabrous; inner series much fewer, thick and stiff, prominently long-ciliate on their lower 
halves; innermost bristle flattened, ca. twice as thick as the others and much longer, to 
2-5 cm. long; stipe short, hairy. Spikelets 6-9 mm. long, dorsally compressed; first glume 
ovate, apiculate, 1-nerved, 2.7 mm. long; second glume ovate, acute or blunt, 2-4- 
nerved, 3.0-3.5 mm. long; lower lemma 5.2 mm. long, ovate, 5-nerved, its palea 4.5 mm. 
long; anthers 3; upper lemma 5.7 mm. long, narrowly ovate, acuminate, 5-nerved, its 
palea 4.5 mm. long; anthers 3, orange, 2.7-3.0 mm. long; styles 2, separate, long and 
slender, naked below. 

This species is rare and little known. One specimen named by Agnes 
Chase (Gamier 822, from Managua, Nicaragua) had shriveled, non- 
opening anthers and collapsed pollen. Southwestern Mexico, 
Guatemala, El Salvador, Nicaragua. The only Costa Rican specimen 
determined by Chase was from Nuestro Amo (0. Jimenez 522}. This 
species is closely related to P. karwinskyi Schrad., which has been 
transferred by DeLisle to Cenchrus as C. multiftorus Presl. By 
growth habit and fascicle structure, it seems more closely related to 
Pennisetum. 

PENTARRAPHIS Humboldt, Bonpland, and Kunth 

Tufted small annual or perennial grasses; spikelets borne in fascicles on a slender erect 
flattened rachis and dropping from it whole; fascicle consisting of 1-2 spikelets, the lower 
sometimes reduced to a group of 2-4 stiff bristles; spikelets 2-flowered; first glume 
acicular, resembling the sterile bristles, the second subulate; lower floret perfect- 
flowered, its lemma 3-lobed; marginal lobes awnlike, arising about the middle of the 
length of the lemma; central lobe bifid, the 2 acuminate teeth arising at the base of the 
awn; nerves 3, all near the center of the lemma; second floret similar to the first but 
smaller, its flower abortive. 

Species 3, in Mexico, Central America, and Colombia. The genus is 
closely related to Bouteloua. (Choridoideae: Chlorideae.) 

Pentarraphis annua Swallen, Ceiba 4:286. 1955. Figure 177. 

Tufted annual; plants 10-25 cm. tall, the culms erect, in small tufts, branching from the 
base and lower nodes, glabrous, hollow, ca. 0.3 mm. thick; nodes enlarged, glabrous; 
prophylla 7-14 mm. long, exceeding the sheaths; sheaths glabrous, much shorter than 
the internodes; ligule ca. 0.3 mm. long, a minute ciliate fringe; blades 1-4 cm. long, ca. 1 
mm. wide, mostly involute, bearing a few scattered long hairs on the auricles and upper 
surface. Inflorescences terminal and axillary, the axillary ones of 1-2 partly concealed 
spikelets, the terminal inflorescence a slender spike, 2-3 cm. long, the rachis flattened, 
scabrous, terminating in a forked bristle-like rudiment; spikelet fascicles less than 10; 
fascicles consisting of a single fertile spikelet, subtended by several hispid bristles 
(rudimentary sterile spikelets), ca. 2.5 mm. long, the whole disarticulating from the 
rachis as a group with a bearded callus. Spikelets 8-9 mm. long, including the awns; first 




FIG. 177. Pentarraphis annua. A, inflorescence; B, apex of rachis with two appen- 
dages and a spikelet fascicle; C, spikelet fascicle; D, lemma. 



471 



472 FIELDIANA: BOTANY 

glume bristle-like, similar to the sterile bristles, hispid on its upper half, 2.0-2.5 mm. 
long; second glume subulate, 3.5-4.0 mm. long, tapering into a stiff scabrous awn; lower 
floret perfect-flowered, its callus bearded; lemma 3.2-3.5 mm. long, strongly 3-lobed; 
lateral nerves close to the midrib and extending into the acuminate teeth of the lemma; 
awn arising between the teeth, 4-5 mm. long, stiff and scabrous; back of the lemma 
bearing a transverse band of appressed-hispid hairs near the middle; margins of lemma 
produced into 2 stiff acuminate awnlike lobes, 4-5 mm. long, attached ca. one-third below 
the apex; palea 3.0-3.3 mm. long, bifid at the tip; anthers 3, purplish, 0.7-0.8 mm. long; 
caryopsis narrowly elliptical, free, 1.3 mm. long, tan; second floret similar to the first but 
smaller, its lemma 2.5-3.0 mm. long, glabrous, the flower apparently abortive. 

Rare; Hacienda Las Animas, Guanacaste. Our only specimen was 
collected from a dry tuff outcrop. December. Originally described from 
Honduras; Panama and Colombia. 

PEREILEMA Presl 

Short-lived annual grasses, developing at the beginning of the dry season; plants 
tufted, erect or the culms decumbent and rooting at the base, with erect flowering 
branches arising from the rooting nodes. Inflorescence a dense, lobed cylindrical panicle. 
Spikelets borne in dense fascicles crowded on the short erect branches; fascicles of 
several functional spikelets, with an involucre of reduced sterile spikelets, mostly in the 
form of short scabrid awns; spikelets 1-flowered; glumes equal, 1-nerved, awned from a 
bifid apex; floret disarticulating from the persistent glumes; lemma terete, long-awned; 
callus bearing straight erect hairs; palea about as long as the lemma. 

The genus appears close to Muhlenbergia, differing in the fascicle of 
sterile branchlets. (Chloridoideae: Sporoboleae.) 

KEY TO SPECIES OF Pereilema 

la. Upper leaf blades 5-8 mm. wide; awns straight; anthers 2, purple, 0.7-1.0 mm. 

long P. beyrichianum 

Ib. Upper leaf blades 2-3 mm. wide; awns flexuous; anthers 3, yellow, 0.5 mm. long 

P. crinitum 

Pereilema beyrichianum (Kunth) Hitchc., Contr. U.S. Natl. Herb. 
24:385. 1927. Muhlenbergia beyrichiana Kunth, Enum. PL 1:200. 
1833. 

Tufted annual; culms sometimes decumbent and rooting from lower nodes, 40-80 cm. 
long, mostly simple, 1-2 mm. thick, hollow, slightly scabrid-roughened, often reddish; 
nodes glabrous, not prominent; prophylls prominent, 2-3 cm. long, 2-toothed; leaf 
sheaths shorter than the internodes, minutely scabrid; ligule a thick brown membrane, 
0.7-1.0 mm. long; leaf blades 10-20 cm. long, 5-8 mm. wide, scabrid; auricles prominent, 
embracing the stem, ciliate. Peduncle mostly included, or exserted to 6 cm.; rachis of 
panicle angular, upwardly ciliate-scabrous; panicle single, terminal on the culms or on 
leafy branches arising from rooted lower nodes, 10-20 cm. long, 1-2 cm. wide, cylindrical, 
lobulate near the base; branches solitary, short, 1-3 cm. long, erect and appressed to the 
rachis, densely covered with fascicles of spikelets; fascicles dense. Functional spikelets 
terete; glumes subequal, 0.7-1.0 mm. long, oblong to broadly ovate, bearing an awn 3-4 



BURGER: FLORA COSTARICENSIS 473 

mm. long; lemma 1.0-1.5 mm. long, 3-nerved, lanceolate, tapering into a straight awn up 
to 2 cm. long; palea equal to lemma, tapering into a short awn tip; anthers 2, 0.7-1.0 mm. 
long, purple; sheaths and awn often reddish; awns bearing chloridoid microhairs. 
Chromosome number n = 40, from a Costa Rican specimen. 

Occasional in the Meseta Central near San Jose; Guadalupe, Rio 
Tiliri, Llano Grande, Puente Mulas; also near Santa Maria de Dota; 
brushy slopes; elevations 800-1,800 m. Late November to February. 
Guatemala and Costa Rica to northern South America. 

Pereilema crinitum Presl, Rel. Haenk. 1:233. 1830. Figure 178. 

Tufted annual, the culms sometimes decumbent and rooting at the lower nodes and 
bearing upright flowering branches from the rooted nodes; prophylls prominent, 2-5 cm. 
long, the keels bearing awns 2-4 mm. long at the tip; keels ciliate; culms 1 mm. thick, 
hollow, glabrous; nodes glabrous; sheaths mostly overlapping, scabrid; ligule 0.3-0.5 
mm. long, a minute lacerate membrane; leaf blades 5-15 cm. long, 2-3 mm. wide, gla- 
brous, tapering to a narrow base; auricles prominent, embracing the stem, ciliate. 
Peduncle ridged, angular, scabrid, included or exserted up to 5-10 cm.; panicles single, 
terminal, narrowly cylindrical, lobulate below, 5-13 cm. long, 2-3 cm. wide, including the 
awns; branches solitary, erect, ca. 1 cm. long, the lowermost often remote; spikelets 
borne in densely crowded fascicles; sterile bristles ca. 3 mm. long. Glumes of functional 
spikelets subequal, 1 mm. long, 1-nerved, oblong to ovate, bifid at the summit, with an 
awn ca. 2 mm. long; lemma 1.5 mm. long, lanceolate, 3-nerved, the lateral nerves 
marginal; callus hairs dense, erect, one-third to one-half as long as the lemma; lemma 
scabrid, tapering into a reddish, undulate awn 2-3 cm. long; palea equal to lemma; 
anthers 3, 0.5-0.7 mm. long, yellow. Chromosome number n = 10 from Costa Rican 
material. 

Scattered in the Meseta Central and a few other localities; Boruca, 
San Isidro de El General, Valley of Rio Grande de Tarcoles; mostly on 
steep exposed slopes, savannas, or road cuts; elevation 500-1,500 m. 
Guatemala and Honduras; Costa Rica to Ecuador. 

This species, like the preceding, develops very rapidly from seed at 
the beginning of the dry season and soon goes to seed and dies. 
November and December, rarely to February. 

PHALARIS Linnaeus 

Plants annual or perennial, caespitose or rhizomatous; inflorescence a dense cylindrical 
or ovoid terminal panicle; spikelets laterally compressed, the glumes equal, keeled, 
longer than and concealing the florets; florets 2 or 3, the lower 2 greatly reduced, 
appearing as little scales attached to the base of the fertile floret and disarticulating with 

it; fertile floret laterally compressed, rigid and shiny, awnless, glabrous or appressed- 

hairy. 

A genus of about 15 species of annual and perennial grasses, mostly 
native to the North Temperate Zone, with a few in southern South 
America. The genus belongs to the Pooid subfamily, and is probably 




.725? 



FIG. 178. Pereilema crinitum. A, inflorescence; B, fascicle of spikelets; C, glumes and 
floret. 



474 



BURGER: FLORA COSTARICENSIS 475 

most closely related to Hierochloe, from which it differs in its reduced 
lower florets. (Pooideae: Phalarideae.) 

KEY TO SPECIES OF Phalaris 

la. Rhizomatous perennial; leaves longitudinally green and white striped; inflorescences 
not produced under Costa Rican conditions P. arundinacea, f. picta 

Ib. Caespitose annuals; leaves green; inflorescences produced 2 

2a. Sterile lemmas 2, more than half as long as fertile floret P. canariensis 

2b. Sterile lemma 1, less than half as long as fertile floret P. minor 

Phalaris arundinacea L., Sp. PI. 55. 1753, f. picta (L.) Aschers. 
and Graebn., Syn. Mitteleurop. Fl. 24. 1898. 

This is a sterile form of the common reed canary grass of the north 
temperate zone. It is widely culivated as an ornamental in cooler 
climates. We have seen it cultivated in Los Yoses, but without 
inflorescences. 

Phalaris canariensis L., Sp. PI. 54. 1753. Figure 179. 

Tufted annual; culms erect, 30-100 cm. tall; panicle ovoid, 1.5-4 cm. long, up to 2 cm. 
wide, dense; spikelets broad, with a strongly winged keel; glumes 7-10 mm. long, with 
alternating whitish and green longitudinal stripes; fertile floret acute, 4.8-6.8 mm. long, 
densely appressed-pubescent; sterile florets 2, 2.5-4.5 mm. long, 1.4-1.7 mm. wide, 
sparsely pubescent. 

This species produces one of the types of "seeds" commonly fed to 
caged birds. For this reason, the plants may appear on waste heaps 
almost anywhere. Our single collection from Costa Rica was from a 
gutter along Avenida Central near La Luz, San Jose. 

Phalaris minor Retz., Fasc. Obs. Bot. 3:8. 1783. 

Caespitose annual; culms 20-100 cm. tall; panicle ovate-oblong, 1-6 cm. long, 1-2 cm. 
thick; glumes subequal, 4.0-6.5 mm. long, strongly keeled, and winged near the tip; 
fertile lemma 2.7-4.0 mm. long, 1.2-1.8 mm. wide, ovate, with a beaklike apex, yellow to 
gray-brown, shiny, appressed-pubescent; sterile floret one, usually 1.0-1.8 mm. long, 
appressed to the fertile floret, rarely very reduced and only 0.2-0.3 mm. long. 

A single specimen, probably of this species, was collected from a 
corn field near Potrero Cerrado, Prov. of Cartago, at 2,300 m. eleva- 
tion. The specimen lacks the basal portions and cannot be separated 
with complete certainty from P. aquatica L., a bulbous-based or 
rhizomatous perennial. Introduced from the Old World. Common 
name: Pasto San Juan. 

PHARUS Linnaeus 

REFERENCE: A. Prodoehl, Oryzeae monographice describuntur, Bot. 
Arch. l-J>harus X:247-252. 1922. 





FIG. 179. Phalaris canariensis. A, blooming culm; B, spikelet; C, two lower sterile 
lemmas and terminal fertile floret. 



476 



BURGER: FLORA COSTARICENSIS 477 

Caespitose or trailing perennial herbs; leaf blades large, borne on conspicuous 
pseudopetioles, lanceolate, elliptical, or obovate, inverted in position, the pseudopetiole 
having a 180-degree twist; veins diverging from the midrib and running straight to the 
margins of the blade; commisural veins conspicuous, the blades tessellate. Inflorescence 
a solitary terminal panicle, the rachis usually terminating as a thin sterile bristle, rarely 
tipped with a single spikelet. Spikelets unisexual, borne in pairs, the larger pistillate 
member of each pair subsessile, the small pedicellate staminate spikelet appressed to it, 
its pedicel arising at the base of the pistillate spikelet. Pistillate spikelets with 2 sub- 
equal usually many -nerved glumes, shorter than the floret; floret 1, readily disarticulat- 
ing above the glumes when mature; lemma cylindrical, straight or sigmoid, coriaceous, 
the margins inrolled over an equal linear palea, lemma terminating in a short conical 
beak; back of the lemma near the tip beset with uncinate hairs, these continuing to base 
of the lemma in some species; nerves 7, not conspicuous except at the contracted base; 
style 1, stigmas 3, hispid; caryopsis oblong, grooved on the palea side, ends blunt; 
embryo small, basal. Staminate spikelets borne on slender rigid pedicels which are 
shorter than the adjacent pistillate spikelet; glumes unequal, membranaceous, the first 
usually very short, the second shorter than the floret; lemma usually 3-nerved; 
membranaceous, laterally compressed, 3-5-nerved; palea slightly shorter, 2-nerved; 
stamens 6. 

The genus Pharus is confined to the tropics of the western hemi- 
sphere. The plants are unique in their broad, "commelinaceous" leaf 
blades, borne inverted and with strongly divergent veins. They may 
not be recognized as grasses by the casual observer. The panicles are 
rather fragile, readily breaking apart or separating from the plants. 
The rachis, panicle branches, and pistillate florets bear uncinate 
microhairs, those on the lemmas being conspicuous and serving to 
cause the mature pistillate florets to adhere to passing animals. (Bam- 
busoideae: Phareae.) 

KEY TO SPECIES OF Pharus 

la. Mature fruits (pistillate florets) at least 4 x as long as glumes, 20-23 mm. long, 

sigmoid, strongly divergent from branches of inflorescence P. cornutiis 

Ib. Mature fruits less than 3 x as long as glumes, 17 mm. or less long, straight or 

sigmoid, appressed to branches 2 

2a. Leaf blades narrowly lanceolate, 3 cm. or less wide, 5-10 x longer than wide; 

culms long-decumbent, rooting at lower nodes P. parvifolius 

2b. Leaf blades elliptical to obovate, larger ones more than 3 cm. wide, less than 5 x 

longer than wide; plants caespitose 3 

3a. Glumes of pistillate spikelets greenish or stramineous P. virescens 

3b. Glumes of pistillate spikelets brown 4 

4a. Pistillate floret uncinate-pubescent only on exposed portion above tips of 

glumes P. latifolius 

4b. Pistillate floret pubescent nearly to base 5 

5a. Fruit strongly sigmoid P. mezii 

5b. Fruit straight P. glaber 



478 FIELDIANA: BOTANY 

Pharus cornutus Hack., Oesterr. Bot. Z. 52:9:528. 1902. Figure 
180. 

Perennial, caespitose in small clumps; plants erect, 50-70 cm. tall; culms unbranched, 
ca. 3 mm. thick, solid, glabrous; sheaths mostly longer than the internodes, overlapping, 
glabrous or minutely puberulent; ligule a lacerate membrane, 1.5-2.0 mm. long; blades 
flat, dark green, slightly roughened, broadly obovate, abruptly narrowed to an acumi- 
nate tip, 6-14 cm. long, 3-8 cm. wide, borne on a puberulent pseudopetiole ca. 1 cm. long. 
Peduncle exserted 6-15 cm.; peduncle, rachis, branches and spikelets all more or less 
densely pubescent with uncinate hairs; inflorescence an open panicle, 15-20 cm. long and 
about as wide; branches solitary, the spikelets borne in pairs on secondary or tertiary 
branches; staminate spikelets appressed to the branches, the pistillate ones strongly 
divergent. Pistillate spikelets with short glumes, ca. one-fourth as long as the floret; first 
glume subulate, 2.7-4.5 mm. long, 3-nerved; second glume 4.5-5.5 mm. long, narrowly 
triangular, 5-nerved; floret linear-cylindrical, sigmoid, firm, light-colored, heavily beset 
with uncinate hairs above, less densely so to the base, 20-23 mm. long, 7-nerved, the 
apical beak small, palea linear, as long as the lemma, firm, 2-nerved; stigmas 3. Stami- 
nate spikelets borne on stiff erect pedicels, the tip of the spikelets reaching about to the 
tips of the glumes of the paired pistillate spikelet; first glume subulate, 1.5-3.0 mm. long, 
1-3-nerved; second glume ovate, 2.5-4.0 mm. long, 3-5-nerved; lemma thin, 3.0-5.0 mm. 
long, 3-nerved; anthers 6, 1.4-1.7 mm. long, yellow. 

Rare; lowland rainforests, 70-250 m. elevation. February to July. 
Guapiles, La Selva, Finca Chirripo, Tsaki, Villa Quesada, Osa Penin- 
sula. Endemic to Costa Rica. 

Pharus glaber H.B.K., Nov. Gen. & Sp. 1:196. 1816. Figure 180. 

Caespitose perennial; plants erect, 50-100 cm. tall, the culms unbranched, 3 mm. 
thick, solid, glabrous; leaf sheaths overlapping, glabrous; ligule membranaceous, 1.0-1.5 
mm. long; pseudopetioles 10-20 mm. long; leaf blades dark green, 11-22 cm. long, 3.5-4.5 
cm. wide, elliptical to narrowly obovate, tapering rather abruptly to a short triangular 
apex. Inflorescence solitary, terminal, 11-22 cm. long and about as wide, a very open 
panicle, the primary branches solitary; spikelets appressed to the secondary branches of 
the panicle; rachis and branches puberulent with uncinate hairs. Pistillate spikelets 
8.2-12.0 mm. long; glumes lanceolate, brown, rather blunt, the first 4.2-5.8 mm. long, 
3-nerved, the second 4.9-6.5 mm. long, 7-nerved; floret 8-12 mm. long, the lemma cylin- 
drical with inrolled margins, obscurely 7-nerved, the back covered with uncinate hairs 
nearly to the base; apex a straight conical glabrous beak 1.0-1.5 mm. long; palea equal to 
the lemma. Staminate spikelets paired with the pistillate, on pedicels appressed to the 
rachis and nearly as long as the pistillate spikelets, 2.5-2.7 mm. long, not disarticulating; 
first glume 1.0-1.7 mm. long, lanceolate, 1-nerved; second glume 2.0-2.4 mm. long, 
ovate, 3-nerved; lemma 2.5-2.7 mm. long, ovate, apiculate, faintly 3-nerved; palea ca. 
one-fourth shorter than the lemma; stamens 6, the anthers 0.9-1.1 mm. long. 

Rare; wet forests from 900-1,500 m. elevation; Sabalito, El Muneco, 
Volcan Rincon de La Vieja. November to March. Mexico and the West 
Indies to Colombia, Bolivia, and northern Argentina. 

Pharus latifolius L., Syst. Nat. ed. 10, 2:1269. 1759. Figure 180. 

Caespitose perennial, 30-100 cm. tall, forming open clumps, culms unbranched, gla- 




FIG. 180. Pharus species. P. latifolius: A, blooming plant; B, branch of panicle with 
two pistillate and a single staminate spikelet; P. glaber: C, two pistillate spikelets; P. 
carmdus: D, paired pistillate and staminate spikelets. 



479 



480 FIELDIANA: BOTANY 

brous, ca. 3 mm. thick, solid; nodes glabrous; sheaths rather loose, keeled, glabrous, 
overlapping; ligule an erose brown membrane, 0.5-1.0 mm. long; blades borne on 
pseudopetioles up to 7 cm. long; blades narrowly to broadly obovate, 15-30 cm. long, 3-8 
cm. wide, 3 to 5 x longer than wide, tapering rather abruptly to an acuminate apex. 
Inflorescence a solitary terminal panicle, up to 30 cm. long, broad, open, ca. as wide as 
long; rachis, peduncle, and branches puberulent with uncinate microhairs. Pistillate 
spikelets appressed to the branches, 10-17 mm. long; glumes brown, subequal, narrowly 
ovate, acute, rounded on the back, obscurely 7-nerved, ca. three-fourths as long as the 
floret; first glume 9-12 mm. long, the second 10-13 mm.; lemma stiff and cartilaginous, 
slightly curved, oblong-linear, rounded on the back, the margins involute over the palea 
and united just above the base; uncinate hairs abundant near the tip, extending down- 
ward about to the apex of the glumes, rarely further; glabrous conical beak of the lemma 
1.0-1.5 mm. long; palea membranaceous, linear, 2-nerved, about as long as the lemma; 
lodicules not evident; style elongate, fleshy, the 3 stigmas slender, white; caryopsis 
oblong, 9-10 mm. long, curved, rounded on the lemma side, grooved on the palea side. 
Staminate spikelets brown, membranaceous, 2.8-4.0 mm. long; first glume 0.4-1.2 mm. 
long, ovate, acute, 1-nerved; second glume 1.8-2.0 mm. long, ovate, 3-nerved; floret 1, 
not disarticulating; lemma ovate, acute, 5-nerved, glabrous; palea equal to the lemma, 
2-nerved; anthers 6, white, 1.4-1.7 mm. long. Chromosome number n = 12 from Costa 
Rican specimens. 

Common in rain forests of the Caribbean lowlands; Pacific lowlands 
of southern Puntarenas Province; scattered elsewhere; sea level to 650 
m. elevation. Blooming is apparently yearlong. Southern Mexico to 
Peru and Brazil; West Indies. 

Pharus mezii Prodoehl, Bot. Arch. 1:250. 1922. 

Erect caespitose perennial; plants 50-100 cm. tall; culms unbranched, 1-2 mm. thick, 
glabrous below, increasingly puberulent toward the inflorescence; leaves basal, the 
sheaths glabrous; ligule ca. 1 mm. long, brown, membranaceous; leaf blades elliptical or 
obovate, flat, 11-25 cm. long, 2.3-5.0 cm. wide, slightly scaberulous, conspicuously 
cross-veined. Peduncle of isotype in US from base of the plant, without cauline leaves. 
Inflorescence solitary, terminal, an open panicle, that of the isotype 13 cm. long, about as 
wide, open pyramidal; branches solitary, spreading (note: this inflorescence may be 
fragmentary). Spikelets paired, appressed along the branches. Pistillate spikelets 9-11 
mm. long; first glume 5.5-6.0 mm. long, 6-9-nerved, lance-ovate, acute, brown; second 
glume similar, 6.0-6.5 mm. long, 5-nerved; floret sigmoid, the lemma stiff, cylindrical, 
9-11 mm. long, the margins incurved over the palea; nerves obscure, numerous; tip a 
glabrous pointed beak 0.5-1.0 mm. long; dorsal surface of lemma covered with hooked 
hairs at least half way to the base. Staminate spikelets on stiff slender pedicels ca. 
two-thirds as long as the glumes of the associated pistillate spikelet, appressed to the 
pistillate spikelet; first glume ca. 0.7 mm. long, second glume 1.7-1.9 mm. long, acute; 
lemma 2.4-2.7 mm. long; anthers not seen. 

The type number, Biolley s.n. (Museo Nacional de Costa Rica 17326) 
was collected at Surubres, vertiente del Pacifico, altitude of 250 m., in 
February 1909. Costa Rica to Colombia. 

Pharus parvifolius Nash, Bull. Torrey Bot. Club 35:301. 1908. P. 



BURGER: FLORA COSTARICENSIS 481 

latifolius L., var. angustifolius (Nash) Prodoehl, Bot. Arch. 1:250. 
1922. 

Perennial; culms extensively trailing, branching freely from the nodes of the prostrate 
portions, the erect branches up to 1 m. long, unbranched; culms 3-6 mm. thick, solid, 
glabrous; nodes glabrous; sheaths glabrous, mostly overlapping; ligule a lacerate- 
ciliolate membrane, 0.5-1.0 mm. long; blades borne on margined pseudopetioles 6-30 
mm. long; blades dark green, glabrous, but roughened beneath by the conspicuous 
commissural veins, 5-10 x longer than wide, 10-28 cm. long, 2.0-3.0 cm. wide, flat. 
Peduncle exserted up to 15 cm.; inflorescence an open panicle, up to 30 cm. long; 
branches mostly solitary; spikelets borne on second- or third-order branches, lying 
parallel to the branches. Pistillate spikelets subsessile; glumes subequal, ca. 7 mm. long, 
glabrous, lanceolate, 5-nerved; floret 12-15 mm. long, nearly straight, the lemma ter- 
minating in a glabrous conical beak ca. 1 mm. long; back of lemma covered with abundant 
uncinate hairs, less densely so nearly to the contracted base; nerves 7; margins incurved, 
spread apart in fruit, exposing a firm glabrous linear palea of about the same length; 
caryopsis free from the bracts, oblong, tan to brown, blunt at apex, tapering to a point at 
the base, convex on the lemma side, shallowly grooved on the palea side, 9-11 mm. long. 
Staminate spikelets borne on stiff erect pedicels appressed to the rachis and almost as 
long as the glumes of the adjacent pistillate spikelet; staminate spikelets 3.0-3.7 mm. 
long, narrowly ovate; first glume nerveless, deltoid to lanceolate, 0.7-1.4 mm. long, less 
than half as long as the spikelet; second glume and lemma subequal, 3-nerved, 3.0-3.7 
mm. long; palea equal to lemma, 2-nerved; stamens 6, the anthers 1.8-1.9 m. long, tan. 
Chromosome number n = 12 from a Costa Rican specimen. 

Rare; undisturbed moist forests, 500-1,200 m. This species is com- 
mon in the forested canyon of the Rio Reventazon at the CATIE at 
Turrialba. It has also been collected in the General Valley, at Finca 
Las Cruces near San Vito de Java, and in a few localities on the 
volcanoes of Guanacaste. It is abundant in moist forests above 1,100 m. 
on Volcan Rincon de la Vieja on Hacienda Guachipelin, and on Volcan 
Tenorio near Tierras Morenas. Blooming is apparently restricted to 
the dry season. Southern Mexico to Panama; West Indies and northern 
South America. 

Pharus virescens Doell in Mart., Fl. Bras. 2:21. 1871. 

Perennial; bases decumbent and rooting; erect portions of culms to 1 m. tall, un- 
branched; culms solid, glabrous; sheaths overlapping, glabrous; ligule a ciliate mem- 
brane, ca. 1 mm. long; pseudopetioles broadly margined, elongated, scarcely dif- 
ferentiated from the sheath; blades large, light green, narrowly obovate, tapering rather 
abruptly to an acuminate apex, length 25-33 cm., width 4-7 cm. Peduncle ridged and 
grooved; panicles solitary, terminal, large and open, up to 30 cm. long and ca. as wide; 
spikelets appressed to secondary or tertiary branches; rachis and branches scabrous and 
beset with uncinate hairs; spikelets paired, or some of the pistillate ones solitary. Pistil- 
late spikelets subsessile; glumes subequal, greenish or stramineous, not brown, nar- 
rowly triangular, the tip rather blunt; first glume 10-11 mm. long, 5-nerved; second 
glume similar, 10-12 mm. long; floret straight, cylindrical, flattened on the back, 13-15 
mm. long, the terminal beak narrow, glabrous, 1.0-1.5 mm. long; back of lemma covered 
with uncinate hairs two-thirds of way to the base, these especially numerous near the 



482 FIELDIANA: BOTANY 

margins; palea equal to the lemma, linear, 2-nerved. Staminate spikelets borne on slen- 
der appressed pedicels from the base of the pistillate ones, the pedicel up to 10 mm. long; 
spikelets laterally compressed, 2.5-4.2 mm. long; first glume ca. 1.2 mm. long, 1-nerved, 
ovate, acute; second glume 2.5-4.2 mm. long, 3-nerved, narrowly ovate, acute; lemma 
2.5-2.7 mm. long, narrowly ovate, 3-nerved, its palea equal; anthers 6, purple, 0.7-0.9 
mm. long. One staminate spikelet with 2 florets and a total of 8 anthers was found. 

Rare, lowland forests; apparently blooming from January to March. 
El General, Shirores, Hamburg Finca. Guatemela to Peru and Brazil; 
Hispaniola. 

PHRAGMITES Adanson 

REFERENCES: H. J. Conert, Die Systematik und Anatomic der 
Arundineae, 1-208. Cramer. Weinheim. 1961. W. D. Clayton, The cor- 
rect name of the common reed, Taxon 17:168-69. 1968. E. D. Voss, 
Additional nomenclatural and other notes on Michigan monocots and 
gymnosperms, Michigan Bot. 11:26-37. 1972. 

Tall stout perennial reeds with plumy panicles; spikelets several-flowered; glumes 
narrow, the first 3-nerved, the second 5-nerved, shorter than the florets; an evident 
internode between the first and second glumes; disarticulation above the first floret and 
at the base of the rachilla internode beneath each succeeding floret; rachilla internodes, 
except the lowermost, covered with numerous long, silky hairs; lowermost floret persis- 
tent with the glumes, its lemma 5-nerved, the flower staminate; other florets with 
3-nerved lemmas and perfect flowers; lemmas slender, acuminate, glabrous; paleas much 
shorter than the lemmas; uppermost florets shorter than the lower ones, so that the tips 
of all lemmas are at approximately the same level. 

Phragmites is a genus of about four species, widespread in the 
temperate and warmer zones of the world. It is most closely related to 
other large reeds such as Arundo, Gynerium, and Cortaderia. (Arun- 
dinoideae: Arundineae.) The genus Phragmites is known from all the 
continents except Antarctica. Authors recognize from one to several 
species, which appear to be poorly defined. 

Phragmites australis (Cav.) Trin. ex Steud., Nom. Bot. ed 2, 2:324. 
1841. Arundo australis Cav., Ann. Hist. Nat. 1:100. 1799. Phragmites 
communis Trin., Fund. Agrost. 134. 1820. Arundo phragmites L., Sp. 
PL 81. 1753. Figure 181. 

Plants forming large colonies; culms erect, unbranched except when injured, 2-8 m. 
tall, up to 2 cm. thick, hollow, glabrous; rhizomes abundant, longitudinally ridged, 
hollow, 1-2 cm. thick; leaves numerous, the sheaths usually overlapping, glabrous except 
for auricular hairs 5-7 mm. long; blades glabrous, 30-50 cm. long, 15-25 mm. wide, flat; 
peduncles mostly included; panicle solitary, rather dense, up to 45 cm. long, pyramidal, 
drooping; lower branches numerous, whorled, naked at the base; spikelets very numer- 
ous, compactly arranged on the outer portions of the branches, wedge-shaped, 11-15 
mm. long; first glume 3.8-5.2 mm. long, 3-nerved, ovate, acute; second glume 5.5-6.5 
mm. long, 5-nerved, ovate, acute; florets 3-5, the lowermost ones 9-10 mm. long, the 







FIG. 181. Phragmites australis. A, panicle; B, leaf bases with auricular hairs; C, 
rhizome; D, spikelet. Drawn from fertile material. 

483 



484 FIELDIANA: BOTANY 

uppermost much shorter; lemmas lance-attenuate; paleas 2-3.5 mm. long; anthers 1.4-2 
mm. long, yellow. Chromosome count 2n = 72 obtained from vegetative internodes of 
the sterile strain from Trinidad. 

This species is rare in Costa Rica and uncommon in Central America 
in general. We have specimens from Trinidad, Laguna Bonilla, the 
Limon area, and Finca Las Cruces near San Vito de Java. The colony 
from Trinidad, on the south slope of Volcan Turrialba, fills a large 
marsh. Although the plants are very tall, they never bloom in nature. 
We have been able to induce the formation of sterile inflorescences in 
the greenhouse at Iowa State in February 1973 and July 1975. No 
fertile spikelets occurred in any of these inflorescences. Most spikelets 
were minute rudiments, the largest about 5 mm. long. Another sterile 
colony occurs on Finca Las Cruces. The other collections from Costa 
Rica bear spikelets that are malformed or sterile in varying degrees, 
and such sterility is extremely common in this species in Central 
America. The description given above is taken from Central American 
specimens, and may not apply closely to material from the temperate 
zone. Various chromosome numbers have been reported for this 
species. 

PHYLLOSTACHYS Siebold & Zuccarini 

REFERENCE: F. A. McClure, Bamboos of the genus Phyllostachys 
under cultivation in the United States, U.S.D.A. Agriculture Hand- 
book 114. pp. 1-69. 1957. 

Bamboos of slender growth habit; rhizomes extensive; culm internodes hollow, D- 
shaped in cross section, flattened above the insertion of the branch buds; primary 
branches typically 2 at each node, unequal, sometimes a third smaller one present; culm 
sheaths papery, the apex rounded to a narrow reduced blade; foliage leaf blades 
pseudopetiolate, readily deciduous; leaf blades small, flat, tessellate. Inflorescence a 
panicle whose branches bear clustered pseudospikelets (complex bracted structures that 
resemble spikelets, but are internally branched into 1 or more true spikelets). Pseudo- 
spikelets enveloped in conspicuous inflated sheaths that bear reduced blades and enclose 
2-3 spikelets. Spikelets bearing 1-3 many-nerved empty bracts (glumes) at the base; 
florets 1-3, the terminal one rudimentary; lemmas acuminate, many-nerved; palea about 
equal to the lemma, 2-keeled, many-nerved; lodicules 3, flat, vasculated; stamens 3; 
ovary with a single style and 3 stigmas. 

Phyllostachys is a small Asiatic genus, important for several culti- 
vated species, used for ornament, fishpoles, timber, paper, and edible 
shoots. (Bambusoideae: Arundinariae.) 

Phyllostachys aurea A. & C. Riviere, Bull. Soc. Natl. Acclim. 
France, Ser. 3:716. 1878. P. bambusoides Sieb. & Zucc., var. aurea 
(A. & C. Riv.) Makino. Figure 182. 

Long-lived bamboo; rhizomatous; clumps dense to open; culms up to 10 m. tall, erect or 




FIG. 182. Phylloatachya aurea. A, leafy branch; B, culm sheath; C, pseudospikelet. 



485 



486 FIELDIANA: BOTANY 

slightly arching; internodes 1-4 cm. thick, hollow, glabrous, D-shaped in cross section; 
nodes prominent; some culms, but not all, have a succession of several short internodes 
near the base; culms branching freely from middle and upper nodes, with usually 2 
unequal branches at each node, sometimes a third smaller one; branches slender but 
stiff, rebranching; main culm sheaths up to 20 cm. long, the margins ciliate; apex 
rounded, bearing a narrow linear reduced blade; foliage leaves borne on minor branch- 
lets, usually 3-8 per branchlet; leaf sheaths ciliate on the margin; oral setae sometimes 
present; ligule a short, thick ciliolate membrane, puberulent on the back, 0.7-0.8 mm. 
long; external ligule a minute thick rim; leaf blades flat, tessellate, 4-10 cm. long, 5-16 
mm. wide, ovate 5-6:1, abruptly acuminate, base rounded to a short flattened 
pseudopetiole; margins scabrous; lower surface puberulent near the base, sometimes all 
over the surface. Inflorescence a terminal panicle of clustered pseudospikelets, up to 
35-50 cm. long, open, with rigid ascending or spreading branches; much smaller inflores- 
cences occur on sheared specimens. Pseudospikelets numerous, ascending and overlap- 
ping, often with small rigid bracts at their bases; spikelets concealed by inflated external 
bracts, bearing reduced leaf blades, spikelets 1-several in each pseudospikelet. Spikelets 
usually with a single acuminate, 9-11-nerved cylindrical glume, ca. as long as the 
spikelet; some spikelets have 2 glumes; florets 1-2; rachilla internode supporting the 
lowermost floret thickened to the apex, sometimes puberulent; disarticulation at the 
base of the lowermost floret; florets cylindrical, acuminate, the lemma 9-11-nerved, 
enwrapping the palea; rachilla internode prolonged 4-5 mm. beyond the ultimate floret 
and bearing a rudiment at its apex; palea ca. as long as the lemma, several-nerved, 
clasping the rachilla internode, the keels prolonged as 2 short awns; lodicules 3, flat, 
vasculated; anthers 3, yellow, 12-13 mm. long; ovary bearing an elongated style with 3 
short stigmas at its apex. Chromosome number n = 24 from a Costa Rican specimen. 

This is the common yellow-stemmed bamboo, often used for sheared 
hedges or allowed to grow naturally as a tall screen. It occurs com- 
monly around San Jose and is occasionally found blooming. Flowering 
plants have been seen in the Parque Bolivar, around the zoological 
garden. A sheared hedge along Calle 33, S of La Luz bloomed in 1968, 
without death of the plants. The individual inflorescences were small 
and leafy. A tall clump along. Hwy. 204 N of the Colegio de Abogados 
had culms 4-5 m. tall which were in flower in December 1968. These 
culms were dying after flowering. Flowering habits of this species in 
the western hemisphere are not well known, but our experience in 
Costa Rica suggests that at least minimal blooming, without cane 
death, may be fairly frequent. A large blooming panicle from Virginia, 
collected by Dr. Allard, bears the notation that the plant had been 
transplanted 15 years before and had remained vegetative for that 
period. The species is native to China. 

POA Linnaeus 

Plants perennial or rarely annual, caespitose or rhizomatous; culms unbranched. 
Inflorescence a terminal panicle, the branches usually clustered. Spikelets several- 
flowered, laterally compressed, disarticulating above the glumes and between the 
florets; glumes shorter than the florets, the first 1-nerved, the second usually 3-nerved; 



BURGER: FLORA COSTARICENSIS 487 

lemmas folded, 5-nerved, acute or blunt, awnless; midnerve, marginal and intermediate 
nerves often pubescent; the blunt callus in some species bearing a tuft or web of crimped, 
cottony hairs. 

A large genus of temperate and arctic zones of the world, poorly 
represented in the tropics. Many of the species are highly apomictic 
and extremely variable. The genus is related to Festuca, from which it 
differs in the rather blunt, awnless lemmas and in the leaf tips, which 
are blunt and cupped like the prow of a boat. (Pooideae: Poeae.) 

KEY TO SPECIES OF Poa 

la. Plants rhizomatous; lemmas bearing elongated web of cottony hairs and also pubes- 
cent on keel, marginal, and intermediate nerves; pastures on volcanoes 

P. pratensis 

Ib. Plants not rhizomatous; lemmas variously pubescent, with or without a web. . . 2 

2a. Basal foliage stiff and erect, the elongated leaf blades folded, sharp-tipped; 

glumes nearly as long as spikelet; lemmas densely scabrous with short, stiff 

hairs; summit of Chirripo Grande P. chirripoensis 

2b. Foliage soft, leaf blades flat; glumes shorter than lowermost lemma; lemmas not 

densely scabrous; plants of middle altitudes 3 

3a. Lemmas ciliate on keel, marginal, and intermediate nerves; no cottony web present; 

low, spreading plants, 5-35 cm. tall P. annua 

3b. Lemmas ciliate on keel, rarely also on marginal nerves; cottony web present at least 

on lowermost lemma; plants usually erect, 20-100 cm. tall 4 

4a. Ligules 4-10 mm. long; lower branches of panicles 3-7 per node . . P. trivialis 
4b. Ligules less than 2 mm. long; lower panicle branches 1 or 2 per node 

P. talamancae 

Poa annua L., Sp. PL 68. 1753. Figure 183. 

Duration annual or indefinite; plants 5-35 cm. tall, erect and tufted, or in wet habitats, 
becoming long-decumbent and rooting at the nodes; branching from the base or from the 
nodes of decumbent stems; prophylla prominent, up to 2.5 cm. long; culms soft, glabrous; 
leaf sheaths mostly overlapping, glabrous; ligule a thin white membrane, 1-4 mm. long, 
decurrent on the sheath margins; blades 0.5-11.0 cm. long, 1-4 mm. wide, soft, flat, 
blunt-tipped, the uppermost much reduced. Plants of wet habitats have much larger 
leaves than those of drier sites. Peduncle included or exserted up to 11 cm.; inflorescence 
a solitary terminal panicle, 2-7 (11) cm. long, pyramidal, the branches solitary or paired, 
the spikelets densely clustered near their tips. Spikelets laterally compressed, green or 
purplish, 4.0-5.5 mm. long, disarticulating above the glumes and between the florets; 
first glume ovate, acute, 1-nerved, 1.5-2.7 mm. long; second glume obovate, acute, 
3-nerved, 2.2-3.3 mm. long, shorter than the lowermost floret; florets 2-6; lemmas 2.6-3.8 
mm. long, ovate, rather blunt, often bronzy near the apex; nerves 5, all silky-pubescent, 
the internerve area near the base also sometimes pubescent; palea slightly shorter than 
its lemma, silky-ciliate on the keels; anthers 3, yellow, 0.9-1.2 mm. long. Chromosome 
number n = 14 from Costa Rican specimens. 

Open moist areas, ditches, pastures; Meseta Central, Poas, Irazii, 
Cerro de la Muerte; elevations from 1,100 to 3,400 m. Apparently 
blooming yearlong. Worldwide in cool climates; apparently introduced 



488 FIELDIANA: BOTANY 

in the New World. In North America, it extends southward to Volcan 
Chiriqui in Panama. 

Poa chirripoensis Pohl, Fieldiana, Bot. 38:10. 1976. Figure 184. 

Perennial; densely caespitose; culms erect, unbranched, 37-58 cm. tall, hollow, gla- 
brous, elliptical in cross section; nodes dark, not prominent; basal foliage abu