Brittonia, 34(2), 1982,pp. 220-224. O 1982,by the New York BotanicalGarden, Bronx, NY 10458 THE D E V E L O P M E N T OF THE FRUITS A N D SEEDS OF C A M P O M A N E S I A (MYRTACEAE) LESLIE R. LANDRUM a Landrum, Leslie R. (New York Botanical Garden, Bronx, NY 10458). The development of the fruits and seeds of Campomanesia (Myrtaceae). Brittonia 34: 220-224. 1982.--The glandular nature of the "seed coat" has long been the most important taxonomic character defining the genus Campomanesia. It is shown here that the structure, which has been taken for the "seed coat," is actually the locular wall. The development of the ovaries and seeds of Campomanesia is discussed and illustrated. Three characteristics of Campomanesia are identified as distinguishing it from other genera of the Myrtaceae: (1) the abortion of all but one ovule in each fertile locule; (2) the protective, glandular locular wall that serves as a false seed coat; and (3) the large number of locules in the ovaries. Reasoning is presented to explain the possible sequence of evolutionary origin of these three characteristics. The genus Campomanesia (Myrtaceae) is a group of trees and shrubs that ranges from northern Argentina to Trinidad, and from the coast of Brazil to the Andes of Peru, Ecuador, and Colombia. The g e n u s is a member of the tribe Myrteae, the fleshy fruited Myrtaceae. Berg (1855-1856, 1857-1859), the most important monographer of the American Myrtaceae of the 19th century, divided what I consider to be Campomanesia into six genera (Campomanesia Ruiz & Pav6n, Acrandra Berg, Abbevillea Berg, Britoa Berg, Lacerdaea Berg, and Paivaea Berg) and among these he recognized ca 100 species. After considerable study of many herbarium specimens, it is my opinion that there are only about 30 species in the complex. This systematic study of Campomanesia has involved the dissection of numerous flowers and fruits. Through these investigations, it has become clear that the development of the fruit and seeds of Campomanesia has been misunderstood ever since the original description of the genus by Ruiz and Pav6n in 1794. It is the purpose of this paper to discuss briefly the interpretation of these structures by previous workers, and to clarify the situation as I now understand it. Interpretations of Earlier Workers Ruiz and Pav6n stated that the ovary of Campomanesia was unilocular and that the fruit contained 10-12 seeds arranged in a circle around a central axis or " r e c e p t a c u l o . " They apparently did not dissect y o u n g ovaries; it is clear that young ovaries are multilocular. Ruiz and Pav6n described the testa of the seeds as being "granulosis resiniferis." By 1828 A. P. de Candolle had recognized that the ovaries of Campomanesia were 7-10-1ocular, and that each locule contained ca 9 ovules. But he continued to describe the seeds as had Ruiz and Pav6n, as a single circular series of 10-12 with a granular-resiniferous testa. Berg (1855-1856, 1857-1859) described the ovary, fruit, and seeds of Campomanesia (and the other segregate genera for which he had adequate material) much as had de Candolle. He said that in Campomanesia the ovary was 4-111ocular, that the locules were multiovulate, that the ovules were attached to the internal angle of the locule in two rows, that the seeds were attached in a circular series, and that the testa was " m e m b r a n a c e a verrucose-glandulosa." 1 B. A. Krukoff Research Associate. 1982] LANDRUM; CAMPOMANESIA 221 More recent workers (Bentham & H o o k e r , 1865; Niedenzu, 1893; McVaugh, 1968; Rotman, 1976; Legrand & Klein, 1977) have described the ovary, fruit, and seeds of Campomanesia in essentially the same way as did de Candolle and Berg. The "verrucose-glandular testa" of Campornanesia has long been the most valuable characteristic in defining the genus. McVaugh (1968) has stated that " n o single character of Campomanesia, with the possible exception of the thickness and texture of the testa, permits ready assignment of an unknown species to this genus rather than to e.g. Psidium." The new findings presented here sharpen considerably the distinction between Campomanesia and all other genera of the Myrtaceae. Development of the Fruit and Seeds of Campomanesia The ovaries of Campomanesia have (3) 4-18 locules. Each locule has 4-22 ovules arranged in two longitudinal rows. In each locule zero, one, or rarely two ovules develop. The walls of the locules become thickened and glandular (i.e. they contain cavities with a resinous substance inside) as the o v a r y matures. If an ovule develops in a locule the walls apparently serve as a protective false " s e e d - c o a t " that has been mistaken for the true seed-coat (Fig. I A - E ) . It is common for some of the locules to have no ovules mature. Nevertheless the walls of the sterile locules also b e c o m e glandular. In some species the wall of the locule is verrucose (e.g., Campomanesia guaviroba (DC.) Kiaerskou, Fig. 1E) whereas in others it is smooth (e.g., C. guazumaefolia (Camb.) Berg, Fig. 1D). Thus the wall is not always verrucose as has been previously stated. In the mature locule it is very difficult to separate the delicate, membranous true seed-coat from the locule wall. I have not been able to find aborted ovules in a mature locule, but in an immature fruit (ca 1A- 89grown) one can generally separate the developing ovule from the aborted ones (Fig. I B). In only one specimen of the several examined have I found mature locules with two mature embryos. The characteristic of the locule-wall serving as a false seed-coat in Campomanesia is apparently unique in the Myrtaceae. The genus Pilidiostigma of Australia has been described as having a "glandular-tuberculate" testa (Scott, 1979) but my examination of two specimens indicates that in Pilidiostigma it is indeed the testa that is "glandular-tuberculate" and not the locule-wall. Curiously enough George Gardner seems to have understood the seeds and fruits of Campomanesia as far back as 1837. On the label of the type of C. hirsuta at Kew he wrote of the ovaries: "in 6 which I examined -15-16-18-16-16-14celled about 10 s e e d e d " [i.e. about 10-ovulate]; and of the fruits he wrote: " a b o u t 16 celled, cells by abortion 1 seeded." But Gardner did not mention the abortion of ovules or the fact that the mature locules are 1-seeded when he published C. hirsuta in 1843. More recently drawings of J. F. Toledo have posthumously been published by H a n d r o (1953). One drawing is of the genus Paivaea (=Campomanesia) in which abortive ovules are indicated, but no explanation accompanies the drawings. Campomanesia The definitive characteristics of Campomanesia are rather peculiar and stimThe Definitive Characteristics of ulate one to speculate as to the sequence of their origin. First is the systematic abortion of all but one of the ovules in each of the locules. Ovule abortion is common in Myrceugenia (Landrum, 1980; 1981), Eugenia, Myrcianthes, and apparently in many other genera with numerous ovules. But I know of no other 222 BRITTONIA 2mm I [VOL. 3 4 I 5ram | I 2mm I I lOmm I i L 10ram FI6. 1. Ovaries and ovules of Campomanesia. A. Cross section of a floral ovary of C. guazumaefolia (Camb.) Berg (Klein 3196). B. Longitudinal section of an immature fruit of C. guazumaefolia showing two locules, each with one developing ovule and other aborted ovules (Smith, Reitz & Pereira 9669). C. The ovules of one of the locules in B; X = developing ovule; Y = aborted ovule; Z = placenta. D. Cross section of a mature fruit of C. guazumaefolia with 14 locules, three of which contain a seed (Smith & Klein 11507). E. Cross section of a mature fruit of C. guaviroba (DC.) Kiaerskou with 13 locules, 8 of which contain a seed. The embryo of Campomanesia is spiral so that in cross section it is usually cut in more than one place. All drawings were made by first taking photographs and then tracing the photographs. 1982] LANDRUM: CAMPOMANESIA 223 genus of the M y r t e a e in which all but one ovule in each locule is normally aborted, nor does McVaugh (1968) mention such a genus. Abortion is p e r h a p s initiated by the parent plant in order to concentrate resources on the remaining ovule. The second character, found only in Campomanesia, is the glandular wall of the locule. The fruits of Campomanesia are fleshy and often large, up to ca 7.5 cm in diameter according to Gardner (1843). I think that birds and m a m m a l s must tear the fruits apart to eat them. The substance in the glands of the loculewalls smells similar to turpentine and p r e s u m a b l y tastes the same. Animals eating the fruits would p r o b a b l y carefully avoid the locules. The third characteristic is the large n u m b e r of locules found in most of the species of Campomanesia. In the majority of the Myrteae the n u m b e r of locules in the ovary is 2 or 3. In Psidium there are usually 3-4 (rarely 2-7) and in Calycolpus 4-5 (McVaugh, 1968). In Campomanesia the n u m b e r of locules is only occasionally as few as 3 and is normally 4-18. In about one half of the species that I have examined, I have n e v e r found fewer than 9 locules. In only 4 species have I found as few as 4 locules. The variation in the n u m b e r of locules per o v a r y a m o n g the species of Campomanesia seems to be correlated with flower size. What would h a v e been the order of acquisition of these characteristics? It seems logical that the reduction of the n u m b e r of seeds per locule to one must have preceded the transformation of the Iocule-wall to a glandular protective covering, since the locule with its contents is the apparent propagule in Campomanesia. If the Iocule were to normally contain more than one seed, there would be u n n e c e s s a r y competition a m o n g the seedlings. Once the combination of characters, (a) one seed per locule, and (b) a glandular p r o t e c t i v e locule-wall, b e c a m e established, the only way to increase the number of propagules in a fruit would be to increase the number of locules. There is an obvious advantage in increasing the n u m b e r of locules in a fruit if each serves as a propagule, but the advantage is not obvious if the locules do not serve as propagules. Thus I hypothesize that the order of acquisition of the definitive characteristics of Campomanesia was (a) abortion of all ovules except one in each locule; (b) transformation of the wall of the locule into a glandular protective tissue; and (c) an increase in the n u m b e r of locules per ovary. In Campomanesia it is u n c o m m o n for seeds to develop in all the locules of the ovary, and my observations indicate that a b o u t one half the time only 1-3 seeds reach maturity. W h y this should h a p p e n I do not know. Perhaps the process of abortion is sufficiently imprecise that all the ovules in a locule are sometimes aborted. Or alternatively it m a y be a d v a n t a g e o u s to the plant to concentrate resources on a few seeds under some circumstances. Acknowledgments I am very grateful to the following institutions for sending me material on loan for my studies of Campomanesia: A, C, C A Y , C O L , C T E S , F, G, G H , H , K, L E , L I L , M, M B M , MG, M I C H , MO, RB, SI, SP, UB, U C , U S , and W. I also thank two a n o n y m o u s reviewers who offered m a n y helpful suggestions. Literature Cited Bentham, G. J. D. Hooker. 1865. Genera plantarum 1(2): 712. Berg, O. 1855-1856. Revisio Myrtacearurn Americae. Linnaea 27: 1~,72. --. 1857-1859. Myrtaceae. In: Martius, C. F. P. von, Flora Brasiliensis 14(1):1-655. Candolle, A. P. de. 1828. Myrtaceae. Prodromus systematis naturalis regni vegetabilis 3: 207-296. 224 BR1TTONIA [VOL. 34 Gardner, G. 1843. Contributions towards a flora of Brazil, Part II, Plants from the Organ Mountains. London J. Bot. 2: 32%355. Handro, O. 1953. Novidades taxonomicas de J. F. Toledo. Arg. Bot. Estado $5.o Paulo 3(2): 63-97. Landrum, L. R. 1980. A monograph of the genus Myrceugenia (Myrtaceae). Ph.D. thesis, University of Michigan, Ann Arbor. 1981. A monograph of the genus Myrceugenia (Myrtaceae). Flora Neotropica 29: 1-137. Legrand, C. D. & R. M. K~ein. 1977. Campomanesia. Flora Ilustrada Catarinense. Mirtficeas. 573-623. McVaugh, R. 1968. The genera of the American Myrtaceae - - An interim report. Taxon 17: 354--418. Niedenzu, F. 1893. Myrtaceae. In: A. Engler and K. Prantl. Die Nat/irlichen Pflanzenfamilien 3(7): 57-105. Rotman, A. D. 1976. Revisi6n del g6nero "Campomanesia" en la Argentina. Darwiniana 20: 327-340. Ruiz, H. & J. Pav6n. 1794. Florae Peruvianae et Chilensis prodromus. Madrid. Scott, A. J. 1979. A revision of Rhodamnia (Myrtaceae). Kew Bulletin 33(3): 429459. BOOK REVIEW The Illustrated Flora of Illinois. Flowering Plants: basswoods to spurges. Robert H. Mohlenbrock. 234 pp. 1982. I S B N 0-8093-1025-2. Southern Illinois University Press, P.O. Box 3697, Carbondale, I L 62901. $22.95 hardbound. This is the tenth volume of the Illustrated Flora of Illinois to be published. The series began in 1967 with the ferns of Illinois. The monocots filled five volumes (Carex still to come) and this is the fourth volume devoted to dicots. Each volume completes a segment of plant families following the system of Robert Thorne. This one contains ten families: Tiliaceae, Sterculiaceae, Malvaceae, Ulmaceae, Moraceae, Urticaceae, R h a m n a c e a e , Elaeagnaceae, Thymelaeaceae and Euphorbiaceae, which consist of 42 genera and 103 species. There are descriptions for all categories of taxa and keys to genera, species, subspecies and varieties. The habitat and geographical range for each species, subspecies and variety is given along with a dot map of Illinois and an illustration of the diagnostic characters. The illustrations were prepared by the a u t h o r ' s son, Mark W. Mohlenbrock.--NOEL H. HOLMGREN, N e w York Botanical Garden.