Morphological Nature of Floral Cup in Lauraceae

l~Yoc. Indian Acad. Sci., Vol. 88 B, Part iI, Number 4, July 1979, pp. 277-281, @ printed in India.

Morphological nature of floral cup in Lauraceae

S PAL School of Plant Morphology, Meerut College, Meerut 250 001

MS received 19 June 1978

Abstract. On the basis of anatomical criteria the floral cup of Lauraceae can be regarded as appendicular, as the traces entering into the floral cup are morphologi- cally compound, differentiated into tepal and stamen traces at higher levels. The ontogenetic studies also support this contention. The term Perigynous hypanthium is retained for the floral cup of Lauraceae as it is formed as a result of intercalary growth occurring underneath the region of perianth and androecium.

Keywords. Lauraceae; floral cup; morphological nature; appendicular; perigynous hypanthium.

1. Introduction The family Lauraceae has received comparatively little attention from earlier workers because of difficulty in procuring the material. So far very little work has been done on the floral anatomy of this family (Reece 1939 ; Sastri 1952 ; Pal 1974). There has been considerable difference of opinion regarding the nature of floral cup in angiosperms. The present work was initiated to study the morphological nature of the floral cup.

2. Materials and methods

The present investigation embodies the results of observations on 21 species of the Lauraceae. The material of Machilus duthiei King ex Hook.f., M. odoratissima Nees, Persea gratissima Gaertn.f., Phoebe cooperiana Kanjilal and Das, P. goal- parensis Hutch., P. hainesiana Brandis, Alseodaphne keenanii Gamble, A. owdeni Parker, Cinnamomum camphora Nees and Eberm, C. cecidodaphne Meissn., C. tamala Nees and Eberm, C. zeylanicum Noes, Litsea polyantha Juss, Crypto- carya amygdalina Nees, C. floribunda Nees, was collected from the plants growing in the Forest Research Institute, Dehra Dun, and that of Cinnamomum officinarum Nees, Neolitsea sericea BI., Apollonias barbujana (Cav.) R.Br., Cryptocarya abovata R.Br., C. woodii R.Br., from the Royal Botanic Gardens, Sydney, Australia. Flowers of Cassytha filiformis Linn. were obtained from Jaipur through the 277

P.(B)--3 278 S Pal cot~rtesy of Professor B Tyagi. Following customary methods ol~ dehydration and embedding the sections were cut at 6-12/z and stained with safranin-fast- green and crystal violet erythrosin combinations.

3. Observations and conclusions

The flower of Lauraceae is perigynous and has a cup-like stiucture around the base of ovary or around the ovary, on which the outer floral parts are inserted. The floral cap is short in majority of taxa, however it may be long and ovoid or campanulate (Litsea polyantha) or long and tubular (Cryptocarya). The cup either surrounds the base of ovary (Apollonias, Machilus, Persea, Phoebe) or extends upto the middle of ovary (Alseodaphne, Cassytha) or upto 3/4th length of the ovary (Onnamomum, Litsea, Neolitsea) or almost upto the top of the ovary ( Cryptocarya). The floral cup in all the species investigated shows a somewhat uniform anatomical pattern. It is generally traversed by six strands which are conjoint perianth- stamen traces, they branch tangentially into three series of six traces each at different levels in various taxa. The outer series form the medians of the perianth segments of both the whorls, the second series supplies to the first and second whorls of stamens and the third series constitutes the vascular supply of the stamens of the third whorl and of the staminodes (fourth whorl of stamens). ~lhus a tepal trace and two stamen traces lie upon the same radius. However in Cryptc- carya the traces for tepals and stamens remain differentiated right from the base of the receptacle. Similar cup-like structures occur in a number of other families and they have been variously interpreted. The floral cup has been interpreted as receptacular in Calycanthaceae (Smith 1928), Santalaceae (Smith and Smith 1942 a, b), Cactaceae (Sharma 1949, Tiagi 1955), etc. whereas it has been regarded as appendicular in Ro~aceae (Sau,nders 1925; Jackson 1934), Lagerstraemia and Ammania (Saunders 1936), Kalanchoideae (Tilson 1940); Saxifragaceae (Palmatier 1943), Lythrum and Epilobium (Bonner 1948), Turneraceae (Rao 1949), Thymeliaceae (Heinig 1951) and Stellaria glauca (Pal and Murty 1978). The floral cup of Moringaceae and Passifloraceae has been considered as partly axial and partly appendicular (Puff 1942, 1947). All the above workers have considered the course of vascular bundles as the guiding factor in determining the morphological nature of floral cup. Where recurrent bundles are observed the floral cup has been regarded as receptacular, while in their absence it has been considered as appendicular. On the basis of the present anatomical study the floral cup of Lauraceae can be regarded as appendioular since the traces entering into the floral cup are morpho- logically compound and they differentiate into tepal and stamen traces at a higher level. The ontogenetic studies also support such a contention. Distinct primordia for all floral appendages are formed. However, daring their early onto- geny, due to interprimordial growth, the members of each perianth whorl become coherent to each other. Intercalary growth of common basis of outer and inner whorl of tepal primordia as well as the bases of stamen primordia result ih the formation of a cup around the base of ovary. The extent of intercalary growth Morphology of floral cup in Lauraceae 279 determines the size of floral cup (figures 1-8). On anatomical and ontogenetic grounds Kasapligil (1951) also considered the floral cup in Umbellularia as appendicular. Recently, Leins (1972) discussed the nature of inferior ovary in terms of intercalary growth. He asserted that floral cup is formed by intercalary growth in the tissues underneath the primordia of androecium and perianth. Various terms have been applied by different authors to designate the floral cup in the flowers of angiosperms. It has been referred to as a hollow receptacle (Baillon 1880; Rendle 1938), as a calyx tube (Lindley 1853 ; Le Maout and Decaisne 1876 ; Hooker 1879 ; Koehne 1903 ; Bailey 1949 ; Fernald 1950 ; Gunderson 1950 ; Jepson 1951; Hutchinson 1959),as hypanthium (Lawrence 1951; Gleason 1952), as androperianth (Core 1955) and as floral cup or floral tube (Jackson 1934; Tilson 1940; Kasapligil 1951; Parkin 1955). Recently, Leins etal (1972) and Pal and Marty (1978) used the term Perigynous hypanthium for the product formed as a result of intercalary growth occurring underneath the region of porianth and androecium.

Figures 1-8. 1-4. Diagrammatic representation (in longitudinal section) of the extent of formation of floral cup and course of vascular bundles. 1. Persea gratissima. 2. Alseodaphne keenaniL 3. Cinnamomum zeylanicum. 4. Cryptocarya amygdalina. 5-8. Diagrammatic representation of floral apices (in longitudinal section) after the formation of tepal and stamen primordia. The parallel lines below the tepal and stamen primordia indicate the extent of intercalary growth. 5. Persea gratissima. 6. Alseodaphne keenanii. 7. Cinnamomum zeylanicum. 8. Cryptoearya amygdalina. (O--Ovary; P--Tepal or tepal primordium of outer perianth whorl; P1--Tepal or tepal primordium of inner perianth whorl; S1--Stamen or stamen primordium of first whorl; S2--Stamen or stamen primordium of second whorl; Ss-- Stamen or stamen primordium of third whorl; S4--Stamen or stamen primordium of fourth whorl; Ss-----Stamenor stamen primordium of fifth whorl; S6--Stamen or stamen primordium of sixth whorl.) 280 S Pal The term hollow receptacle indicates the receptaculax nature of floral cup. The term calyx tube is also confusing as petals and stamens are never formed on the calyx. It is opined that the floral cup of Lauraceae be called the Perigynous hypanthium as it is formed by intercalary growth in the tissues underneath the primordia of perianth and androecium.

Acknowledgements The author thanks Profs V Puri, Y S Murty and Dr V Singh for their sugges- tions and help. He is also thankful to the authorities of UGC, New Delhi, for financial assistance.

References

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