Cycas – Morphology, Anatomy and Reproduction

Category	Name
Division	Cycadophyta
Class	Cycadopsida
Order	Cycadales
Family	Cycadaceae
Genus	Cycas

Distribution of Cycas

Cycas is the largest genus within the Old World Cycads and stands out as the most widely distributed genus in the order Cycadales. Its distribution spans across various geographical regions, showcasing its adaptability and ecological significance. Below is a detailed overview of the distribution of Cycas.

• Global Distribution:
  • Cycas is found in numerous countries, including:
    • Japan: Its presence in Japan highlights its adaptability to different climatic conditions.
    • Australia: The Australian habitat provides a unique ecosystem where Cycas thrives.
    • India: A significant portion of its distribution, where it grows naturally in several states.
    • Indochina: The region’s diverse environments support the growth of various Cycas species.
    • China: Cycas contributes to the rich biodiversity of Chinese flora.
    • Mauritius: The island’s unique ecosystem includes Cycas species.
    • Africa: Cycas adapts to different ecological niches across the continent.
    • Nepal: The mountainous terrain of Nepal supports certain Cycas species.
    • Bangladesh: The subtropical climate allows for the growth of Cycas.
    • Sri Lanka: Cycas forms part of the island’s diverse flora.
    • Myanmar: The varied habitats in Myanmar are conducive to Cycas growth.
• Distribution in India:
  • In India, Cycas naturally occurs in several states, including:
    • Orissa: Home to diverse ecosystems, supporting Cycas growth.
    • Assam: The humid climate of Assam is favorable for Cycas.
    • Meghalaya: The mountainous region provides specific niches for Cycas.
    • Tamil Nadu: Cycas species are found in the southern part of India.
    • Karnataka: This state contributes to the diverse habitats of Cycas.
    • Andaman and Nicobar Islands: The islands’ unique biodiversity includes Cycas.
• Species Representation:
  • Cycas is represented by approximately 15 species, though this number can vary according to different classifications:
    • Willis (1966): Reports around 20 species within the genus.
    • Schuster (1932): Recognizes only 8 species, categorizing others as forms, varieties, or sub-species of the main species.
• Notable Species:
  • Among the species of Cycas, certain ones are particularly notable:
    • C. circinalis: Found in the wild in India.
    • C. pectinata: Another species thriving in the Indian subcontinent.
    • C. rumphii: Commonly occurring in the wild.
    • C. beddomei: Found in specific regions.
    • C. revoluta: Widely cultivated in Indian gardens and considered the most common species in cultivation.
    • C. siamensis: Also cultivated in Indian gardens, showcasing its popularity.
• Cultivation:
  • Cycas revoluta is particularly favored for cultivation in Indian gardens, where it is often used for ornamental purposes. This indicates not only its adaptability to cultivation practices but also its aesthetic value in horticulture.

External Morphology of Cycas

The external morphology of Cycas exemplifies its classification as a perennial, slow-growing evergreen plant. Often referred to as a living fossil due to its ancient lineage and the discovery of fossilized specimens like C. fusiana, Cycas resembles a palm tree in appearance. The main plant body is predominantly sporophytic, diploid, and can be distinctly categorized into three primary parts: roots, stem, and leaves. Among the various species, C. media stands out as the tallest, reaching heights of up to 20 feet. Below is a detailed overview of the external morphology of Cycas.

• Roots:
  • Cycas exhibits two types of roots: normal roots and coralloid roots.
    • Normal Roots:
      • These roots penetrate deep into the soil and establish a tap root system.
      • As the plant matures, the normal roots are often replaced by adventitious roots.
      • Their primary functions include anchoring the plant in the soil and facilitating the absorption of water and essential minerals.
    • Coralloid Roots:
      • Arising from the normal roots, coralloid roots develop lateral apogeotropic branches near the soil surface.
      • These lateral roots interact with bacteria, fungi, and algae, leading to their distinctive swollen, knob-like, or coral-like appearance.
      • The presence of these organisms is integral to the roots’ function and structure.
      • Coralloid roots possess minute pores resembling lenticels, which serve a respiratory function, aiding in aeration.
      • Notably, these roots lack root caps and root hairs, differentiating them from typical root structures.
• Stem:
  • The stem of Cycas is characterized by its thickness, erect posture, and woody composition, usually exhibiting an unbranched structure known as a caudex.
    • Branching:
      • Branching is infrequent and typically occurs only as a result of injury or the emergence of adventitious buds.
    • Surface Characteristics:
      • The surface of the stem appears rough due to the presence of persistent woody leaf bases.
      • These leaf bases create a thick protective armor around the stem, which is visually marked by alternating bands of large and small rhomboidal shapes.
      • The larger leaf bases originate from foliage leaves, while the smaller ones come from scaly leaves and megasporophylls in the female plant.
    • Arrangement:
      • The leaf bases are spirally and compactly arranged, culminating in a prominent crown of leaves at the apex of the stem.
• Leaves:
  • Cycas leaves exhibit dimorphism, consisting of two distinct types: scale leaves and foliage leaves, both forming a crown at the top of the stem.
    • Scale Leaves:
      • These leaves are small, dry, and triangular in shape, with a thick covering of brown hairs, known as ramenta.
      • Scale leaves alternate with green foliage leaves, serving the crucial function of protecting the shoot apex and reproductive structures.
    • Foliage Leaves:
      • The foliage leaves also emerge in a crown formation at the apex of the stem.
      • Each foliage leaf is pinnately compound, categorized as unipinnate and paripinnate.
      • A single leaf may contain 80 to 100 pairs of leaflets, which are arranged oppositely or alternately on both sides of the adaxial groove of the rachis.
      • The rachis is spiny below, featuring a sheathing leaf base formed from modified leaflets.
      • Each leaflet is leathery, elongated, ovate, or lanceolate in shape, characterized by an entire margin and acute apex.
      • The pinnae, or leaflets, contain a prominent midrib devoid of lateral veins.
      • The margins of the pinnae are typically flat but can sometimes curve downwards and inwards (revolute), leading to the specific nomenclature of C. revoluta.
      • Young leaves exhibit a unique circinate vernation, displaying coiled leaflets covered in fern-like hairs or ramenta, paralleling characteristics seen in ferns

Internal Structure of Cycas

The internal structure of Cycas, a genus of gymnosperms, exhibits distinct morphological features that serve various physiological functions. Understanding these structures is crucial for comprehending how this ancient plant adapts to its environment. The following overview provides a detailed examination of the internal anatomy of Cycas, focusing on its roots, stem, and leaves.

• Root Structure
  The internal anatomy of Cycas roots can be categorized into normal and coralloid roots, both of which serve vital roles in the plant’s overall function.
  • Normal Root
    • The structure mirrors that of a typical dicot root, featuring a circular outline comprised of several layers:
      • Epiblema: This is the outermost layer, consisting of a single layer of thin-walled cells. Certain cells within this layer differentiate into root hairs, which enhance absorption.
      • Cortex: Surrounding the epiblema is a multilayered zone of thin-walled parenchyma filled with starch. Additionally, this layer contains tannin cells, mucilage cells, and occasionally sphaeraphides (calcium oxalate crystals). The innermost cortex layer, known as the endodermis, is characterized by the presence of Casparian strips, which regulate the movement of water and nutrients.
      • Vascular Tissue: Following the endodermis is the pericycle, which is also multilayered and parenchymatous. The vascular bundles within the root are arranged radially, with xylem exhibiting a diarch and exarch configuration, meaning the protoxylem is positioned toward the outer edge of the root. The protoxylem consists of spiral tracheids, while the metaxylem features scalariform thickenings. Notably, vessels are absent, and the accompanying phloem consists of sieve tubes and phloem parenchyma, but lacks companion cells.
  • Coralloid Root
    • The coralloid roots also share a structure similar to the normal roots but with distinct differences:
      • Epidermis: In younger coralloid roots, the epidermis resembles that of normal roots, while older roots develop a periderm comprising 2 to 5 layers of dead cells.
      • Cortex: The cortex in coralloid roots is broader than in normal roots and features a greenish algal zone located centrally. This zone separates the cortex into outer and inner regions and contains cyanobacteria, such as Anabaena cycadae, which play a crucial role in nitrogen fixation. The endodermis retains its structural similarities to that found in normal roots.
      • Vascular Tissue: Like normal roots, the vascular bundles are present, although in coralloid roots, the xylem is triarch and exarch. Secondary growth is rare or absent, with cork and cork cambium being the only notable secondary structures.
• Comparison of Normal and Coralloid Roots
  The two root types serve different functions and exhibit several key distinctions:
  • Normal Roots: Develop from the radicle and form a tap root system; they are geotropic and primarily function in anchoring and nutrient absorption.
  • Coralloid Roots: Develop from normal roots, are apogeotropic (grow against gravity), have dichotomously branched structures resembling coral, and are involved in nitrogen fixation due to their symbiotic relationship with algae and bacteria.
• Stem Structure
  The transverse section of the Cycas stem shows similarities to that of a dicot stem, characterized by irregular outlines due to persistent leaf bases.
  • Epidermis: This outer layer comprises compactly arranged, thick-walled cells. The presence of persistent leaf bases can cause ruptures in the epidermis.
  • Cortex: The cortex constitutes a significant portion of the stem and consists of parenchymatous cells filled with starch grains, which serve as a source of sago starch. Scattered within the cortex are mucilage canals lined with secretory cells that produce mucilage. The innermost layer, the endodermis, is not distinctly defined.
  • Vascular Cylinder: The vascular cylinder is encased by a less conspicuous pericycle. Similar to dicot stems, it contains conjoint, collateral, open, endarch vascular bundles organized in a ring. The xylem comprises tracheids and parenchyma, with vessels being absent. The phloem consists of sieve tubes and parenchyma without companion cells, and the primary cambium separates xylem from phloem. Medullary rays composed of parenchymatous cells connect the pith to the cortex.
  • Pith: Located centrally, the pith is comprised of parenchymatous cells rich in starch and includes mucilage canals similar to those found in the cortex.
  • Leaf and Girdle Traces: Scattered leaf traces in the cortex represent the vascular supply to the leaves, while girdle traces connect vascular tissue from the main vascular cylinder to the leaves.
  • Secondary Growth: Characterized as a slow process, secondary growth begins with the formation of a cambial ring through interfascicular cambium development. This cambium generates secondary xylem and phloem, leading to a polyxylic and manoxylic wood structure.
• Leaflet Structure
  The leaflet of Cycas is dorsiventral and hypostomatic, distinguished by a swollen midrib and two lateral wings.
  • Epidermis: The outermost layer consists of squarish cells, with a complete upper epidermis and a lower epidermis that features sunken stomata. Both epidermal layers are covered by a thick cuticle.
  • Hypodermis: Beneath the epidermis lies a thick-walled sclerenchymatous hypodermis, which varies in thickness; it helps reduce transpiration and insulates the tissue from excessive heat.
  • Mesophyll: The mesophyll is well-developed, containing differentiated palisade tissue and spongy parenchyma. The palisade layer lies directly beneath the hypodermis, while the spongy parenchyma, found in the wings, consists of loosely arranged oval cells rich in chloroplasts and intercellular air spaces.
  • Vascular Bundle: A single large vascular bundle exists in the midrib, surrounded by a sclerenchymatous bundle sheath. This bundle is conjoint, collateral, open, and diploxylic, with xylem positioned dorsally and phloem ventrally. The xylem and phloem are separated by a non-functional cambial strip.
  • Transfusion Tissue: Comprising tracheidal cells and parenchyma, the primary transfusion tissue facilitates lateral water conduction. The accessory transfusion tissue, located on either side of the midrib, connects with the primary transfusion tissue, compensating for the unbranched midrib and aiding in water transport.

Reproduction in Cycas

Reproduction in Cycas is a fascinating process that encompasses both vegetative and sexual methods. These mechanisms highlight the adaptability of the plant in various environments and its reliance on distinct reproductive strategies.

1. Vegetative Reproduction:
   • The predominant method of vegetative propagation in Cycas occurs through bulbils. These bulbils originate from the axil of scaly leaves and are characterized by their oval shape, featuring a broad base that tapers towards the apex. A bulbil consists of a dormant stem surrounded by several scaly leaves that are arranged in a compact spiral formation.
   • Upon detaching from the parent stem, a bulbil initiates germination by developing numerous roots from its lower side and producing a leaf from the upper side.
   • Importantly, the reproductive nature of Cycas is strictly dioecious, meaning that a bulbil from a male plant will only yield a male plant, while a bulbil from a female plant will exclusively form a female plant.
2. Sexual Reproduction:
   • In Cycas, sexual reproduction is also governed by its dioecious characteristic. Male and female sex organs are produced on separate plants, with sexual maturity typically occurring after several years of vegetative growth, generally in plants over 10 years old.
   • Male plants generate male cones, also known as male strobili, which bear microsporophylls. These cones are terminal, meaning they are located at the apex of the plant.
   • Conversely, female plants develop a loose arrangement of megasporophylls that emerge in succession above the leaves at the upper portion of the stem.

The male reproductive structures in Cycas

The male reproductive structures in Cycas exhibit a remarkable complexity that facilitates the reproductive process in this ancient plant group. Understanding these structures is essential for comprehending the overall reproductive biology of Cycas.

• Male Cone:
  • The male cone, also referred to as the male strobilus, is a large, conical or ovoid structure that is typically solitary, compact, and shortly stalked. It is generally found at the terminal position of the plant and can reach lengths of up to 1.5 meters.
  • Central to the cone is the cone axis, around which several microsporophylls are arranged in tightly spiraled formations. These microsporophylls are perpendicularly attached and facilitate the development of male gametes.
  • At the base of the male cone, numerous young leaves are present. All microsporophylls, with the exception of a few at the base and apex of the cone, are fertile.
  • The emergence of the male cone temporarily halts the terminal growth of the stem since the apical meristem is utilized during its development. Notably, some species of Cycas possess among the largest cones in the plant kingdom.
• Microsporophylls, Microsporangia, and Microspores:
  • Microsporophylls are flat, leaf-like structures that are woody, brown, and characterized by a narrow base and an expanded upper portion, known as the apophysis. Each microsporophyll attaches to the cone axis with a short stalk.
  • The adaxial surface features a ridge-like projection in the middle and an apophysis at the apex. In contrast, the abaxial surface is adorned with thousands of microsporangia arranged in groups of three to five, termed sori. Between these groups, delicate, hair-like structures are present, which are one or two cells in length.
  • Each microsporangium, typically oval or sac-like, is enveloped by five to six layers, including an outer thick epidermis (exothecium), a middle zone of thin-walled cells, and an innermost layer known as the tapetum.
  • The microsporangia house numerous pollen grains or microspores. The expanded region of each microsporophyll contains mucilaginous canals and vascular bundles that facilitate nutrient transport and spore development. A radial line of dehiscence within each sporangium enables the dispersal of microspores.
• Microspore Characteristics:
  • Microsporophylls are typically unbranched; however, some reports indicate abnormal branching. The number of sporangia per sporophyll varies, with species such as Cycas circinalis having an average of 700 and C. media reaching up to 1160 sporangia. A single cone may contain more than 700 million microspores.
  • Each microspore or pollen grain is a rounded, unicellular structure that is uninucleate. It is surrounded by an outer thick exine and an inner thin intine, with the cytoplasm encasing a centrally located nucleus, along with a large vacuole.
  • Scanning electron microscopic studies have revealed that the pollen grains of Cycas revoluta are oblong, featuring a 1-sulcate shrunken aperture and reticulum-like sculpting on the inner layer of the exine, which shares similarities with Ginkgo biloba.
• Development of Microsporangium:
  • The microsporangium develops through a eusporangiate process. Initial hypodermal sporangial cells undergo periclinal division, giving rise to outer primary wall cells and inner primary sporogenous cells. The wall cells divide to form a thick multi-layered wall, while the sporogenous cells proliferate into microspore mother cells.
  • These microspore mother cells subsequently undergo reduction division, resulting in haploid microspores that are arranged tetrahedrally. The tapetum, critical for spore formation, can originate from either the outermost layer of sporogenous tissue or the innermost layer of wall tissue.
  • Importantly, the microspore represents the first cell of the male gametophyte and possesses a haploid chromosome number of 11, although it can sometimes be 12 in C. revoluta. In terms of chromosomal arrangement, female plants are homogametic with an XX-type configuration, while male plants exhibit a heterogametic XY-type chromosome arrangement.

Female Reproductive Organs in Cycas

The female reproductive organs in Cycas are distinct and play a crucial role in the reproductive cycle of this ancient plant lineage. Unlike many flowering plants, Cycas does not produce a true female cone or strobilus; instead, the female reproductive structures manifest as specialized megasporophylls.

• Megasporophylls:
  • The megasporophylls are located around the apex of the monopodial trunk, positioned above each crown of foliage and scaly leaves. They are arranged in a spiral formation, similar to the arrangement of foliage leaves, but in greater abundance, giving the appearance of a rosette.
  • Typically, Cycas produces megasporophylls once a year, arising in an acropetal succession from the apex of the main stem.
  • Each megasporophyll is considered a modification of a foliage leaf and can reach lengths of 30 cm or more, depending on the species. It consists of three distinct regions: an upper dissected or pinnate leafy portion, a middle ovule-bearing portion, and a proximal petiole, which varies in length across different species.
  • The middle ovule-bearing section is broader than the petiole and features ovules arranged in two pinnate rows. The number of ovules ranges from 2 to 12, varying with the species. When young, the ovules appear green, but they mature into fleshy structures that are bright orange or red in color.
  • The upper conical sterile part of the megasporophyll is typically pinnately divided in species such as Cycas revoluta, C. pectinata, and C. siamensis. In contrast, the margins of this upper section are serrate with a tapering acute apex in species like C. beddomei, C. circinalis, and C. rumphii.
  • Notably, Cycas thouarsi possesses the largest ovules among living gymnosperms, measuring about 7 cm in length. The megasporophylls are often covered with yellow or brown hairs, enhancing their visibility.
• Structure of the Ovule:
  • The ovules in Cycas are orthotropous, unitegmic, and shortly-stalked. While typically one ovule fully develops on each megasporophyll, additional unpollinated ovules may remain small and ultimately abort.
  • The outer surface of the ovule can either be smooth, as seen in C. circinalis, or covered with orange-yellow hairs, as in C. revoluta. After fertilization, these hairs are shed, and the ovule transforms into a seed, changing color from orange-yellow to bright red.
  • The ovule features a single, thick integument that encases it except for a micropyle, which serves as an opening. This integument comprises three layers:
    • The outer layer, known as the sarcotesta, is fleshy and can be green or orange.
    • The middle layer, called the sclerotesta, is stony and yellow.
    • The innermost layer is also fleshy, consisting of parenchymatous cells that closely associate with the nucellus.
  • The nucellus extends into a beak-like structure termed the nucellar beak, which protrudes into the micropylar canal. Certain cells at the top of the nucellus dissolve, creating a cavity known as the pollen chamber, where pollen grains are received during pollination.
  • As the seed matures, the nucellus reduces to a thin papery layer that encloses the massive female gametophyte (endosperm). The embryo sac, an enlarged megaspore, resides within the nucellus, and the endosperm forms through repeated divisions of the megaspore nucleus, followed by the formation of free cells.
  • Just below the pollen chamber is the archegonial chamber, which contains 3 to 6 archegonia filled with fluid, essential for fertilization.
• Vascular Supply of the Ovule:
  • Research by Stopes (1904) indicates that out of several vascular bundles in the megasporophyll, only three enter the base of the ovule. The central bundle penetrates the inner fleshy layer of the integument, dividing into branches that extend to the chalazal end of the nucellus without entering it.
  • The two lateral bundles enter the outer fleshy layer and bifurcate, with the outer branch running through the outer layer to the ovule’s apex, while the inner branch penetrates the stony middle layer and extends to the inner fleshy layer, supplying it up to the micropylar end.
• Formation of Megaspores:
  • Within the central region of the nucellus, one cell enlarges and its cytoplasmic contents become dense, representing the megaspore mother cell. This cell undergoes reduction division to produce four haploid megaspores arranged in a linear tetrad.
  • Of these four megaspores, the three positioned towards the micropylar end degenerate, leaving only the lowermost functional megaspore, which serves as the first cell of the female gametophyte.

Economic Importance of Cycas

The significance of Cycas can be outlined as follows:

• Sago Production: The pith of Cycas revoluta is particularly noteworthy for yielding sago, a valuable food source rich in carbohydrates. This sago is obtained by processing the trunk, wherein it is cut into disks, dried, and then pounded into flour. This flour is subsequently mixed with water to allow the starch to settle, producing sago.
• Edible Fruits: The fruits of Cycas revoluta are edible and are known to be rich in protein and soluble non-nitrogenous substances, making them a nutritious food source. Similarly, C. circinnalis produces large fruits that yield a significant quantity of starch annually, adding to the economic viability of these plants.
• Culinary Uses: In South India, the young shoots of C. circinnalis are consumed, showcasing the plant’s role in local diets. Additionally, the seeds and tender fleshy shoots of Cycas pectinata are eaten by hill tribes in Assam, indicating the plant’s cultural and nutritional significance.
• Traditional Practices: The leaves of Cycas revoluta, after undergoing a silvering treatment, are crafted into funeral wreaths in Europe, where they are commonly referred to as ‘palm leaves.’ This highlights the ornamental and ceremonial uses of Cycas foliage.
• Craft and Material Uses: The leaves of C. circinnalis are used in the production of mats in South India, demonstrating the plant’s utility in local craftsmanship and its economic contribution to artisanal practices.
• Medicinal Applications: The fleshy stem of Cycas pectinata is traditionally pounded and utilized as a hair wash to treat diseased root hair, underscoring its role in traditional medicine.
• Caution in Consumption: It is essential to note that while the cooked fruits of Cycas rumphii are consumed by the Andamanese tribes, the uncooked fruits are toxic, indicating the need for careful preparation to avoid poisoning.

Examples of Indian Species of Cycas

Cycas, an essential genus within the cycad family, comprises several species that thrive in diverse ecological conditions across India. Each species exhibits unique morphological characteristics and adaptations suited to their specific habitats. The following outlines some of the prominent species of Cycas found in India, highlighting their key features and distribution.

• Cycas beddomei Dyre:
  • This species is characterized as a small shrub, typically featuring a trunk that reaches approximately 40 cm in height.
  • It is distributed across regions in Andhra Pradesh, Madras, Calicut, and other areas.
  • The leaves of Cycas beddomei are notably large, extending up to 1 meter in length, with a quadrangular rachis.
  • The leaflets are narrow and linear, providing a distinct appearance.
  • Male cones are oblong to ovoid and possess a short peduncle.
  • The megasporophylls are ovate-lanceolate, featuring dentate margins, and are produced during November and December.
• Cycas circinalis Linn:
  • Commonly referred to as ‘Jangli-madan-mast-ka-Phul’ in Hindi and ‘Kamakshi’ in Telugu, this species is predominantly found in the western part of Peninsular India, particularly in the Western Ghats and Orissa Hills.
  • It is frequently cultivated in Indian gardens, indicating its ornamental value.
  • Cycas circinalis is an evergreen tree with leaves measuring between 1.5 to 3 meters in length, consisting of about 100 pairs of leaflets.
  • The leaflets are linear-lanceolate with flat margins and an acuminate apex.
  • Male cones are cylindrical to ovoid, accompanied by a short peduncle.
  • The upper sterile part of the megasporophyll is longer than it is broad and features dentate margins, while the megasporophylls contain brown tomentose hairs.
• Cycas pectinata Griff:
  • This species is distributed in regions such as Sikkim, Assam, Manipur, and the Someshwar Hills of Bihar, as well as neighboring countries like Nepal and Bangladesh.
  • Its trunk can reach a length of 1.5 to 2.5 meters, displaying a robust structure.
  • The leaves attain a length of approximately 1.5 to 2 meters, with leaflets that are narrow and linear, tapering into a minute spine, measuring between 14 to 25 cm in length.
  • The male cone is cylindrical-ovoid, and the upper part of the megasporophyll is as broad as it is long.
• Cycas revoluta Thunb:
  • Cycas revoluta is native to Japan, China, and Taiwan, but it is extensively cultivated in various parts of the world, including India.
  • This species derives its name from the revoluted margins of its leaflets, contributing to its distinctive appearance.
  • It resembles a palm-like tree, with a trunk that can reach up to 2 meters in height.
  • Male cones are typically cylindrical or ovoid-oblong.
  • The megasporophylls range from 10 to 25 cm in length and are densely tomentose, showcasing their protective adaptations.
• Cycas Rumphii Miq:
  • This evergreen palm-like tree is primarily distributed in the Andaman and Nicobar Islands of India, as well as in Sri Lanka, Malaysia, and Australia.
  • Its trunk can attain a height of up to 4 meters, signifying its robust nature.
  • The leaves range in length from 1 to 2 meters and contain between 50 to 100 or more pairs of leaflets.
  • The male cone is shortly stalked and exhibits an ellipsoidal to oblong shape.
  • The megasporophylls are ovate-lanceolate, featuring many small teeth.
• Cycas siamensis Miq:
  • Found in regions including Myanmar, Thailand, China, and Laos, Cycas siamensis is characterized as a palm-like tree.
  • The leaves of this species can reach about 1 meter in length, contributing to its stature.
  • Leaflets are narrow and linear, typically ending in a mucronate or acuminate apex.
  • The male cone is ovoid-oblong in shape, signifying its reproductive structure.
  • The sterile blade of the megasporophyll is as broad as it is long, and it usually contains only 2 ovules.
  • Notably, Burkill (1933) considered Cycas siamensis a geographical form of C. pectinata, while Pant and Nautial (1963) also recognized similarities between the two species based on epidermal and anatomical studies.