Cycadaceae (Cycads) family is a dioecious (male and female reproductive structures on different plants), palm-like tree that can grow up to 12 m tall. The family is represented by a single genus known as Cycas. Currently, there are 120 accepted species (The World List of Cycads, 2021) with 4 of them recorded in Peninsular Malaysia i.e, Cycas cantafolia (locally known as Paku lagu and Paku Mas in Temuan tribe), Cycas clivicola, Cycas edentata (Paku Laut in Malay) and Cycas macrocarpa (Bogak in Malay) (Jutta, 2012).
The epithet for the species clivicola is derived from the Latin words 'clivis' meaning a cliff and 'cola' meaning a dweller as this plant usually grows on cliffs. In 1999, K.D. Hill described Cycas clivicola to two subspecies namely C.clivicola subsp. clivicola and subsp. lutea.
C. clivicola subsp. clivicola is known as Paku Aji in Malay. This subspecies is distributed in Southern Thailand and Peninsular Malaysia especially in Kedah, Perlis and Perak. It is restricted to inland and offshore limestone, usually on cliffs, where it directly grows on a rock or wedged into crevices and cracks (Jutta, 2012; Yong et al., 2021).
This tree can grow up to 7 m in height with a prostrate-pendulous to pendulous stem with 60 cm in diameter at the base where it is conspicuously enlarged and bulbous. The bark is light grey with a honeycomb-like pattern, smooth and becomes deeply fissured as it ages. It can produce up to 50 or more leaves per tree. The young leaves are covered with woolly, pale yellow hairs that are shed eventually as the leaves uncurl. Each leaf has about 20-60 cm long petiole, 40-140 cm long rachis and 30-100 pairs of linear-shaped pinnae. The pinnae are stiffly coriaceous (resembling the texture of leather), shiny to glaucous green above (especially in younger leaves) and paler beneath. The pinnae also have flat margins with notable midribs above and below (Jutta, 2012).
The cycads family is known to produce the largest sperm and ovules in the plant kingdom. Male plants produce male cones while the females produce female cones consisting of leafy-like structures called megasporophylls. The megasporophylls are not organised into true cones; instead they are arranged spirally in a loose or dense grouping around the stem apex.
A male cone of C. clivicola subsp. clivicola is pale yellow, ellipsoid (measuring about 68 cm long with 17.5 cm in diameter) and shortly stalked. The male cone consists of many spathulate, pale yellow microsporophylls containing closely arranged pollen sacs (microsporangia) that cover about three-quarters of the surface. Meanwhile, the female cone forms a closed-type cone where the individual megasporophylls remain erect and form a tight overlapping structure similar to a cabbage-like head. The cone is covered with soft, yellow-brown silky hair throughout and each megasporophyll carries 1-4 ovules (Jutta, 2012).
Cycads are generally traded as ornamental plants, resulting in decreasing wild populations of some species, i.e. Cycas edentata and Cycas clivicola subsp. clivicola. In the Malaysia Red List, C. clivicola subsp. clivicola is considered as Endangered (Yong et al., 2021) due to overharvesting for commercial trading as an ornamental plant (Jutta, 2012). However, the species is globally listed as Least Concern by the IUCN Red List of Threatened Species (Hill, 2010).
