Dr. Suranjana Sarkar Assistant Professor in Botany Surendranath College, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata

naked

Four major living groups.

Cycads (Cycadophyta),

Welwitschia group (Gnetophyta),

Ginkgo, the Maiden Hair Tree (Ginkgophyta), and the conifers (Pinophyta) . Dr. Suranjana Sarkar, SNC, Kolkata Found in the Jurassic period of the Mesozoic era. (250-145 million years ago)

They can grow in Subtropical and Tropical climates.

They grow in any type of soil; mostly moist habitats.

185 different of Dr. Suranjana Sarkar, SNC, Kolkata bougainvilleana Cycads

Cycads resemble palms or tree-ferns in overall appearance but differ greatly in detailed structure and reproductive behaviour. Cycads are dioecious (i.e. male and female reproductive structures are borne on separate ), and reproduction is by produced on open carpophylls or seed- bearing leaves. Although technically woody plants, unlike other woody plants, cycads have a thick, soft stem or trunk made up of mostly storage tissue with very little true wood. The living cycads include about 250 species, with 11 genera in 3 families.

Microcycas calocoma Photo Dennis Stevenson Dr. Suranjana Sarkar, SNC, Kolkata Female coneCuban species Dr. Suranjana Sarkar, SNC, Kolkata In India Cycas is represented by six species— C. revoluta, C. pectinata, C. siamensis, C. beddomei, C. rumphiand C. circinalis.

Cycas revoluta is the most commonly cultivated species of Indian gardens. It also occurs in China, Africa, Nepal, Sri Lanka and Japan. Its natural habitat is in open, sunny, well-drained situations. It is a palm-like tree with size varies from 1-2 meters. As it yields ‘’, from the mucilage in its main trunk. It is popularly called ‘sago palm’. Leaflets are 6-8 mm broad with revolute margins.

Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Sporophytic Body

• Plants are low and palm-like, height 4-8 feet • Tallest species, C. media – upto 20 feet high • Root - Tap root system. Coralloid roots or corallorhiza formed from some apo-geotropic roots which are inhabited by cycadacearum a blue green alga • Stem unbranched, columnar and covered with persistent leaf bases • Leaf segment remains circinnatelyinvolute within the bud – leaves dimorphic, small brown scale leaves and large pinnately compound foliage leaves. • Female reproductive structures – the megasporophylls are not aggregated in cones • Ovules (2 or more) borne on the lower margins in ascending order Dr. Suranjana Sarkar, SNC, Kolkata Root External morphology

Dr. Suranjana Sarkar, SNC, Kolkata Cycas: Coralloid root

Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Stem

Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Anatomy of stem The stem anatomy of Cycas is simple and shows some primitive features. It shows the following tissues:- 1. Epidermis 2. Cortex 3. Endodermis, Pericycle and Vascular Cylinder 4. Medullary rays 5. Pith

Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Leaf

Dr. Suranjana Sarkar, SNC, Kolkata Young leaves have circinate vernation like those of ferns and always covered with brown hairs called ramenta

Circinate vernation is a term that describes the tightly coiled manner in which a fern frond emerges where the tender growing tip of the frond is protected within a coil. This type of vernation is also seen in Cycas, the only genus that is recognized in the family Cycadaceae where the leaves grow directly from the trunk. The pinnately compound leaves grow in a rosette form, with new foliage emerging from the top and center of the crown. Circinate vernation is found in these new leaflets. Cycas-Circinate vernation of young foliage leaf

Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Dr. Suranjana Sarkar, SNC, Kolkata Thank You…

Stay indoors, stay safe.

Dr. Suranjana Sarkar, SNC, Kolkata