Gymnospermous Wood

* Monoxylic wood: The wood formed may be in one ring due to persistent cambium. Such a wood is called as monoxylic e.g, Pinus.

Cambial activity is short lived, cortex and pith are broad, parenchymatous rays are broad, wood is soft and commercially useless. e.g., Cycas.

* Pycnoxylic wood: The wood is formed in more than one ring due to ephimeral nature of cambium. Such a wood is called as polyxylic. Cambial activity is long lived, cortex and pith are reduced, parenchymatous rays are few, wood is hard and compact, wood is commercially most important and used as good quality timber. e.g., Pinus.

* The wood of Cedrus deodara is used for making railway sleepers. It is also used as a structural timber and making bridges. The wood of Callitris verrucosa, Pinus roxburghii, P. wallichiana, P. pinaster, P. lambertiana etc. is used for making furniture. Juniperus virginiana wood is used for making pencils. The gymnosperm Agathis australis is perhaps the largest timber producing tree of the world.

Pinus:

* Pinus is an evergreen, perennial plant of xerophytic nature. Mostly the species are tall and straight. The whorled branching gives a typical conical or ex-current appearance to the plant (due to apical dominance). The plant body is sporophyte and the plants ate monoecious. The plant body is differentiated into roots, stem and leaves.

Fig: Pinus

* Pinus reproduces only by means of spores. Unlike Cycas, here the, micro and megasporophylls form compact male and female cone or strobilus respectively.

* Pinus plant is sporophyte (2x), heterosporous /(producing two type of spores - microspore and megaspore), monoecious (male and female cones are borne on same plant) and autoecious (male and female cones are borne on .different branches).

Cycas:

* Cycas is an evergreen palm-like plant. It is the only genus of family Cycadaceae represented in India.

Fig:Cycas

* Cycas plants are dioecious and reproduce by following methods:

(1) Vegetative propagation: It occurs by means of bulbils (resting adventitious buds) which are produced on the stem in the axil of scale leaves. They break up from the parent plant and germinate to give rise to new plant.

(2) Sexual reproduction: Plant of Cycas is sporophyte (2n) and dioecious. The sexual reproduction is of oogamous type, i.e., takes place by the fusion of distinct male and female gametes.

The male and female gametes are formed by the germination of micro and megaspores which are born on microsporophylls and megasporophylls. The microsporophylls are grouped together to form a compact conical structure called male cone, whereas the megasporophylls are not aggregated to form a cone, they are produced at the apex of the stem in succession with the leaves.

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