(1) Most plants are perennial and woody
(2) They are xerophytic, with sunken stomata and thick cuticle.
(3) The xylem is without vessels and phloem lacks companion cells.
(4) Reproductive organs are usually in the form of cones or strobili. The male cones are made up of microsporophylls and female cones are made up megasporophylls. .
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(5) Microsporophylls bear microsporangia (900- 1000 microsporangia in sori in cycas and two microsporangia in Pinus sps.)
(6) Large number of microspores (pollen grains) are produced in microsporangia, after reduction division, which later form male gametophytes.
(7) Male gametophytes of all gymnosperms produces pollen tubes.
(8) In the nucellus of megasporangia (ovules) one of the cells forms megaspore mother cell which after reduction division forms a linear tetrad of megaspores of which only one is functional.
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(9) Functional megaspore forms female gametophyte (also called endosperm). Thus, the endosperm is a pre-fertilization tissue in gymnosperms.
(10) On the micropylar end of female gametophyte are differentiated in two or more archegonia.
(11) All gymnosperms are wind pollinated.
(12) Usually polyembryony is found in seed although ultimately only one embryo survives.
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(13) Archegonia lacks neck canal cells.
(14) Embryo bears two as in Cycas or more (10- 11 in Pinus) cotyledons.
(15) All gymnosperms are woody and perennial, some of these are very large live for thousands of years e.g. Sequoia sempervirens.