Retrophyllum

Retrophyllum
Retrophyllum rospigliosii
Scientific classification
Kingdom:	Plantae
Division:	Pinophyta
Class:	Pinopsida
Order:	Pinales
Family:	Podocarpaceae
Genus:	Retrophyllum C.N.Page
Type species
Retrophyllum vitiense (B.C. Seemann) C.N. Page

Retrophyllum is a genus of conifers in the family Podocarpaceae. It contains five generally recognized species with a disjunct distribution in the Southern Hemisphere, found in Papuasia and also in South America.Retrophyllum are evergreen trees typically occurring in tropical rainforests and cloud forests.

The name Retrophyllum is derived from the Latin retro, meaning "backward" or "reversed", and the Greek phyllos, meaning "leaf". The name refers to the unique phyllotaxis where the adaxial surfaces of the leaves face up on one side of the shoot and down on the other.

Retrophyllum are evergreen trees. They range in size from dwarfed to very large, reaching heights in excess of 40 and potentially 60 meters.Resin canals are found in both leaves and the seed cones. The bark is usually smooth at first, becoming fissured or flaking with age.

The leaves are generally flat with a decurrent base and a spreading blade, but leading and cone-bearing shoots may also have small appressed scale-like leaves.The base phyllotaxis or leaf arrangement is spiral though the leaves usually form subopposite and nearly decussate pairs. The leaves of a lateral shoot are further twisted at their petioles to form two pectinate rows in a horizontal plane around the shoot. The leaf petioles in Retrophyllum are uniquely twisted on the lateral shoots in opposite directions on each side of a shoot orienting the leaf blades with the adaxial or ventral surface upwards on one side of the shoot and the abaxial or dorsal surface upwards on the opposite side of the shoot. The leaf blade varies in shape from lanceolate to narrowly ovate. The leaves have conspicuous midribs and are amphistomatic with stomata present on both sides.

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Wikipedia