The Raunkiær system is a system for categorizing plants using life-form categories, devised by Christen C. Raunkiær.
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It was first proposed in a talk to the Danish Botanical Society in 1904 and briefly described in the society's journal Botanisk Tidsskrift.[1][2]
A fuller account appeared in French the following year.[3] Raunkiær elaborated further on the system and published this in Danish in 1907.[4][5]
The original note and the 1907 paper were much later translated to English and published with Raunkiær's collected works.[2][5][6]
Raunkiær's life-form scheme has subsequently been revised and modified by various authors,[7][8] but the main structure has survived.
The subdivisions of the Raunkiær system are based on the place of the plant's growth-point (bud) during seasons with adverse conditions (cold seasons, dry seasons):
Projecting into the air on stems – normally woody perennials - with resting buds more than 25 cms above soil level, e.g. trees and shrubs, but also epiphytes, which Raunkiær separated out as a special group in later versions of the system.
May be further subdivided according to plant height in megaphanerophytes, mesophanerophytes and nanophanerophytes and other characters, such as duration of leaves (evergreen or deciduous), presence of covering bracts on buds, succulence and epiphytism.
Buds on persistent shoots near the ground – woody plants with perennating buds borne close to the ground, no more than 25 cm above the soil surface, (e.g. bilberry and periwinkle).
Buds at or near the soil surface, e.g. daisy, dandelion.
Below ground or under water - with resting buds lying either beneath the surface of the ground as a rhizome, bulb, corm, etc., or a resting bud submerged under water. Cryptophytes are divided into 3 groups:
Annual plants which survive the unfavorable season in the form of seeds and complete their life-cycle during favorable seasons. Annual species are therophytes. Many desert plants are by necessity therophytes.
New addition to the Raunkiaer lifeform classification. Plant that obtains moisture (though not through haustoria) and nutrients from the air and rain; usually grows on other plants but not parasitic on them.[9] This includes some Tillandsia species, as well as staghorn ferns.
Originally placed in Phanerophytes (above) but then separated because of irrelevance of soil position.