满江红 man jiang hong

Azolla imbricata (Roxburgh) Nakai; A. imbricata var. prolifera Y. X. Lin; A. imbricata var. sempervirens Y. X. Lin; A. pinnata var. imbricata (Roxburgh) Bonaparte; Salvinia imbricata Roxburgh.

Plants ovate or triangular in outline. Stems slender and creeping, lateral branches axillary, falsely dichotomous, with downward-growing fibrous roots. Fronds as small as sesame seeds, alternate, sessile, imbricate in 2 rows, trapezoidal blade parted into dorsal and ventral lobe; floating dorsal lobes green, or usually becoming purplish after autumn, oblong or ovate, cormous, colorless at margin, densely papillose; submersed ventral lobes ± purplish red, or colorless and transparent, shell-like. Sporocarps in pairs; megasporocarp small, narrowly ovate, apex beaked; megasporangium with 9 floats in 2 rows around it, upper 3 floats larger, lower 6 floats smaller; microsporocarps large, globose or peach-shaped, apex with a short beak, microsporangia long stalked, each containing 64 microspores; microspores individually embedded in 5-8 massulae, massulae with silklike hairs on surfaces.

Floating on ponds, paddy fields, irrigation ditches, widely distributed in the Chang Jiang valley. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Liaoning, Shandong, Shanxi, Sichuan, Taiwan, Yunnan, Zhejiang [Bangladesh, India, Indonesia, Japan, Korea, Malaysia, Myanmar, Pakistan, Philippines, Sri Lanka, C Thailand, Vietnam].

This species has been long cultivated as a fertilizer (upon decomposition) in rice paddies of SE China.

The whole plant is used as green manure and forage; it is used medicinally to induce perspiration, promote diuresis, and to treat a variety of other conditions.

Saunders and Fowler (Bot. J. Linn. Soc. 109: 329-357. 1992) recognized three subspecies within Azolla pinnata: A. pinnata subsp. pinnata, restricted to E and N Australia; A. pinnata subsp. asiatica; and A. pinnata subsp. africana (Desvaux) R. M. K. Saunders & K. Fowler, restricted to Africa and Madagascar. Azolla pinnata subsp. asiatica is separated by the laxer fronds with short, wide submersed lobes (L:B ratio ± 1.2) and the megaspore surface with long prostrate or erect processes. The other subspecies have overlapping fronds with narrower submersed lobes (L:B ratio ± 1.7) and the megaspore surface with generally short tubercles.

Azolla pinnata subsp. asiatica has been divided into three varieties, but these were not accepted by Saunders and Fowler. Their morphological characters and geographic distribution are presented below.

Azolla imbricata var. imbricata: Dorsal lobes of fronds turning from green to reddish from autumn to winter or during hot summertime; plants usually sterile or producing few sporocarps and reproducing vegetatively. Widely distributed in Chang Jiang valley, also in Taiwan [Japan, Korea].

Azolla imbricata var. prolifera Y. X. Lin (Acta Phytotax. Sin. 18: 454. 1980; 多果满江红 duo guo man jiang hong): Plants producing many sporocarps during autumn and dying in winter, reproducing by spores in following year. Henan, Shandong.

Azolla imbricata var. sempervirens Y. X. Lin (Acta Phytotax. Sin. 18: 454. 1980; 常绿满江红 chang lu man jiang hong): Dorsal lobes of fronds evergreen; ventral lobes colorless and transparent, not purplish red. Fujian, Guangdong, Guangxi, Zhejiang [Vietnam].