Marsilea quadrifolia L. is a leptosporangiate aquatic fern which has a played key role in the evolutionary history of plants. It is characterized by heterospory, the ancestral progressive trait that led to the evolution of seeds. The species has creeping, fleshy, adventitious roots containing multiple rhizomes. From the rhizomes a four-leaf clover grows above the water level with a long petiole, at the base of which the sporocarps containing spores are located. Its life cycle is characterized by alternation of generations; reproduction occurs either sexually or by vegetative propagation. The species grows in wet habitats containing shallow water. In the natural environment this includes lakes and small rivers; in agricultural areas it can be found in ditches and rice fields. The species can tolerate nutrient rich waters and because of its phytoremediation properties is capable of partially counteracting the negative effects induced by a moderate organic enrichment of sediments. It has been harvested for centuries in Asian countries as both a food source and for ethnobotanical use in Ayurvedic medicine. Supposed medicinal properties include antibacterial, diuretic, depurative, cytotoxic and antioxidant effects, but these require further investigation and testing.

M. quadrifolia has a widespread distribution, occurring throughout central-southern Europe and extending from Eurasia to tropical and temperate areas of eastern Asia and North America, where it is considered a non-native species. Despite its wide distribution, in its home range the species is threatened with extinction and has already been locally extirpated in several European countries. As a result, it is listed as “Vulnerable” in the European Union Red List due to its scattered distribution and declining population. Habitat loss and degradation, excessive water eutrophication, and agricultural practices such as the use of herbicides, mechanization and simplified rotation are the main threats to the species.

As it is listed in Appendix I of the Bern Convention and in Annexes II and IV of Directive 92/43/EEC as a strictly protected species, in situ and ex situ conservation activities have been conducted in most European countries. Reintroduction, cultivation in botanical gardens and in vitro propagation are the most commonly applied conservation methods.

四叶马西利亚L. 是一种钩孢子囊水生蕨类植物，在植物的进化史上起着关键作用。它的特点是异种孢子，这是导致种子进化的祖先渐进性状。该物种具有包含多个根茎的匍匐、肉质、不定根。四叶草从根茎长出水面以上，有长叶柄，含有孢子的孢子果位于叶柄基部。它的生命周期以世代交替为特征；繁殖通过有性繁殖或无性繁殖进行。该物种生长在含有浅水的潮湿栖息地。在自然环境中，这包括湖泊和小河；在农业地区，它可以在沟渠和稻田中找到。该物种可以耐受营养丰富的水域，并且由于其植物修复特性能够部分抵消沉积物中适度有机富集引起的负面影响。几个世纪以来，它一直在亚洲国家收获，作为食物来源和阿育吠陀医学中的民族植物学用途。假定的药用特性包括抗菌、利尿、净化、细胞毒性和抗氧化作用，但这些需要进一步研究和测试。

M. quadrifolia分布广泛，遍及欧洲中南部，从欧亚大陆延伸到东亚和北美的热带和温带地区，在那里它被认为是非本地物种。尽管分布广泛，但在其栖息地内，该物种面临灭绝的威胁，并且已经在几个欧洲国家局部灭绝。因此，由于分布分散，人口不断减少，它被列入欧盟红色名录中的“易危”。栖息地丧失和退化、水体过度富营养化以及使用除草剂、机械化和简化轮作等农业做法是对该物种的主要威胁。

由于它被列入伯尔尼公约附录 I 和指令 92/43/EEC 的附件 II 和 IV 为严格保护的物种，因此大多数欧洲国家都开展了就地和异地保护活动。重新引入、植物园栽培和体外繁殖是最常用的保护方法。