Species of the genus Saxicolella Engl. (Podostemaceae) are African rheophytes, restricted to rapids and waterfalls as are all members of the family. Previously, Saxicolella sensu lato was shown to be polyphyletic with two separate clades. The name Pohliella Engl. was recently resurrected for one clade that is sister to the American genera Ceratolacis (Tul.) Wedd., Podostemum Michx. and all Old World Podostemoideae. Pohliella has distichous phyllotaxy, bilocular ovaries, filiform roots with paired holdfasts, and rootcaps. The second clade, Saxicolella sensu stricto, including the type of the generic name, has spiral phyllotaxy, unilocular ovaries, ribbon-like or crustose roots that lack both holdfasts and rootcaps. Saxicolella sensu stricto, sampled from the type species, S. nana Engl. of Cameroon, is embedded within and near the base of the major clade of African podostemoids and is sister to all other African genera apart from Inversodicraea R.E.Fr. and Monandriella Engl. Recently reduced to three species in Cameroon and SE Nigeria by the resurrection of Pohliella, Saxicolella sensu stricto is expanded to eight species in this monograph by description of five new taxa. Saxicolella futa Cheek and S. deniseae Cheek are newly described from Guinea, S. ijim Cheek from Cameroon, the informally named S. sp. A from Gabon, and S. angola Cheek from Angola. The known geographic range of the genus is thus expanded c. 2,500 km westwards to Guinea from eastern Nigeria and c.1,500 km southeastwards from near Yaoundé to Cuanza do Sul, Angola. The greatest concentration of species occurs in the Cross-Sanaga interval of western Cameroon and eastern Nigeria, with three species. Cameroon (3 species) followed by Nigeria and Guinea (2 species each) are the countries with highest species diversity. A classification is proposed grouping the species into three subgenera (Saxicolella, Butumia (G.Taylor) Cheek comb. et stat. nov. and Kinkonia Cheek subgen. nov.) based on root morphology and shoot position and morphology. The discovery, morphology, circumscription, distribution and ecology of Saxicolella is reviewed, an identification key to the species is presented, together with descriptions, synonymy and links to illustrations. All of the species are provisionally assessed as either Endangered or Critically Endangered using the IUCN 2012 Red List Criteria. The major threats, above all, are hydro-electric projects. Saxicolella deniseae may already be globally extinct, and two of the four known locations of S. angola appear lost, S. sp. A of Gabon is threatened at at least one of its three locations, while S. futa is threatened at all three locations. Contamination of watercourses by increased turbidity from silt-load due to anthropic changes and by eutrophication from pollution are also threats for the majority of the species.

Saxicolella Engl属的物种。（Podostemaceae）是非洲流变植物，仅限于急流和瀑布，就像该科的所有成员一样。以前，Saxicolella sensu lato被证明是多系的，具有两个独立的进化枝。Pohliella Engl的名字。最近复活的一个进化枝是美国Ceratolacis (Tul.) Wedd., Podostemum Michx 属的姐妹。和所有旧大陆 Podostemoideae。Pohliella具有双列叶序、双眼卵巢、丝状根和成对的固着物和根冠。第二个进化枝，Saxicolella sensu stricto，包括属名的类型，具有螺旋叶序、单房子房、带状或硬壳状根，缺乏固着物和根冠。Saxicolella sensu stricto，取自模式种S. nana Engl。喀麦隆的，嵌入在非洲足蚌类主要进化枝的基部内和附近，是除Inversodicraea REFr 之外的所有其他非洲属的姐妹。和Monandriella Engl。最近由于 Pohliella 的复活，喀麦隆和尼日利亚东南部减少到三个物种，在本专着中通过对五个新分类群的描述，将 Saxicolella sensu stricto扩展到八个物种。Saxicolella futa Cheek 和S. deniseae来自几内亚的新描述的脸颊，来自喀​​麦隆的S. ijim Cheek，非正式地命名为S. sp。A 来自加蓬，S. angola Cheek 来自安哥拉。因此，该属的已知地理范围扩大了c。从尼日利亚东部向西至几内亚 2,500 公里，从雅温得附近至安哥拉南宽扎向东南约 1,500 公里。物种最集中的地方是喀麦隆西部和尼日利亚东部的 Cross-Sanaga 区间，共有三个物种。喀麦隆（3 种）其次是尼日利亚和几内亚（各 2 种）是物种多样性最高的国家。提出了一个分类，将物种分为三个亚属（Saxicolella、Butumia (G.Taylor) Cheek comb. et stat. nov. 和Kinkonia脸颊亚根。nov.) 基于根形态和枝条位置和形态。回顾了Saxicolella的发现、形态、界限、分布和生态学，介绍了该物种的识别关键，以及描述、同义词和插图链接。使用 IUCN 2012 红色名录标准，所有物种都被临时评估为濒危或极度濒危。首先，主要威胁是水电项目。Saxicolella deniseae可能已经在全球范围内灭绝，S. angola的四个已知位置中的两个似乎丢失了，S. sp。加蓬的 A 在其三个地点中的至少一个受到威胁，而S. futa在所有三个地点都受到威胁。由于人为变化引起的淤泥负荷增加的浊度和污染引起的富营养化对水道的污染也是对大多数物种的威胁。