Discussion
The degree of variation in morphology, the structure of the trichomes and fruits, and the kinds of hair are important characteristics in the taxonomy of angiosperms. Drude (1898), Heywood and Dakshni (1971), Nasir (1972), Arora (1976) and Pimenov et al. (2019) have all investigated these characteristics, including the stylopodium, the number of sectretory ducts in the mericarps, and the main and secondary valleculae vittae. Micromorphological research has revealed that Psammogetonspecies differ noticeably from one another. When Rechinger awarded the designation of holotype to the specimens kept in the herbarium W, he established that Wagenitz’s identification of Psammogeton canescens (DC.) Vatke subsp. cabulicus Wagenitz was accurate (1982). The type specimens were gathered in Bagrami, which is close to Kabul. In 1980, Nasir changed the name of this subspecies toPsammogeton cabulicus (Wagenitz) Nasir, giving it the status of a species. In my opinion, Psammogeton cabulicus described by Nasir is strikingly dissimilar from the Psammogeton canescens subsp.cabulicus Wagenitz described earlier. There is either error in keeping P. canescens subsp. cabulicus as synonym underP. cabulicus (Wagenitz) Nasir as confirmed through the specimens undertaken to study by authors. Perhaps this is the main reason that these taxa remained unresolved so long without knowing the current status of these taxa and data available related to these taxa being insufficient. The identity of the species P. cabulicus(Wagenitz) is in fact different, therefore combination as given by Nasir misidentified, therefore unacceptable. Furthermore, the illustration of these two taxa are so different from each other that these cannot be treated as same. The authors urge that holotype of P. canescenssubsp. cabulicus should not be placed under synonym underP. cabulicus (Wagenitz) Nasir since P. canescens subsp.cabulicus is quite distinct supported by taxonomic characters.