2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 | 2014 | 2013

Questions and Answers: 2015

Question: Trying to differentiate Persicaria hydropiperoides and setacea on Martha's Vineyard. Flora Novae Angliae uses differences in enlargement of ocreal hairs …

• Question

  Trying to differentiate Persicaria hydropiperoides and setacea on Martha's Vineyard. Flora Novae Angliae uses differences in enlargement of ocreal hairs at base to distinguish. Photos of ocreae by Andrew Nelson and Arieh Tal on GoBotany show no enlargement that I can see. What am I misinterpreting? What other clues can I use?

  Answer

  Dear gregorypalermo, the images on Go Botany do show the features, but they are not enlarged enough for you to discern what is going on without knowing what to look for. To identify these species, you need magnification so you can measure carefully the hairs on the stipule surface and determine the length that is fused to the surface divided by the total length of the hair. In brief, Persicaria setacea has hairs on the stipule surface that are fused only a short distance at the base (vs. P. hydropiperoides, with hairs fused to the stipule much more of their total length), in effect making the stipule of P. setacea look more bristly. The hairs I am discussing are not those at the top margin of the stipule, but those on the surface of the tubular stipule. Feel free to continue this discussion at ahaines[at]newenglandwild.org if I can help you further.