Callitriche platycarpa

Description (after Lansdown 2008): — Stem and leaf scales present. Leaf bases connate. Lingulate leaves ± parallelsided or tapering from base, often sinuous, 10.4 – 28.5 mm long × 0.1 – 2. mm wide; expanded submerged or floating leaves elongate-spathulate to elliptic, 11.1 – 15.9 mm long × 2 – 3.8 mm wide, 3 - veined often with one or two short processes arising from the secondary veins; petiole (0.3 –) 1.1 – 5.5 mm long; the apical leaves forming a floating rosette; leaves of terrestrial plants 1.5 – 3.8 mm long × 0.5 – 1.8 (– 2.3) mm wide, narrowly elliptic. Flowers solitary. Bracts translucent, appearing whitish, falcate, persistent 0.3 – 2.6 mm long. Styles erect and slightly curved, 0.5 – 6.5 (– 7.8) mm long. Filament initially erect, ultimately recurved ≤ 8.3 mm long; anthers (0.5 –) 0.6 – 0.8 mm long × 0.6 – 1 mm wide, quadrilocular; pollen yellow. Fruit not strumose, subsessile, ± as wide as high, pale brown when mature, 1.3 – 1.7 mm long × 1.4 – 1.8 mm wide, narrowly winged throughout. Illustrations: — Figures on pages 114 – 115 in Lansdown 2008. Fig. 10 h. Recognition: — C. platycarpa can be distinguished from other Callitriche species in the region except C. stagnalis by the large, winged, pale brownish-grey fruit. It can only reliably be distinguished from C. stagnalis by the pollen of which most in each anther is bluntly triangular, as opposed to ellipsoid in C. stagnalis. C. platycarpa often produces linear, submerged leaves which are very rare in C. stagnalis, while the fruit of C. platycarpa are typically more narrowly-winged than in C. stagnalis and more greyish, but these characters are not diagnostic.

standing waters

shortlived

eutrophic

aquatic

cuddly

mobile

Distribution: — Non-native. Within the region. Callitriche platycarpa has been reported from a single site in New Zealand. In its native range it is mainly found in western Europe. It occurs throughout Britain and Ireland and throughout France, extending north into southern Sweden and east to the Czech Republic. Habitats and Ecology: — There is no information on the habitat in which it was reported from New Zealand. In its native range Callitriche platycarpa typically occurs in lowland ditches, canals, streams, ponds and river backwaters. 0 – 520 m elevation in its native range, Palmerston North is at around 50 m elevation. Conservation Status: — Least Concern (LC) (Lansdown 2011). Notes: — Within the region Callitriche platycarpa is represented by three specimens in CHR determined as this species by R. Mason, two of which represent material cultivated from the first gathering which was collected from North Island, Palmerston North, October 1973, Forde, M. B. s. n. (CHR 279611, cultivated material CHR 279607 A, CHR 279607 B). Given the frequent problems with mis-identification of unfamiliar Callitriche species, even by specialists, this material needs to be confirmed by microscopic examination of pollen which is unique within the genus being tetrahedroid and appearing bluntly triangular in outline (Lansdown 2008: 115, Fig. I 1).