Callitriche palustris var. palustris

Lansdown, Richard V., 2022, The genus Callitriche (Plantaginaceae, Callitricheae) in Australasia and Oceania, Phytotaxa 547 (3), pp. 243-284 : 265

14a. Callitriche palustris var. palustris

Description (after Lansdown 2008):—Stem and leaf scales present. Leaf bases connate. Lingulate leaves linear to narrowly expanded, 5.6–9.7 mm long × 0.5–1.2 mm wide; expanded submerged or floating leaves elliptic to more or less orbicular, 3.6–9.9(–10.3) mm long × 1.2–4.3(–4.5) mm wide, most leaves have at least part of a tertiary vein, petiole 1–3.5 mm long; the apical leaves forming a floating rosette; leaves of terrestrial plants narrowly elliptic, bluntly emarginate, more or less rigid. A ♀ flower in each of a pair of axils or ♂ and ♀ opposed by a solitary ♀, occasionally more than one ♀ with a single ♂. Bracts 0.5–1.2 mm long, translucent, whitish, falcate, persistent. Styles erect or slightly spreading, often poorly developed, 0.2–1.7 mm long. Filament erect, 0.2–2.7 mm long; anthers 0.2– 0. 5 mm long × 0.2–0.6 mm wide, quadrilocular; pollen yellow. Fruit not strumose, subsessile, higher than wide, black when mature, 0.9–1.4 mm long × 0.8–1.1 mm wide, wing mainly toward apex.

Illustrations: —Figures on pages 125 and 127 in Lansdown (2008); Figures 13 (a–b) and 13A(a–b) in Mason (1959). Fig. 10d .

Recognition: — C. palustris can be distinguished from all other Callitriche species by the elongate fruit which are blackish when mature and winged only or more broadly at the apex, with a narrow rim at the base.

Distribution: —Non-native. Within the region, Callitriche palustris has been recorded in a few scattered localities in Victoria, Australia ( Fig. 13 ). Its native range is circumboreal, from Europe east through Russia, the Caucasus, the Himalayas and Mongolia, to China, the Russian Far East, the Korean Peninsula and Japan. In North America, it occurs more or less throughout, apart from extreme northern Canada and the south-eastern United States.

Habitats and Ecology: —There is very little information on the habitat in which Callitriche palustris occurs in the region. It is described as occurring in shallow, still water such as drains, ponds and dams, as well as on mud ( Jeanes 1999, Bean 2007). In its native range, it typically occurs in a wide range of seasonally inundated habitats, including wet ruts on woodland rides, turloughs, lakes, river margins, and reservoirs, as well as occasionally in permanent water bodies. 0–2600 m elevation in its native range, there is no information on elevation in the region.

Conservation Status: —Least Concern ( Lansdown 2016b).

Figures

FIGURE 10. Fruits of Callitriche in Oceania and Australasia: a—C. heterophylla, b—C. insularis, c—C. muelleri, d—C. palustris, e—C. papuana, f—C. peploides, g—C. petriei, h—C. platycarpa, i—C. sonderi, j—C. stagnalis, k—C. umbonata.

FIGURE 13. The distribution of confirmed specimens of C. palustris in Oceania and Australasia