Flora of Ashdown Forest - Botanical Society of the British Isles

68Viola riviniana. Common dog-violet.Common on the Forest (Hall 1980).This is the commonest violet on the Forest, in hedges, woodland, road verges, banksand on tracks. It is also variable, as elsewhere in Britain. Good' V, riviniana' has quiteyellowish spurs to the flowers and there are some very good, distinct populations on theForest. Others have broad, purplish spurs; these are currently interpreted as hybrids with V.reichenbachiana, and some of the populations are mapped separately (see below), Plantswith pale bluish flowers occur on road verges immediately east of King's Standing.Cranfield transplanted 24 boxes of violets within his woods at Broadstone Farm to anarea with oaks as a food plant for the silver· washed fritillary (AFN 14: 14·17). The flowersare also regularly eaten by slugs and insects and small holes can be seen in the spurs where they have been robbed bybees. If there are few pollinators around during the main flowering period in the spring seed set would be very low, wereit not for seed production by the cleistogamous flowers which are produced all summer (Beattie 1969).Almost ubiquitous in Sussex and Britain. Widespread in Europe except in the south-east, and in North Africa.Viola x dubia (V. reichenbachiana x rivinianaj.Plants with purple spurs seen on Ashdown Forest were regarded as hybrids by JK in 1995,and differ from European V. riviniana; most were reasonably fertile. They are widespreadboth on and around the Forest (e.g. woodland at Toll Lane, Boringwheel Mill, Wych Cross,Parrock Lane), and may be quite widespread in Britain. Their interpretation depends on thespecies concept of V. riviniana, which seems to be broader in Britain than on the Continent.In Europe and Britain, the two parents tend to be partially ecologically separated, V.riviniana in the open and V. reichenbachiana in woodland though there is considerableoverlap in their ecological requirements. Where their habitats are fragmented they come into4 5contact regularly, and this may have resulted in extensive hybridisation.The parents overlap in flowering time, V. reichenbachiana usually coming into flower before V. riviniana, and thepollinators are not specific. Flowers of both species usually last about 7-14 days. Initially the flowers are designed forpollination by a few specific insects such as bees which can operate the pollination mechanism; they are attracted to thenectar which can half fill the spur. Later, the floral organs and the way that the pollen is presented change considerablyas the flowers age and the pollen can be transmitted between flowers by many generalist pollinators (Beattie 1969).Viola reichenbachiana. Early dog-violet.This species occurs in woodland on clay soils, as at the copse near Mudbrooks House1403.3391, pH 6.3, 1995, TR & PA, or the woodlands at Toll Lane (460.263· tetrad 42T inHall 1980), pH 6.5, 1993, TR & NM where it also occurs on the verges, and at FurnaceWood (47.26), 1994, TR & SR. It was also recorded in tetrad 42P in Hall (1980) which3 looks odd as there are no suitable soils.4 5It is widespread in woodlands 'In lowland Britain, Europe, Caucasus, Kashmir, Moroccoand Madeira.Viola seeds are dispersed either purely by ants attracted by a caruncle which providesfood, or by explosive ejection of the seeds followed by dispersal by ants (Beattie & Lyons1975). Seeds of most species such as V. riviniana and V. reichenbachiana are dispersed explosively first by the capsuleswhich split into three segments, and then may be carried further by ants. Only a few Eurasian species such as Violaodorata and V. hirta are dispersed purely by ants (possibly those of the genus Formica). The plants show variousadaptations of the capsules and seeds; those with ballistic dispersal have fruits held on erect peduncles and small, shinyseeds with a small caruncle. Capsules of species dispersed purely by ants tend to be held near the ground and have largeseeds with tough coats and a large caruncle as bait. Seeds of both groups germinate better when they have beengnawed by ants, but some seeds get eaten completely.[Viola canina. Heath dog-violet.Coleman (1836) recorded Viola flavicornis (a variety of "Viola canina" with deeply cordate leaves) from Ashdown Forest,but the exact identity of his plants is unknown.We await confirmation of the presence of V. canina on the Forest, including the unverified records for tetrads 43Land 43W in Hall (1980). True V. canina occurs nearby on Halt ye Common and possibly still on Chailey Common, and itmight be expected from Ashdown Forest. One possible plant occurred on a track at Wych Cross Place (418.316), 1987,PW & RW, but has not been refound.Plants need to be carefully checked, and some records may arise from non-experts assuming that "dog violets" areV. canina rather than the very common V. riviniana. Historically, both V. canina and V. riviniana were included in thesame species giving further potential for confusion.]