<i>Trientalis europaea</i> L.

Trientalis L. A perennial herb of the family Primulaceae, with a slender stoloniferous rootless rhizome, creeping horizontally close to the soil surface and an erect, glabrous stem 10–25 cm. Adventitious roots, developed on the tuber produced at the tip of each rhizome, occur in the soil surface organic layers. Leaves 10–90 × 5–15 mm, obovate to lanceolate, subsessile, stiff and shining, entire to minutely dentate at the apex, with cuneate base. Leaves (3–)5–8(–10) in a whorl at the top of the stem (occasionally a few alternate leaves below). Flowers usually 1–2 (rarely 3–4), erect (5–)7(–9)-merous, axillary, solitary on capillary pedicels (1–7 cm), ebracteate. Calyx 4–7 mm, deeply divided, teeth linear. Corolla rotate, 11–19 mm in diameter, white or tinged with pink; segments ovate, acuminate or acute; erecto-patent, longer than tube. Stamens (4–)6–7(–8) included; filaments adnate to top of tube. Superior ovary 1-celled, formed by the fusion of 5(–7) carpels; style 1 with capitate stigma. Capsule globose, c. 6 mm, average number two per plant; valves 5(–7) deciduous, leaving the seeds attached to the free-central placenta. The genus Trientalis is a complex of more or less boreal taxa with a circumpolar distribution (Hiirsalmi 1969; Anderson & Loucks 1973; Vergl. Chor., Vol. 2, 1978; Hultén & Fries 1986), including T. europaea, which is the native plant in the British Isles and in continental Europe. Phenotypically, T. europaea exhibits considerable plasticity which is expressed as variation in the morphology of all the vegetative and floral organs (Matthews & Roger 1941; Kovanda 1995). For a polyploid species with a vast geographical range, occurring in a variety of habitats, it is quite surprising that, from the taxonomic viewpoint, this variation appears to be negligible, not producing any appreciable infraspecific units (Kovanda 1995). However, both experimentally determined morphological and physiological differences appear to differentiate ecotypically a subarctic Swedish population from two British populations of T. europaea[see VI (E)]. Trientalis europaea is a native herb of open pine-woods, sessile oak-birchwoods and heather-moors, among moss in damp grassy places, usually rooting in humus, and mostly absent from both the driest and the wettest sites. Trientalis europaea is very local in England (Fig. 1): with a single record for Fritton in East Suffolk, now probably extinguished by flooding and felling (P. Lambley, personal communication); a single record in the Sheffield District of South Yorkshire (Clapham 1969), now effectively the southernmost locality; several localities in West and North Yorkshire northwards into Durham and Northumberland; with two records for north Lancashire (Livermore & Livermore 1987; P. Jepson, personal communication); and four sites in Cumbria (Halliday 1997). Mainly distributed throughout central and northern Scotland with an eastern bias (not recorded from the Inner or Outer Hebrides), locally common. Rare in Orkney (Bullard 1972); on Fair Isle; occurs locally in the Shetland Islands where it is often very dwarf (the so-called var. nana Druce), mainly found in the Dunrossness district of the southern Mainland (Palmer & Scott 1969), but also abundant on the hill behind Grutness, western Mainland (Scott & Palmer 1987). It occurs throughout northern Europe, extending southwards, mainly in the mountains, such as the Bohemian Massif especially in the Sudeten Mountains (Kovanda 1995), to the southern Alps, northern Romania and as far south as Corsica in the Mediterranean (Fig. 2). The distribution of Trientalis europaea in the British Isles. Each dot represents at least one record in a 10-km square of the National Grid. (○) pre-1950; (•) 1950 onwards. Mapped by Mrs J. M. Croft, Biological Records Centre, Centre for Ecology and Hydrology, mainly from records collected by members of the Botanical Society of the British Isles. The main distribution of Trientalis europaea in Europe and western Asia (modified from Vergl. Chor., Vol. 2, 1978; Danton & Baffray 1995; Kaesermann & Moser 1999). The base map is reproduced by permission of the Committee for the Mapping of the Flora of Europe (the bold dashed line shows the limits of Europe). Outside Europe, T. europaea extends eastwards throughout almost the whole of northern Asia to Okhotsk and Kamchatka; to Japan; in western North America, from Alaska southwards to British Columbia, Alberta and into California (Hiirsalmi 1969; Vergl. Chor., Vol. 2, 1978); and more recently recorded as a new species in Greenland (Bay 1993). Trientalis europaea is included in the northern montane element (Dist. Br. Fl.) and classified as circumpolar Boreal-montane by Preston & Hill (1997). The altitudinal range of T. europaea in the British Isles extends from sea level on the east coast in Aberdeenshire, Scotland to an upper limit of 1082 m on Lochnagar (Matthews & Roger 1941). It ascends to 600 m in northern Norway, to 1000 m in northern Sweden and to 1580 m on Jotunheimen, southern Norway (Atl. N.W. Eur.); up to 1380 m in the Hrubý Jeseník Mountains, Czech Republic, up to 1430 m in the Böhmerwald, Germany, to 1635 m in the Tatra, Slovenia, to 1400–1700 m in the Tirol, Austria (Vergl. Chor., Vol. 2, 1978), up to 1800 m in France (Danton & Baffray 1995), and in Switzerland in the cantons of Schwyz to 900 m, of Bern to 1400 m, of Ticino to 1700 m and of Grisons (= Graubünden) up to an altitude of 1900–2100 m (Kaesermann & Moser 1999). The 15.6 °C July mean isotherm approximates to the southern (lower) distribution limits of T. europaea in the British Isles (Atl. Br. Fl.). The geographical distribution and altitudinal restriction at the southern limits of its range in Europe correlate well with relatively high mean summer temperatures, i.e. limited by high temperatures. It has been demonstrated experimentally that the optimum temperature for carbon assimilation in T. europaea is 11–18 °C and that it declines at higher temperatures [see VI (E)]. Absent from the most open and most deeply shaded sites; characteristic habitats include moderately shaded sites in coniferous and deciduous woodland, and in treeless heathlands beneath the canopies of Calluna vulgaris, Juniperus communis, Myrica gale or Pteridium aquilinum. Less T. europaea occurs in open and as of a It has been that the of T. europaea is in open as to shaded sites [see VI (E)]. Trientalis europaea is a found on which surface The of an of in the leaves of T. europaea in native sites that is very the but with the leaves appear to the of the and the to 2). However, in with T. europaea is more to of or by than assimilation The species has also been to occur on a in and on a in a & in northern T. europaea also occurs on an with a of in and in with a of & The National records T. europaea in a range of It is in the of in where the shows has with in in and Br. and in the and of in Aberdeenshire, T. europaea has been to occur locally in in which has been a with on from & Br. and T. europaea and differentiate the which is found in the eastern mountains, from the in the T. europaea is in the of which occurs in the more continental of eastern is to the with of Trientalis europaea is in Juniperus at high the of the of the and a variety of of or woodland, more and less including that by in the National in the in of a with and to and northern Swedish this T. europaea is a species which occurs a more or less but of communis, both where the is open in the Juniperus and in the treeless Juniperus & Trientalis europaea is in especially in the eastern in the and native in Scotland & where T. europaea is to locally in a moss in a moss in both a and a and in a It also by & in the where T. europaea is distributed in the and in the to & T. europaea, which is a species of the is in the and in at in Trientalis europaea is in in the which is the of the of It is in mainly in the of Scotland as by & and also in in the western of Trientalis europaea is also found in two Calluna in the Scotland and the North and in Calluna which occurs but locally the of especially in the Shetland T. europaea occurs locally in a few including a very the southern tip of south Mainland c. m mean sea which in and summer is in this it is with at least species in a and including Calluna vulgaris, and personal the in the of in the the is by including of such as Trientalis europaea, and the in the of northern T. europaea occurs in open in which is the most abundant the is of the T. europaea is in the and and in the & continental extends southwards in on the eastern of the is the of on with a humus, in the but also in southern Sweden in the this of the is usually by with or and Trientalis europaea a local the T. europaea occurs in in which is usually the but is also Europe, the boreal species and Trientalis europaea species of the Trientalis europaea, an plant of and also occurs in the east of the northern in Europe on as in the in the of in It is by as a species of in the with Juniperus P. P. and several of the Bohemian T. europaea occurs in and (Kovanda 1995). the & record T. europaea as in both and Trientalis europaea is in in the of Europe, and as a species of with as in the at c. It is also found in Calluna in the in Calluna in is T. europaea is a species in the in Europe is into a coniferous T. europaea is a species with and in the subarctic of northern in an of var. in by the of the of the more the the the of the in more to the and Trientalis The mean of the species the in the & from collected in and in an from in boreal north of southern found in the The main a in the of species and the of of species such as Calluna vulgaris, Trientalis europaea, and The as by the and of and & 1999). in the in a and to a & the T. europaea and the of but of the that produced produced than of and and not and of any in in a in a However, in collected in from of T. europaea, and by the in of the The of by on in a two and in the and in the a higher level in the more A has determined the of by in to the of T. europaea of populations been in an in the of this to is in on The sea level of an is with and with the it by of T. europaea be in populations with a of in The of to be to the of population in T. The of a of a population of T. europaea in an that the of by and the than in the and not by and the number and of all of which with a on the level of and of the in a of the in the of this The T. europaea, and two and has been in a on on the sea by & (1997). The that both the and the to the in a in and a higher level than found in the that the not but also a by the of of by and and of by been in a population of T. europaea occurring in a in Sweden The of by not any of plant all of the of T. and summer and tuber produced and which in a and produced in the Trientalis europaea in sites to a by vegetative [see VI A of this from the of each new or also from a the plasticity of of T. europaea developed from in to four of in in a The shaded by a which to of the of to of a and and a with morphological plasticity to the of as well as to an of distributed in native also to variation in at higher of the produced but than at also be of for the and of in the The morphological to has also been in a in a in Sweden by from the in to the of with an or all with and produced more and a main not by the with of the of variation in the morphological to be A & with from the to the population of T. europaea in a The that the species at its in but this by The of this at the level that mainly to the of in the or that a by the of and the of The and at which the of in that the of the morphological in T. europaea is by a high in the of the of T. europaea been on the in a of and also in an in the and by the of any J. & J. both localities the plant locally abundant a of from the two considerable the main of vegetative but the of in T. europaea, in most and in × in a × m in each of the two each × m at from the to at least for the of mean and mean at the and the also but in the for the native and The in leaves collected from the two with from an open and a in a July and and not in all four sites. However, in the open sites than in the the of in the open habitats an to the higher of expressed in the of the in all four sites a to that for & and for two and at northern by in T. europaea from to with the of the for a range of habitats by J. and J. at in an of by Calluna vulgaris, to by Juniperus The mean of T. europaea in × in the and in open at The mean of from shaded with from open the also at or for of the from the open but from shaded both and the habitats the of T. europaea in open as to shaded and with the higher of and temperature in the to a in carbon assimilation on [see VI (E)]. The of and on the of the treeless which and at has been by the most in of from the Trientalis europaea and the at Shetland on an sea top that T. europaea an average population of of which in any and the in more than 6 high personal in the the of T. to mainly the an to level temperatures of to °C in southern in such that the and A of has a the and is less than an in the of a the of the produced in the summer from the on the of the and each tuber to rootless which usually with to the soil surface at a of cm. to by the most often mm and a of cm. the tip of each to a new tuber 1 and mm in with a of is by Kovanda the the Adventitious from the tuber and most often to a The of both and a single from the of each leaves and in a whorl of leaves and the to T. europaea also which from at the base of the main stem the soil often than the main but also from the of the (Hiirsalmi from from the of the leaves of the erect The in the as the stoloniferous the surface of the soil and the to The in the of T. europaea by and to of T. and by Anderson & Loucks recorded of for on the upper surface of the and on the the of leaves collected on in by from in southern the mean of and of T. europaea collected in from for a level of found of the & 1997). of the of but or & J. personal & record both the and of in T. europaea from continental Europe. The plant is by to be in a in northern the one to each with a a produced at the base of the the of which in each from the of the rhizome, a single and from the of the the species a of and and has been as a by vegetative is in habitats and for the relatively from (Matthews the from sites in the Bohemian Massif by Kovanda all of the of one single plant from in populations of T. europaea has been experimentally in a coniferous in Sweden & two up and and with four of the of the seeds of T. europaea into each For up to developed in the with in the and in both The experimentally and both a on a of and a by a and in to T. europaea and a of seeds of T. europaea in of each and seeds of in of each The plant T. europaea, with an an almost on for a few seeds a of in the with a in each of the two the which exhibits a to a by with a of and a in the two The and of T. europaea been in in a in Sweden by & a the population of of or from a with a of The number and of the and to the of the A to a tuber of a to the has a with as units of both and The main tuber has a i.e. it a that the in the produced an in the number be in the the of found to be in of the in the tuber for A polyploid species with a number of in from southern (Hiirsalmi and from the Czech (Kovanda 1995), the of which by leaves of T. europaea by J. and J. on and on the and for and of temperature and an to an to a range of and at on and in the assimilation higher in the leaves of in the open than in shaded on and in the A in shaded than in in the open differences and sites The of in the open to to not a of in the two populations mean mean also of with to the & & in the a The from the is an of the of in and is as a of of the of T. europaea a of the with the usually found in leaves below). of and which the of including its of by the leaves of T. europaea from collected on the and in with the A range of in by at each for to the of and as leaves been in the for both a temperature of °C and at carbon (Fig. and A a at c. as the from the A at high in T. europaea is by boreal in and the of also at c. to almost in as a of and to the for in T. europaea and and not with or temperatures. A carbon assimilation and temperature in in at temperatures and and two of and The of carbon assimilation °C and on to for T. and & higher temperatures A in T. europaea the but this and the temperature at c. the higher a more to a of any carbon at temperatures with temperature but the not to the in at the higher mean for and of of T. europaea, and with temperature or of carbon in leaves of Trientalis europaea at of at two temperatures, °C and of for and J. and J. The in A at and temperature is or by For by of T. europaea at to the at leaves to high at higher A than at that the carbon by T. europaea, at and relatively temperatures, at least in a of carbon has and mean of of T. europaea in open where both temperature and to be than of shaded [see The of of T. europaea collected from to a range of temperature and been experimentally by J. and J. collected at northern Scotland and North from and in a 1 1 of and at and to for in a range of temperatures, at of (Fig. the of by the Swedish population less than of the Yorkshire and populations of at °C and on the of the Swedish a range of both temperature and The collected from produced which more and leaves than the Yorkshire and assimilation A in leaves of Trientalis europaea to a range of temperatures, at of of populations North northern The and of in T. europaea been by and in the the of the throughout the the mainly in the the The in the both and of of the for and However, the which to a a of the with is the of a species with two and the of a of such It is that from However, by western has that the to a of and the is of a is to the plant The of in and of T. europaea, in summer and and appear to a central in & 1997). Trientalis europaea as a tuber which horizontally a few the soil the of each tuber to to a new the leaves and the that the The leaves in in northern few also from the tuber in and by The of each to and the tip to a new tuber which to its by the of The the in it to the of the the tuber with the formed The often erect throughout the and the seeds attached occurs in and is and the to of T. europaea, the ovary including the is developed the the style and not throughout the on The than the filaments and found in quite formed at this the the the of the filaments is and the on a level with the stigma. However, not has for The is at a the and style to the the into with from its and However, is not with be negligible, and with a it be almost for any to the is and and the is in a is probably as to from as from to & Roger and the The is the main in is but the is to the at the base of the and in it and the one of its the and the the stigma. occur the several such as also to the mainly on of the at the in the The is also a to the is it is quite that, the range of the main not be the species throughout the range of T. in in and the mean number of seeds per by in a but with a mean number of seeds per of the of the of is by the for with a mean number of seeds per of (Hiirsalmi is of at least in the at Scotland [see in produced by a mean of a in the in from a mean of produced with a mean of seeds per & Roger found that from 1 to with an average of seeds per less than the number of each plant of T. europaea two on average the it is that the of any population be relatively The or of be to of which and minutely by a formed by the of the for several the of the seeds (Matthews & Roger 1941). of the seeds formed by a population been by the of or the attached to the top of the or the (Matthews collected in Scotland by & Roger a mean of of collected by a mean of southern and from each of two sites in It is very for the seeds of T. europaea to on soil a of but this that (Hiirsalmi The is very that it for the to to the to and the The to temperatures which occurs in the the seeds this occur in the four found that the of of T. europaea collected in in but on of in in of the in which to a of temperatures to at with the The mean for all in or in a in of the seeds of including T. europaea, by in the of a north Swedish coniferous each in of of in A of and for in each of the in and and in seeds in an on at °C with from of seeds of T. europaea in the very The in the with all the and a of the seeds found in the soil not in the in the soil in the the and of T. europaea which a in is The of in T. europaea to in the as the usually very and be the of the attached to the is the most of from from very (Hiirsalmi in the of in the in the the and extends The has a and a of behind the The to in the for a and at the soil The glabrous the The and leaves more or less with a base and a of seeds and A with and the two more or less alternate leaves is by in the of seeds of Trientalis europaea at temperature at °C for 6 on a in a to The which has a range, mainly of including T. europaea summer a Swedish with an of and found to be the on the of T. europaea in the The and also on the also is a on a number of T. europaea it on level & 1997). also & a on leaves and of T. europaea & The the plant and the and of the on the of the been by & & and is found on leaves of T. europaea & the recorded British of T. europaea collected in in the of Scotland by J. & to the T. & for in and and to and J. for the for to for from northern also to for for a of from the Botanical of Mrs J. M. for 1 from the Biological Records Centre, P. for from the base by Lancashire and for of distribution and of the and the for permission to and from the British Society from the of and the of a to

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