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58HUGO SJORSFig. 8 . . vernal hazel (Oorylus avellana) at its northernmoststation in Sweden, growing on a sunny slope with signsof soil creep that counteracts podsolization, and goodmoist soil; twigs partly pressed down by excessive snow.Balberget, Bjurholm, NE Angermanland. May 20, 1961.Photo 0. Rune.typical part. The subzonation was discussed, andit was found that, in Sweden, both the northernconiferous forest region and the subalpine birchwoodland region are parts of the Boreal zone. Onthe continents (Fig. 2) four Boreal subzones are discernible.A southern and south-eastern part of thenorthern coniferous forest region of Sweden correspondsto the "Southern Boreal" subzone. Thegreater part of the North Swedish forest land fitsinto the second subzone (the "Main Boreal"),whereas the pre-alpine or high-level coniferous forestbelt as well as the lower. parts of the subalpine beltcorrespond to the "Subarctic" subzone of the Borealon the continents. Only the uppermost subalpinewoodlands in the Scandes (and near the northcoast of Norway) correspond to the "Woodland.Ac'ta Phytogeogr. Suec. 50Tundra" subzone on the continents. The subalpineregion will not be discussed further in this articlebecause it will be treated by 0. RuNE and by H.HoLMEN. The pre-alpine coniferous subzone willalso to some extent be dealt with by them, and inWISTRAND's contribution, too.The subzonation found in Finland (KALELA1958, 1961, etc.) is similar to the continental exceptfor a subzone called Perapohjola intercalatedbetween Main Boreal and Subarctic, and probablymost similar to the latter.Opinions differ as to the number of recognizablesubregions in Sweden. Du RIETZ, partly followingWAHLENBERG (1824-26), finds it possible to distinguishthe following subregions within his ''northSwedish oak-less conifer forest region" (1950 e, 1952,1964, p. 310).(1) An "ash subregion" of very narrow extension,just north of the oak-line.(2) A "north Swedish maple-linden-hazel subregion"with scattered spontaneous occurrence ofAcer, Tilia and Corylus and other essentiallyNemoral species. In the coastal area it reaches asfar north as Ornskoldsvik (southern Angermanland),in the inland to Lake Siljan, if some outpostlocalities are left outside.(3) The "north Swedish Myrica subregion(without spont:meous maple, linden and hazel)".It includes the coastal areas on the Bothnian Bay,and an inland zone of variable width. In this subregion,M yrica gale is still usually frequent, andAlnus glutinosa and several other comparativelywarmth-demanding species still occur.(4) The "central conifer forest subregion ofnorthern Sweden" situated inland of subregion (3),with a small proportion of southern species only(e.g. Betula verrucosa).(5) The "pre-alpine conifer forest subregion",at comparatively high levels only, to the greaterpart along the eastern fringe of the Scandes, butwith outlayers on high hills farther east, and reachingfarther west in mountain valleys.In an early paper (1950b), the present author didnot feel it readily practicable to keep subzones (1)to (3) apart, but in the paper of 1963 (a) only (1)and (2) were lumped, and (3) and (4) were groupedtogether as "Main Boreal", in order to conform to