Hypericum maculatum subsp. obtusiusculum, (Tourlet) Hayek Hypericum perforatum, L.

(b) Subsp. obtusiusculum (Tourlet) Hayek , Sched. FI. Stir. Exsicc. 23-24: 27 (1912):

Inflorescence-branches making an angle of c. 50° with the stem. Sepals erose-denticulate, wide to narrow. Petals with a few marginal black glands, and superficial ones mostly in the form of long streaks. 2«=32. Lowlands o f N. W. Europe from W. Germany and the Netherlands westwards, and in the Alps at lower altitudes than subsp. (a).

54. H. perforatum L., Sp. Pl. 785 (1753)

( H. noeanum Boiss. ).

Stems 10-100 cm, erect from a decumbent, rooting base, 2-lined. Leaves (5—)8—30(—35) mm, ovate to linear, sessile or subsessile, with obscurely reticulate venation and with numerous large translucent dots. Sepals lanceolate or oblong to linear, acute to acuminate or shortly aristate, usually entire, without or with a few superficial black dots. Petals with a few marginal black dots, sometimes also with superficial black dots or streaks. Capsule with dorsal vittae and lateral, oblique vittae or vesicles. 2zz = 32 (?48). Throughout Europe except the extreme north. All except Fa Is Sb. Very variable. Most northern plants have relatively wide leaves; but towards the south of Europe plants with narrow leaves ( var. angustifolium DC. ) or small leaves ( var. microphyllum DC. ) are predominant. Although these southern plants have been found to differ genetically from the wide-leaved ones, there appears to be no morphological discontinuity between them. Reproduction in H. perforatum has been shown to be 97 % apomictic (pseudogamous), resulting in the formation of unreduced embryo-sacs with 32 chromosomes. The pollen, however, undergoes normal meiosis. Hybrids with diploid species (2/7=16) are, therefore, pentaploid if H. perforatum is the female parent and triploid if it is the male parent. Triploid hybrids are more or less intermediate between the parents, but pentaploids are usually almost indistinguishable from H. perforatum . Two hybrids of this type have been described: 51 x 54 ( H. x medium Peterm. ) which is rather rare, owing to the different habitat-preferences of the parents, and 53 (a) x 54 (H. x desetangsii nm. carinthiacum (A. Fröhlich) N. K. B. Robson ( H. carinthiacum A. Fröhlich )), which is fairly common in E. Europe.

53(b) x 54 (H. x desetangsii Lam otte nm. desetangsii) is, however, tetraploid. It is common and apparently fertile. The primary hybrid is intermediate, with stems usually with 2 strong and 2 weak lines; leaves with laxly reticulate venation and a few pale glandular dots; sepals narrowly oblong or ovate-lanceolate, with the apex apiculate and erose-denticulate. Back-crossing has, however, produced a complete series of intermediates between the parents.