ROSACEAE 359 



In this species, besides the hermaphrodite flowers described by Ricca, A. Schulz, 

 and Lindman as protogynous, and by Hermann Miiller as functionally protandrous, 

 there are unisexual ones distributed androdioeciously (Miiller), or andromonoeciously 

 (Schulz), and these male flowers are on an average smaller than those which are 

 hermaphrodite. Failing insect-visits, pollen must fall upon the stigmas from the 

 stamens (which almost reach their level) owing to the oblique position of the flowers, 

 so that automatic self-pollination results. On the other hand, owing to the pro- 

 jection of the stigmas, crossing is usually effected by such visits. 



Kerner (' Nat. Hist. PI.,' Eng. Ed. i, II, p. 381) describes the flowers as proto- 

 gynous, and gives the following account of their mechanism. — The stamens, which 

 curve inwards in the bud, straighten themselves only a short time before the anthers 

 dehisce. The anthers of the outermost whorls dehisce first, so that to begin with 

 autogamy is excluded owing to the distance between stigmas and anthers. 

 At this stage insect visitors which alight in the middle of the flower and creep out- 

 wards to collect pollen or lick nectar effect cross-pollination. The inner stamens 

 now straighten themselves, and their anthers dehisce. These are now at the same 

 level as the stigmas, which are still receptive, and consequently get self-pollinated. 

 This is favoured by the outward inclination of the external carpels. The automatic 

 self-pollination of the stigmas of the inner carpels, should insect-visits fail, is brought 

 about at the end of anthesis by the bending of the peduncle to an extent that brings 

 them into the line of fall of the pollen. 



On the Dovrefjeld, Lindman noticed protogyny followed by homogamy, but 

 not dioecism. Warming, on the other hand, observed that in Greenland the flower 

 mechanism is the same as in Europe. Ekstam gives 10-25 rn™- for the diameter 

 of the odourless, homogamous flowers examined in Nova Zemlia. Automatic self- 

 pollination is possible. 



The species flowers in Spitzbergen from the end of June to the end of August, 

 or even longer, and sometimes sets numerous fruits (Andersson and Hesselman, 

 'Bidrag till Kanned. om Spetsbergens o. Beeren Eil. Karlvaxtflora,' pp. 20-1). 

 Ekstam (' Blutenbiol. Beob. a. Spitzbergen,' p. 10) says that the flowers there are 

 faintly fragrant, and 20-7 mm. (exceptionally 28-38 mm.) in diameter. Self- 

 pollination can easily take place, for the anthers dehisce almost immediately over 

 the stigmas. The peduncle elongates considerably after anthesis. 



The variety unguiculata, discovered by Nathorst, possesses a form of flower 

 which deviates markedly from the ordinary type, for the petals narrow at their bases 

 into a claw 4 mm. long, and radiate squarrosely, while the petals are bent inwards 

 (Andersson and Hesselman, op. cit.). 



According to Abromeit, the flowers of the variety intermedia Nathorst, which 

 unites the group-forms D. octopetala L. and D. integrifolia Vahl, exhibit slight 

 protogyny and slight protandry, as well as homogamy (' Bot. Ergeb. von Drygalsky's 

 Gronlandsexped.'). 



Visitors. — Herm. Miiller saw in the Alps numerous bees (especially Halictus 

 sp.), and Diptera (particularly Muscids), as well as some beetles and Lepidoptera. 

 Frey (Switzerland) noticed the Tineids Ergatis heliacella H.-S., and Tinagma 

 dryadis Stgr. 



