188 ANGIOSPERMAEDICOTYLEDONES 



protandrous, and when they open the five outer stamens first bend inwards and 

 dehisce, the five inner ones being as yet unripe and curved outwards, and the 

 stigmas immature. Before the anthers of the five outer stamens have withered, 

 those of the five inner ones dehisce, but still remain directed outwards. As they 

 wither, the styles elongate, and the stigmas unfold above the contracting and 

 shrivelling stamens. Every insect that is not too small must, therefore, when trying 

 to get at the nectar, dust itself with pollen in the younger flowers, whether it alights 

 in the middle or at the edge; while in older flowers it is obliged to touch the 

 stigmatic papillae, thus effecting cross-pollination. Failing insect-visits, the stigmatic 

 branches bend back still more, coming into contact with the anthers to which pollen 

 still adheres, and in this way automatic self-pollination takes place as a last resource 

 (see Fig. 56). 



Besides these protandrous hermaphrodite flowers, the mechanism of which 

 has been thus described by Hermann Miiller, there are small female ones, with 

 quite vestigial stamens of white colour, and also medium-sized transitional forms, 

 with 2-3 stamens developed (e. g. in Belgium, according to MacLeod). The plant 

 is gynodioecious in Sweden (Tullberg), and by the Altenfjord (Warming). Schulz 

 observed gynomonoecism, as well as gynodioecism, in Central Germany, where in 

 some localities the stocks may be mainly or exclusively female. He noticed herma- 

 phrodite flowers of three different sizes, i.e. 8-10 mm., 10-14 mm., and 16-18 mm. 

 in diameter. These seem to be local. The larger flowers are not visited by more 

 numerous insects than the smaller ones. 



Visitors. Schulz observed flies, small bees, and beetles. In the Alps, where 

 Lepidoptera abound, Herm. Miiller saw a butterfly. He (H. M.) and myself (Kn.) 

 have observed the following in North and Central Germany: A. Coleoptera. 

 Nitidulidae : 1. Meligethes, skg. and po-dvg. (H. M.). B. Diptera. (a) Empidae : 

 2. Empis livida Z., skg. (H. M.). (b) Syrphidae : 3. Eristalis tenax Z., skg. (Kn.) ; 

 4. Helophilus pendulus Z., skg. (Kn.); 5. Syritta pipiens Z., skg. and po-dvg. 

 (H. M.) ; 6. Volucella bombylans Z., skg. (H. M.). 



Verhoeff saw the following in Norderney. A. Coleoptera. (a) Nitidulidae : 

 1. Brachypterus gravidus ///., skg. B. Diptera. {a) Empidae-. 2. Hilara quadri- 

 vittata Mg., skg. (b) Muscidae : 3. Anthomyia sp. (c ) Syrphidae : 4. Melanostoma 

 mellina Z., skg.; 5. Syritta pipiens Z., skg. C. Hymenoptera. (a) Formicidae: 

 6. Lasius niger Z., skg. 



MacLeod noticed Apis, 6 Syrphids, an Empid, 2 ichneumon-flies, a Siricid, 

 and a Lepidopterid in Flanders (Bot. Jaarb. Dodonaea, Ghent, vi, 1894, p. 164). 



In Dumfriesshire, an Empid, 2 hover-flies, and 4 Dolichopidae have been 

 recorded (Scott-Elliot, 'Flora of Dumfriesshire,' p. 29). 



468. S. cerastioides L. (Herm. Miiller, 'Alpenblumen,' pp. 188-9.) The 

 number of carpels is variable in the homogamous flowers of this species. 



Visitors. Herm. Miiller saw Diptera (an Empid, 2 Muscidae, and 4 Syrphidae) 

 in the Alps. 



469. S. HolosteaL. (Herm. Miiller, 'Fertilisation,' p. 135; ' Weit. Beob.,' II, 

 p. 228; Kirchner, 'Flora v. Stuttgart,' p. 238; MacLeod, Bot. Jaarb. Dodonaea, 

 Ghent, Hi, 1891, p. 378; vi, 1894, pp. 162-3; Schulz, 'Beitrage,' I, p. 22; Knuth, 

 ' Bloemenbiol. Bijdragen.') 



