348 



ANGIOSPERMAEDICOTYLEDONES 



Jaarb. Dodonaea, Ghent, vi, 1894, p. 144; Kirchner, 'Flora v. Stuttgart,' p. 216I 

 Verhoeff, ' Bl. u. Insekt. a. d. Ins. Nordemey'; Knuth, ' Beitrage.') The flowi 

 mechanism agrees with that of the preceding species ; there are, however, usua 

 six to eight, more rarely five stamens, which are of about the same height as 

 three stigmas, and mature simultaneously with the anthers. The flowers are sma 

 and pink, or more rarely white, in colour. There may be pseudo-cleistogamy as in 

 P. mite. 



Visitors. Herm. MuUer observed 4 hover-flies i . Ascia podagrica -F., skg. ; 

 2. Melithreptus menthastri L., skg. and po-dvg. ; 3. M. pictus Mg., do. ; 4. Syritta 

 pipiens L., skg. 



2480. P. aviculare L. (Herm. Miiller, 'Fertilisation,' p. 515; MacLeod, Bot. 

 Jaarb. Dodonaea, Ghent, vi, 1894, p. 144; Kirchner, 'Flora v. Stuttgart,' p. 216; 

 Verhoeff, ' Bl. u. Insekt. a. d. Ins. Nordemey ' ; Knuth, ' Beitrage.') The flowers 

 of this species are very small (scarcely 2\ mm. in diameter), and green in colour, 

 with purple-red or white edges. As they are devoid of nectar and odourless, and 



situated singly in the leaf-axils, they possess 

 very little power of attraction and very rarely 

 receive insect-visits ; they are, in fact, almos 

 limited to automatic self-pollination, which 

 very effective, as almost all flowers set fruil 

 The perianth leaves diverge widely. Th 

 five stamens that alternate with them bend 

 outwards, while the three others bend inwards, 

 so that they are brought just above the two 

 stigmas, which mature simultaneously with 

 ihem. Automatic self-pollination is therefore 

 inevitable by fall of pollen. When the flowers are visited by insects either self- or 

 cross-pollination may be effected with equal facility. Although the filaments possess 

 a fleshy thickening at the base, no secretion of nectar is to be found, the flowers 

 offering only pollen to visitors. Hermann Miiller observed, however, that Syritta 

 pipiens not only devoured pollen, but inserted its proboscis into the base of the 

 flower : it either sought nectar in vain or licked off a shallow layer. 



Visitors. The following were recorded by the observers, and for the localities 

 stated. 



Verhoeff (Nordemey), the hover-fly Syrphus corollae F. Knuth (Kiel), tfc 

 hover-fly Syrphus balteatus Deg., po-dvg. Herm. Miiller (Westphalia), 3 hover-flies- 

 I. Ascia podagrica F., po-dvg.; 2. Melithreptus menthastri Z., do.; 3. Syritta pipiei 

 L., and perhaps also skg. 



2481. P. Convolvulus L. (Kirchner, ' Flora v. Stuttgart,' p. 212; Knut 

 ' Bl, u. Insekt. a. d. nordfr. Ins.,' p. 166.) The flowers of this species belong 

 classes C to EC. Although they are situated in fascicles in the leaf-axils, they recei\ 

 few insect-visits on account of their small size and the inconspicuousness of the greei 

 white-edged perianth. Kirchner says, therefore, that they are almost entirely restrict 

 to automatic self-pollination. Anthers and stigmas mature simultaneously ; but 

 flowers at first open so widely that these organs do not come into contact. Graduallj 



Fig. 355. Polygonum, aviculare, L. (after 

 Herm. Mailer), (i) Flower seen from above. 

 (2) Do., after removal of the two front perianth 

 leaves and half the stamens ; seen from the side. 

 a and a', inner and outer stamens ; <w, ovary ; 

 St, stigmas. 



