PAPA VERA CEAE 63 



sky-blue anthers dehisce before they open, and pollinate the already mature stigmas. 

 The bluish, spherical pollen-grains are opaque owing to the presence of minute 

 wart-like projections. Their average diameter is 50 p. 



Visitors. I observed at Kiel a hover-fly, Platycheirus podagratus Lett., 

 po-dvg. 



135. P. somniferum L. (Kerner, 'Nat. Hist. PI.,' Eng. Ed. 1, II, p. 190; 

 Kirchner, 'Flora v. Stuttgart/ p. 278; Knuth, 'Bl. u. Insekt. a. d. nordfr. Ins./ 

 pp. 22, 148.) The petals are either carmine to violet in colour, often blackish at 

 the base, or else white with a lilac base. The flowers agree in structure with those 

 of P. Argemone and P. Rhoeas, but in the bud the anthers project over the stigma- 

 lobes which are still folded down so that before anthesis not only the lower but 

 all the stigmatic papillae are thickly covered with -pollen. This automatic self- 

 pollination is partly effective. Owing to the size of the flower, however, insect-visits 

 are very numerous, so that in favourable weather cross-pollination is assured. The 

 Diptera (Syrphidae) which I observed visiting the flower almost always alighted upon 

 the large upper-surface of the pistil with its radiating stigmas from which the 

 stamens move away when the flower opens and then go to the anthers, so that 

 cross-pollination must be effected by a second visit. The humble-bees observed by 

 me as visitors only now and then touched the stigmas, for they almost always 

 alighted upon the crowded stamens, and then wandered about among these collecting 

 pollen. Warnstorf (Ver. bot. Ver., Berlin, xxxviii, 1896) describes the whitish pollen- 

 grains as ellipsoidal, with a length of about 44 /*, and a breadth of 28 /x. 



Visitors. The following insects have been observed by Buddeberg (Budd.) in 

 Nassau, and by myself (Kn.) in Schleswig-Holstein. 



A. Coleoptera. (a) Scarabaeidae : 1. Cetonia stictica Z., devg. the flowers 

 (H. M.). (b) Nitidulidae : 2. Meligethes sp. (Kn.). B. Diptera. Syrphidae : 3. 

 Eristalis aeneus Scop. (H. M.) ; 4. E. arbustorum Z. (H. M., Kn.) ; 5. E. tenax Z. 

 (Kn.); 6. Platycheirus peltatus Mg. (Kn.) ; and 7. Syrphus sp. (Kn.), all po-dvg. 

 C. Hymenoptera. Apidae : 8. Apis mellifica Z. 5, freq. (Kn.) ; 9. Bombus terrester 

 Z., freq. (Kn.) ; 10. Eriades campanularum K. 5 (H. M.) ; 11. E. truncorum Z. 5 

 (H. M.); 12. Halictus cylindricus F. 5 (H. M.); 13. H. leucopus K. $ (H. M.); all 

 po-cltg. 



136. P. dubium L. (Herm. Muller, 'Fertilisation/ p. 94.) Automatic self- 

 pollination is rendered difficult in this species because the anthers stand a few 

 millimetres below the stigma; it can therefore only take place in flowers which 

 are bent downwards. Hermann Muller is of opinion that the very great rarity of 

 this plant in some districts is perhaps due to the impossibility of autogamy. Warnstorf 

 (Verh. bot. Ver., Berlin, xxxvii, 1895) describes the pollen as yellow, spherical to 

 ellipsoidal when examined in water, marked with several longitudinal furrows, and 

 31-37 /x in diameter. 



Visitors. MacLeod in Flanders observed small flies (Bot. Jaarb. Dodonaea, 

 Ghent, vi, 1894, p. 186). 



In Dumfriesshire (Scott-Elliot, ' Flora of Dumfriesshire/ p. 8) there have been 

 noted 3 Muscidae, a hover-fly, and Meligethes. 



137. P. argemonoides L. Hildebrand states that this species is fertile when 

 self-pollinated. 



