APOCYNACEAE 



87 



dehisce introrsely. Their margins are hairy, so that the pollen can only fall upon 

 the terminal brush of the disk. Nectar-seeking insects can insert their heads for 

 several millimetres into the corolla tube, as far as the brush, so that a proboscis 8 mm. 

 long is able to reach the nectar. When this is inserted it gets covered with viscid 

 matter, which takes up pollen on withdrawal, and can 

 therefore effect crossing in the next flower visited. Auto- 

 matic self-pollination is excluded. 



Visitors, Herm. MuUer gives the following list. 



A. Diptera. Bombyliidae : i . Bombylius discolor 

 Mih., very common, skg. legitimately ; 2. B. major Z., 

 do. B. Hymenoptera. Apidae : 3. Anthophora 

 pilipes F. 5 and S, very common, skg. ; 4. Apis mellifica 

 Z. 5. tolerably freq., taking all the nectar from the 

 smaller flowers, and part of it from the larger ones; 

 5. Bombus agrorum F. {, very common, skg.; 6. B. 

 hortorum Z., do. ; 7. B. hypnorum Z. $, one, skg. ; 8. 

 B. lapidarius Z. 5, very common, skg. ; 9. B. pratorum 

 Z. % do. (H. M. ; Borgstette, Tecklenburg) ; 10. B. 

 terrester Z. $, skg. ; 1 1 . B. vestalis Fourcr. 5, one, skg. ; 

 12. Osmia fusca Chr. 5, persistently skg.; 13. O. rufa 

 Z. S, skg. C. Thysanoptera. 14. Thrips, freq. 



The following were recorded by the observers, and 

 for the localities stated. 



Fig. 253. Vinca minora L. 

 (after Herm. Miiller). Flower 

 after removal of half the corolla, 

 a, ovary ; i, yellow nectaries ; 

 c, style ; rf, place where a filament 

 diverges from the corolla, visible 

 externally as a depression; de^ 

 filament with its inward knee-like 

 bend; ef, introrse anther; g, 

 thickening of the style; A, disk- 

 like process of the style, covered 

 all round with sticky secretion, 

 and with a stig^atic lower edge ; 

 ky brush of hairs upon the stigmatic 

 disk, which takes up the pollen as 

 it is shed. 



Sprengel, only Thrips. Knuth (Kiel churchyard, 

 26. 4. '96), the humble-bee Bombus hortorum Z. 5, 

 occasional, skg., visiting several flowers in succession. 

 Alfken (Bremen), 2 bees i. Osmia rufa Z. 5 and $; 



2. Podalirius acervorum Z. S. Schletterer (Pola), the bee Andrena deceptoria 

 Schmiedekn. 



1861. V. major L. (Sprengel, ' Entd. Geh.,' pp. 136-7 ; Darwin, Gard. Chron., 

 London, 1861, p. 552; Herm. Muller, * Fertilisation,' p. 396; Knuth, ' Bloemenbiol. 

 Bijdragen' ; Baillon, Bull. soc. linn., Paris, i, 1882.) The flower mechanism of this 

 species agrees with that of V. minor. The corolla-tube is 15-16 mm. long, and 

 a proboscis of 11 mm. can secure all the nectar. The flowers are self-sterile. 

 Darwin was able to cause the production of good fruits by effecting artificial 

 pollination with a small brush. Baillon gives a detailed account of the flower 

 mechanism. 



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

 stated. 



Knuth, the humble-bee Bombus hortorum Z. 5, skg., repeatedly. Herm. Muller, 

 the humble-bee Bombus agrorum F. 5, skg. numerous flowers. Schletterer (Pola), 

 an Ichneumonid (Bassus laetatorius F^ and 6 bees i. Bombus argillaceus Scop., 

 skg. ; 2. B. terrester Z. ; 3. Eucera clypeata Er. ; 4. E. longicornis Z. ; 5. Poda- 

 lirius acervorum Z. ; 6. P. crinipes Sm. 



1862. V. rosea L. (=Lochnera rosea Reichb.). The flower mechanism of 

 this species is the same as that of V. minor. 



1863. V. herbacea Waldst. et Kit. The flower mechanism of this species 

 is the same as that of V. minor. 



