CRUCIFERAE 97 



between the pairs of long stamens, sometimes — says Miiller — in such quantity as to 

 touch the sepals outside these. Jordan states, however, that the anterior and posterior 

 nectaries are not functional. The two short stamens are usually not as long as the 

 pistil, though this is sometimes the case : they curve outwards away from it, and in 

 doing so turn the pollen-covered sides of their anthers inwards. The four long 

 stamens remain in the middle of the flower, but make a quarter- or half-turn, so that 

 the pollen-covered sides of their anthers are turned towards the adjacent short 

 stamens, or even completely outwards. I found the wild cabbage of Helgoland 

 to agree with this description of Hermann Miiller's. Insects when probing for 

 the nectar secreted by the inner nectaries chiefly effect cross-pollination. The 

 nectar of the other glands can be got at without touching the stigma, so that these 

 are probably useless for pollination, as the observations of Jordan appear to indicate 

 (vide supra). Should insects fail to visit the flowers, the upper parts of the long 

 stamens usually curve so far towards the stigma as to touch it, thus effecting 

 automatic self-pollination. Lund and Kjaerskou (Justs Bot. Jahresber., Leipzig, xiii, 

 (1885) 1887, p. 753) say that this is effective, but the numerous fruits which result 

 do not usually contain so many seeds as those produced by crossing. 



Visitors. — The honey-bee here takes a prominent place. Besides this, I have 

 observed — in Helgoland — another bee — Andrena carbonaria Z., skg., corresponding 

 to the flower in size, and — mostly in the same island — the white cabbage-butterfly, 

 Pieris brassicae L. On the North Frisian Islands I further noticed various po-dvg. 

 and skg. Syrphidae — Helophilus, Eristalis, Syrphus, Rhingia — and also a humble-bee, 

 Bombus terrester L., skg. A small beetle (Meligethes) is everywhere found po-dvg. 

 and gnawing the petals, usually without benefit to the flower. 



Hermann Miiller (H. M.) and Buddeberg (Budd.) have observed the 

 following.- — 



A. Coleoptera. Nitidulidae: i. Meligethes, very freq., po-dvg. or gnawing 

 the flower (H. M.). B. Hymenoptera. (a) Apidae : 2. Andrena fulvescens Sm. 5 

 po-cltg. (Budd.) ; 3. A. fulvicrus K 5, po-cltg. (H. M.) ; 4. A. nana X. 5, skg. (H. M.) 

 5. A. gwynana K. 5, skg. and po-cltg. (M. M.); 6. A. nigroaenea IT. j, skg. (H. M.) 

 7. Apis meUifica Z. 5, skg. and po-cltg. (H. M.) ; 8. Halictus cylindricus A'. 5 (H. M.) 

 9. H. morio I^. j, po-cltg. and skg. (Budd.); 10. Osmia rufa Z. J, skg. (Budd.). 

 C. Thysanoptera. 11. Thrips, freq. (H. M.). 



Alfken and Hoppner (H.) noticed the following at Bremen. — Apidae: i. Andrena 

 albicans Miill. 5, not infrequent; 2. A. humilis Imh. S (H.); 3. A. argentata K. 5, 

 rare; 4. A. carbonaria Z. 5, infrequent; 5. A. convexiuscula K. $, infrequent; 6. A. 

 nigroaenea .AT. j, not infrequent; 7. A. propinqua^c^OTf^j (H.) ; 8. Bombus agrorum 

 F. 5, infrequent ; 9. B. derhamellus K. 5, infrequent; 10. B. sylvarum Z. 5, infrequent ; 

 II. Halictus calceatus Scop. 5, very freq.; 12. H. flavipes F. j, freq.; 13. H. levis 

 K. 5, infrequent; 14. H. minutus K. $, infrequent; 15. H. nitidiusculus K. 5, freq.; 

 16. H. punctulatus K. j, freq. ; 17. H. rubicundus Chr. j, freq. ; 18. H. sexnotatulus 

 Nyl. 5, rare; 19. Nomada succincta Pz. 5 and S, skg.; 20. Osmia rufa Z. 5 and 

 J, not infrequent; 21. Podalirius retusus Z. 5 and J, infrequent. 



Leege saw the following Apidae on Juist. — i. Colletes cunicularis Z.; 2. Osmia 

 maritima Friese S, freq., skg. 



Loew observed the following in the Berlin Botanic Garden. — Hymenoptera. 

 Apidae: i. Andrena carbonaria Z. S, skg. ; 2. A. extricata 6'»z. 5, po-cltg. ; 3. Bombus 

 agrorum F. $, skg. and po-cltg. ; 4. B. lapidarius Z. $, skg. ; 5. B. terrester Z. } and 

 5, skg. and po-cltg. ; Osmia rufa Z. S, skg. 



