CRUCIFERAE 123 



the anthers of the long stamens upon the stigma, and according to Comes (' Stud. 

 s. impoU. i. ale. piante ') it is effective. Warnstorf (Verh. bot. Ver., Berlin, xxxviii, 

 1896) describes the flower as protogynous. The pollen-grains are pale yellow, 

 ellipsoidal, with reticulated ridges, about 44 /a long and 25 fx broad. 



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

 A. Diptera. (a) Bibionidae: i. Bibio hortulanusZ. jand 5, skg. (b) Syrphidae: 

 2. Ceria conopsoides Z., skg. ; 3. Eristalis arbustorum L. B. Hymenoptera. 

 (a) Apidae: 4. Andrena propinqua Schenck 1, skg. and po-cltg. ; 5. Prosopis com- 

 munis Nyl. S, skg. (b) Tenthredinidae : 6. Cephus sp. 5. 



307. B. Enicago L. — Comes says that this species is self-fertile. 

 Visitors. ^ — Schletterer observed the following bees at Pola. — 



I. Andrena flavipes Pz.; z. A. nanaX. ; 3. Halictus hscinlellus ScAencA ; 4. H. 

 morbillosus Kirchb.; 5. H. morio F. 



97. Cakile Tourn. 



Moderately large homogamous flowers, bright violet to almost white, with 

 concealed nectar. Four nectaries. 



308. C. maritima Scop. (IMacLeod, Bot. Jaarb. Dodonaea, Ghent, i, 1889; 

 Knuth, 'Bl. u. Insekt. a. d. nordfr. Ins.,' pp. 31-2, 149-50, ' Weit. Beob. ii. Bl. u. 

 Insekt. a. d. nordfr. Ins.,' p. 231, ' Bl. u. Insekt. a. Helgoland.') — The fragrant 

 flowers possess four nectaries : a larger triangular one between and outside the two 

 long stamens of each pair, and a small bilobed one internal to each short stamen. 

 The closely apposed sepals hold the claws of the petals together so as to form 

 a vertical tube 4-5 mm. long, in which nectar collects, often so abundantly as to 

 half fill it. The anthers of the long stamens project beyond the corolla, so that 

 automatic self-pollination may take place by the fall of pollen upon the stigma, 

 which is placed in the entrance of the flower and matures simultaneously. The 

 anthers of the short stamens remain enclosed in the flower, and reach the level 

 of the stigma. 



Insects are as likely to effect cross- as self-pollination. When probing for 

 nectar — as in the case of all Cruciferae — they thrust their head or proboscis between 

 the stigma and anthers so as to dust only one side of it, provided they work round 

 the flower, and do not repeat the process. If the other side of the head or proboscis 

 had previously been dusted in another flower, the stigma will be cross-pollinated. 

 If an insect thrusts its head into the flower first on one side and then on the 

 other, self-pollination will result. After several flowers have been visited by an 

 insect, both sides of its head will be dusted, and every fresh visit will effect cross- 

 pollination. 



Visitors. — I have observed the following at Kiel and in the North Frisian 

 Islands. — 



A. Coleoptera. i. Meligethes. B. Diptera. (a) Musa'dae: 2. Aricia albo- 

 lineata Fall. ; 3. Musca domestica Z. ; 4. Onesia sepulcralis Mg. ; 5. Scatophaga 

 merdaria Z". ; 6. S. stercoraria Z. ; all po-dvg. (U) Syrphidae: 7. Eristalis arbustorum 

 Z.; 8. E. pertinax 6V(7/.; 9. E. sp.; 10. E. tenax Z.; 11. Platycheirus podagratus Z^/"/. 

 12. Rhingia campestris Mg.; 13. Syrphus arcuatus Z'a//.; 14. S. umbellatarum /'. 

 15. Tropidia milesiformis Fall., all skg. and po-dvg. C. Hymenoptera. (a) Apidae 



