CRUCIFERAE 107 



Small insects collecting or devouring pollen can only obtain it from the anthers 

 fof the long stamens, which project somewhat from the flower, and in doing so 

 they may effect self-pollination by shaking down pollen upon the stigma. Failing 

 insect-visits, autogamy results automatically from the fall of pollen. 



Visitors. In the Garden of the Ober Realschule at Kiel I have observed 



nectar-skg. butterflies Vanessa urticae Z., and Pieris brassicae Z. J. These 



regularly fly from flower to flower and thus effect cross-pollination. I have further 



seen, skg., Anthophora pilipes F. J, which has a longer proboscis than any other 



of our spring bees ; and also Bombus lapidarius Z. 5 and 5. Several honey-bees 



made persistent efforts to suck nectar, and as they visited numerous flowers suc- 



. cessively I was able to detect the sucking movements, so that they evidently succeeded 



in reaching the nectar with their proboscis (6 mm. long), and effected cross-pollination 



I in the same way as Lepidoptera. A small pollen-collecting bee Andrena gwynana 



! K. 5 occasionally effected self-pollination, as did a pollen-devouring hover-fly 



: Syritta pipiens Z. 



251. L. rediviva L. 



Visitors. Loew saw the honey-bee sucking the flowers of this species in the 

 Berlin Botanic Garden. 



75. Schievereckia Andr. 

 Flowers with half-concealed nectar. Four nectaries. 



252. S. podolica Andrz. (Kerner, 'Nat. Hist. PI./ Eng. Ed. 1, II, pp. 1 75. 339.) 

 There is a nectary on either side the base of each short stamen. Self-pollination 

 is at first precluded by protogyny. Even after the dehiscence of the anthers it is 

 at first prevented, for the stamens remain at a distance from the stigma. Towards 

 the end of anthesis autogamy takes place, as the stamens bend towards the middle of 

 the flower. 



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



A. Coleoptera. Nitidulidae \ 1. Meligethes aeneus F., nect-lkg. B. Diptera. 

 Syrphidae : 2. Eristalis aeneus Scop., po-dvg. C. Hymenoptera. Apidae : 3. Andrena 

 parvula K. 5, skg. and po-cltg. ; 4. Apis mellifica Z. jj|, skg. ; 5. Halictus nitidiusculus 

 K. 5, skg. and po-cltg. 



76. Petrocallis R. Br. 



Rose-coloured homogamous flowers, with half-concealed nectar. Four nectaries. 



253. P. pyrenaica R. Br. (Schulz, 'Beitrage,' II, p. 16.) There is a richly 

 secreting nectary on either side the base of each short stamen. At the beginning of 

 anthesis the anthers of these stamens are at the same level as the stigma which 

 is already mature but the filaments curve outwards at their bases, so that there 

 is no contact. The filaments of the long stamens are parallel for half their length, 

 and then bend outwards. Their anthers are curved downwards, and lie almost 

 immediately above those of the short stamens. They cannot easily effect automatic 

 self-pollination. 



Visitors. Schulz in the Tyrol saw numerous flies and Lepidoptera, which 

 in many cases would effect self- as well as cross-pollination. 



