8o 



ANGIOSPERMAEDICOTYLEDONES 



between the stamens, and are confluent so as to form a ring. The anthers of the jj 

 four long stamens reach the level of the stigma, those of the two short ones being \ 

 somewhat lower. In sunny weather the stamens spread out somewhat, and the |i 

 anthers dehisce introrsely, so that insects probing for nectar necessarily touch 

 the stigma and the pollen with different sides of their head. They therefore effect 

 either cross- or self-pollination. In rainy weather the flowers only half open, so 

 that the anthers of the long stamens come into contact with the stigma which 

 is at the same level and automatic self-pollination results. 



Warnstorf (Verh. bot. ver., Berlin, xxxviii, 1896) says that the flowers are 

 slightly protogynous. At the time of flowering the stamens project beyond the 

 stigma, over which their anthers incline. During dehiscence these bend outwards 

 at right angles, so that the open loculi with the pollen are turned upwards away 

 from the stigma. Self-pollination is thus rendered difficult and cross-pollination 

 favoured. Between the filaments at the base of the ovary are six small dark-green 

 nectaries. The pollen-grains are yellow, ellipsoidal, densely tuberculated. They 

 are up to 44 fi long and 25-32 //, broad. 



Visitors. The following were observed by Hermann Miiller (H. M.) and 

 myself (Kn.). 



A. Coleoptera. Nitidulidae: 1. Meligethes nect-skg. and po-dvg. (H. M.). 

 B. Diptera. (a) Empidae: 2. Empis livida L., skg. (H. M.). (b) Muscidae: 3. 

 Calobata cothurnata Pz. (H. M.); 4. Sp. of Lucilia po-dvg. (H. M.). (c) Syrphidae: 

 5. Eristalis arbustorum Z., skg. and po-dvg. (Kn., H. M.) ; 6. Rhingia rostrata Z., 

 skg. (H. M.) ; 7. Syritta pipiens Z., skg. (H. M.). C. Hymenoptera. Apidae : 

 8. Apis mellifica Z. 5, skg. (Kn., H. M.). (b) Pteromalidae : 9. Pteromalids nect-skg. 

 (H. M.). (c) Tenthredinidae : (a) Allantus arcuatus ForsL, skg. (H. M.). 



MacLeod in Flanders observed Apis, 9 short-tongued bees, a wood-wasp, 

 5 hover-flies, and 4 other flies (Bot. Jaarb. Dodonaea, Ghent, vi, 1894, p. 198). 



175. N. sylvestre R. Br. (Herm. Miiller, 

 ' Fertilisation,' pp. 100-1, ' Weir. Beob.,' i, p. 324.) 

 The flower mechanism agrees with that of the last 

 species, but there are four, fleshy, non-confluent 

 nectaries. 



Hermann Miiller (H. M.) and Buddeberg 

 (Budd.) observed the following. 



A. Diptera. (a) Bombyliidae : 1. Anthrax 

 hottentotta Z., skg. (Budd.). (b) Empidae: 2. Empis 

 livida Z., skg. (H. M.). (c) Syrphidae: 3. Chryso- 

 gaster macquarti Zoew, skg. (H. M.) ; 4. Eristalis 

 arbustorum Z., skg. (H. M.) ; 5. Syritta pipiens Z., 

 and 6. Syrphus sp., both skg. and po-dvg. (H. M.). 

 B. Hymenoptera. (a) Apidae-. 7. Andrena labiata 

 Schenck <j>, po-cltg. (H. M.) ; 8. Apis mellifica Z. $, 

 freq., po-cltg. (H. M.) ; 9. Halictus nitidiusculus K. $, J 

 skg. (H. M.). (b) Sphegidae: 10. Crabro wesmaeli 

 v. d. Z., skg. (H. M.) ; 11. Tiphia minuta v. d. L., 

 ditto (H. M.). 



Alfken noticed the following Apidae at Bremen. Halictus nitidiusculus K. 5, 

 and Andrena albicans Mull. 5. 



Fig. 28. Nasturtium sylvestre, R. Br. 

 (after Herm. Miiller). Flower seen from 

 above ; in the centre is the stigma cover- 

 ing the ovary; around it are the four 

 larger () and two smaller (') nectar- 

 drops ; to right and left are the two short 

 stamens (a'), anteriorly and posteriorly 

 the two pairs of long stamens (a). In all 

 the stamens the pollen-covered surface of 

 the anthers is visible, turned towards the 

 stigma. The filaments are all consider- 

 ably foreshortened. ,?, sepal ; /, petal. 



