CRUCIFERAE 105 



245. A, alpestre L. (Kirchner, 'Beitrage,' pp. 25-6.) — The homogamous 

 flowers smell of honey, and those growing on the ' yellow wall ' at Zermatt are of 

 a golden-yellow colour. Their diameter is 3-4 mm. The four nectaries are on 

 either side the bases of the two short stamens. The anthers of the four long stamens 

 are at the same level as the stigma — which matures simultaneously — and both 

 project about i mm. above the entrance to the flower, in which the anthers of 

 the two short stamens are situated. The anthers dehisce introrsely and remain 

 facing inwards, but they are so far removed from the stigma that automatic 

 self-pollination is not completely assured. 



246. A. saxatile L. — 



Visitors. — Loew observed the Syrphid Eristalis sepulcralis Z., skg., in the 

 Berlin Botanic Garden. 



72. Aubrietia Adans. 



247. A. Columnae Guss. — 



Visitors. — Loew saw the honey-bee skg. in the Berlin Botanic Garden. 



248. A. spathulata DC. — 



Visitors. — As A. Columnae. 



73. Berteroa DC. 



White homogamous flowers with half-concealed nectar. Four nectaries. 



249. B. incana DC. (Schulz, ' Beitrage,' I, p. 4 ; Kirchner, ' Flora v. Stuttgart,' 

 p. 304; MacLeod, Bot. Jaarb. Dodonaea, Ghent, vi, 1894, p. 209; Warnstorf, 

 Verb. bot. Ver., Berlin, xxxviii, 1896 ; Knuth, ' Bliitenbiol. Herbstbeob.,' 'Bloemen- 

 biol. Bijdragen.') — There are four nectaries, one internal to either side the base 

 of each short stamen. The anthers of the long stamens project a little beyond 

 the stigma, and turn towards the anthers of the short stamens as soon as the flower 

 opens. The long stamens reach the level of the stigma, but their filaments are 

 bent in such a way as to remove them tolerably far from it. As, however, the 

 anthers of these stamens are usually slightly incurved at the tip, automatic self- 

 pollination is easily possible. The open passage to the secretion above each nectary 

 is narrowed by the tooth-like process of a short stamen, so that when the proboscis 

 of an insect is introduced it must be inserted between a short stamen and the 

 adjacent long one, which explains the rotation of the long stamens at the entrance 

 of the flower. 



Warnstorf says that the flowers are protogynous, and that the stigma is already 

 mature in the half-open blossom, the long stamens being at about this stage much 

 shorter than the style, and with unripe anthers. When the petals expand these 

 stamens elongate and project a little beyond the stigma, so that autogamy can readily 

 take place. The pollen-grains are yellow, ellipsoidal, finely tuberculated, about 

 35 /A long and 15 /^ broad. 



Visitors. — On garden plants at Kiel I observed the following skg. hover-flies. — 

 Eristalis arbustorum Z., E. nemorum L., Rhingia rostrata Z., Syritta pipiens Z., and 

 Syrphus ribesii Z.; salo a butterfly^Vanessa io. Z. Warnstorf noticed bees at 

 Ruppin ; and Alfken saw the bee Halictus brevicornis Schenck 5, skg., at Bremen. 



