CRASSULACEAE 



433 



the Riesengebirge, according to Schulz, and in the male and female flowers there 

 are vestiges of the other sex-organs. Axell also found only dioecious plants, as 

 did Lindman on the Dovrefjeld. Ricca, in the Alps, observed protandrous herma- 

 phrodite flowers, and so did Warming in Greenland, but the latter noticed also 

 cases of trioecism. 



Ekstam says that in Nova Zemlia the flowers smell like honey, and secrete 

 abundant nectar. 



Visitors. Small flies were noticed by Ekstam in Nova Zemlia. Ricca observed 

 flies and ants in the Alps. In Dumfriesshire, an Empid and a Muscid were recorded 

 (Scott-Elliot, ' Flora of Dumfriesshire,' p. 68). 



281. Sedum L. 



Flowers protogynous, or homogamous to markedly protandrous; with half- 

 concealed nectar, secreted basally between petals and stamens. 



995. S. acre L. (Herm. Mtiller, 'Fertilisation,' pp. 251-3; MacLeod, Bot. 

 Jaarb. Dodonaea, Ghent, vi, 1894, p. 289; Knuth, 'BL u. Insekt. a. d. nordfr. Ins.,' 

 pp. 74, 154, 'Weit. Beob. 

 u. Bl. u. Insekt. a. d. nordfr. 

 Ins.,' p. 234.) The flowers 

 of this species are bright 

 yellow in colour, and the 

 five outer stamens super- 

 posed to the sepals are 

 the first to mature. They 

 direct their filaments (about 

 5 mm. long) obliquely up- 

 wards. When they have 

 shed their pollen they bend 

 back towards the petals, 

 while the five inner anthers 

 dehisce, and assume the 

 position of the first five. 

 The small terminal stigmas 

 of the five carpels do not 

 mature till the inner anthers 

 have shed all their pollen. I observed this marked protandry, which completely 

 prevents self-pollination, in the island of Fohr. 



Elsewhere the flowers are not so distinctly protandrous. Hermann Miiller states 

 that in Westphalia the stigmas mature before the five inner stamens have finished 

 shedding their pollen, so that automatic self-pollination is possible if insect- 

 visits fail. 



Visitors. I observed the following in Schleswig-Holstein, all skg. 



A. Diptera. (a) Muscidae: 1 . Anthomyia sp. ; 2. Calliphora erythrocephala 

 Mg. ; 3. Lucilia sp. ; 4. Nemotelus uliginosus Z. 5 ; 5. Spilogaster carbonella Zett. 

 (/>) Syrphidae : 6. Eristalis tenax Z. ; 7. Melithreptus taeniatus Mg. ; 8. Syritta pipiens 



FIG. 140. Sedum acre, L. (after Herm. Miiller). (i) Flower in the 

 first stage, seen obliquely from above, a 1 and a 2 , outer and inner 

 stamens ; w, nectary ; ov, ovary ; p, petal ; s, sepal. (2) Tip of a style 

 in the first stage. (3) The same in the second stage, after all the anthers 

 have dehisced. 



