178 ANGIOSPERMAE DICOTYLEDON ES 



(Batalin, Bot. Ztg., Leipzig, xxviii, 1870). During unfavourable weather the flowers 

 remain closed, and self-pollination' takes place. MacLeod observed (Bot. Centralbl., 

 Cassel, xxix, 1887) female as well as hermaphrodite flowers on the dunes of the 

 Flemish coast. Female stocks were also noticed by Warming in Denmark. 



Warnstorf (Verh. bot. Ver., Berlin, xxxviii, 1896) observed gynodioecism and 

 imperfect gynomonoecism at Ruppin. He distinguished (1) larger hermaphrodite 

 flowers of 10 mm. diameter, frequently with more or less reduced anthers or stamens: 

 and (2) smaller flowers of only 5-6 mm. diameter, and female by abortion of all the 

 stamens. The hermaphrodite flowers are protandrous. The first stamens to mature 

 are the outer ones, which have nectaries at their bases. These incline over the 

 still apposed stigmatic branches. The inner stamens ripen subsequently. Nectar is 

 abundantly secreted. 



Visitors. Hermann Miiller (' Alpenblumen,' p. 183) observed one of the Bom- 

 byliidae Anthrax sp. in the Alps. 



443. S. subulata Torr. et Gray. Garden plants were found by Warming to 

 be sometimes protogynous, sometimes slightly protandrous. 



127. Spergula L. 



Flowers white, usually homogamous, rarely protogynous, with half-concealed 

 nectar, secreted by nectaries situated as usual. 



444. S. arvensis L. (Herm. Miiller, 'Weit. Beob./ II, p. 225; Kerner, 'Nat. 

 Hist. Pl./Eng. Ed. 1, II; Schulz, ' Beitrage,' I, pp. 15-16; Kirchner, 'Flora v. Stuttgart,' 

 p. 232 ; Knuth, 'Bl. u. Insekt. a. d. nordfr. Ins.,' p. 43, ' Bloemenbiol. Bijdragen'.) 

 The white homogamous flowers of this species open widely in the sun, and secrete 

 nectar near the bases of the stamens. The filaments are meanwhile curved outwards to 

 such an extent that insects in quest of nectar touch the anthers with one side of their 

 body, and the stigma with the other, so that cross-pollination is promoted. During 

 unfavourable weather the flowers remain closed, and self-pollination takes place. 

 Further according to Kerner automatic self-pollination occurs towards the end of 

 anthesis, when the flowers are beginning to close. The same writer states that they 

 remain closed from 10 a.m. till 4 p.m. According to Schulz, female flowers fre- 

 quently occur, and over 50 % of them may be gynomonoecious in a given 

 locality, while gynodioecism is rare. Schulz also says that the number of stamens 

 varies, for some of them are often more or less vestigial. Normal and abnormal 

 flowers are sometimes associated on the same stock, or may occur on different ones. 



Visitors. Hermann Miiller (H. M.) in Westphalia, and myself (Kn.) in 

 Schleswig-Holstein, have observed the following. 



A. Diptera. (a) Muscidae: 1. Lucilia sp., skg. (H. M.). (b) Syrphidae: 

 2. Eristalis arbustorum Z., skg. and po-dvg. (H. M.); 3. E. tenax Z., ditto (Kn.); 

 4. Helophilus pendulus Z., ditto (H. M.); 5. Melanostoma ambigua Fall., ditto 

 (H. M.); 6. Melithreptus menthastri Z., ditto (H. M.); 7. M. strigatus Staeg., 

 ditto (H. M.); 8. Syritta pipiens L., ditto (H. M., Kn.); 9. Syrphus balteatus Deg., 

 ditto (H. M., Kn.); 10. S. corollae F., ditto (H. M.); 11. S. ribesii Z., ditto (H. M., 

 Kn.). B. Hymenoptera. (a) Apidae: 12. Andrena albicrus Mull. 5, po-cltg. 

 (H. M.); 13. A. convexiuscula K. J, skg. (H. M.); 14. Apis mellificaZ., skg. (Kn.); 

 15. Halictus malachurus K. 5, skg. and po-dvg. (H. M.). (b) Sphegidae: 16. Crabro 

 wesmae'li v.d. L. 5, skg. (H. M.). 



