io8 



ANGIOSPERMAE—DICOTYLEDONES 



77. Erophila DC. 



Small white flowers, homogamous to slightly protogynous, with half-concealed 



nectar. Four nectaries. 



254. E. vema E. Meyer ( 



Draba verna Z.). (Herm. Miiller, 'Fertilisation,' 

 p. 105, 'Weit. Beob.,' I, p. 327; Hildebrand, 'Die Geschlechtsvert. b. d. Pfl.,' p. 70; 

 Kerner, 'Nat. Hist. Pi.,' Eng. Ed. i, II; Kirchner, 'Flora v. Stuttgart,' p. 305; 

 Knuth, ' Bl. u. Insekt. a. d. nordfr. Ins.,' p. 28.) — The four small green nectaries are 

 situated on either side the base of each short stamen. The pollen-covered sides of 

 the four long stamens lie close to the stigma — which matures simultaneously — and as 

 they discharge a cloud of pollen when even slightly shaken automatic self-pollination 

 is inevitable. Hildebrand's experiments prove this to be effective. The anthers of 

 the short stamens are lower than the stigma, and serve for cross-pollination. While 

 Miiller describes the flowers as homogamous, Kerner says that they are protogynous 

 at the beginning of the first day of anthesis, though later on that day the anthers 

 dehisce and automatic self-pollination is effected by bending of the stamens towards 



the middle of the flower. 

 Kerner also states that 

 the petals increase great- 

 ly in size during anthesis. 

 The flowers open about 

 nine in the morning, and 

 close about six o'clock in 

 the evening. 



Jordan distinguishes 

 between short-fruited 

 and long-fruited forms 

 or varieties of Erophila. 

 The former have the 

 structure just described; 

 in the latter the stigma 

 projects beyond the an- 

 thers, and it therefore 

 frequently happens that 

 no fruits are set. 

 Visitors. — Owing to the smallness of the flowers insect-visits are rare. At Kiel 

 I only saw the honey-bee, skg. and po-cltg. Hermann Miiller — in Westphalia — 

 besides the honey-bee, observed 2 small short-tongued bees — Andrena parvula K. 5, 

 and Halictus sp., skg. — and also a few po-dvg. Muscidae — Anthomyia sp., Hylemyia 

 cinerella Mg., and Sarcophaga carnaria L. 



Alfken observed the following at Bremen. — 



A. Hymenoptera. Apidae: i. Andrena parvula A^. 5, po-cltg. and skg, 

 S skg.; 2. Apis mellifica Z. ^, po-cltg. and skg.; 3. Bombus terrester Z. 5, skg. 

 4. Halictus calceatus Scop. 5, skg. and po-cltg. ; 5. H. morio F. 5, skg. and po-cltg. 

 6. Halictus nitidiusculus .A!". 5, skg. and po-cltg. B. Diptera. Muscidae: 7. Musca 

 domestica Z. J, skg. 



Fig. 32. Draba aisoides, L. (after Herm. Miiller). A. 

 above. B Flower after removal of calyx and corolla, 

 the bases of the filaments. /;, drops of nectar ; «, nectary 

 /, long stamens ( x 7). 



Flower seen from 

 C. Nectary and 

 k^ short stamen ; 



