CRUCIFERAE 109 



MacLeod saw 2 Muscids in Flanders (Bot. Jaarb. Dodonaea, Ghent, vi, 1894, 

 p. 210), and Burkill (' Fertlsn. of spring fls.') noticed — on the Yorkshire coast — 

 a minute short-tongued Dipterid, skg. nectar. In Dumfriesshire (Scott-Elliot, ' Flora 

 of Dumfriesshire, p. 17) a beetle and 2 flies have been recorded. 



78. Draba L. 



Small white or yellow flowers, homogamous or protogynous, with half-concealed 

 to completely-concealed nectar. 



255. D. aizoides L. (Hildebrand, 'Vergleich. Untersuch. ii. d. Saftdr. d. 

 Cruciferen,' p. 13; Herm. Muller, 'Alpenblumen,' pp. 145-6; Kerner, 'Nat. Hist. 

 PI.,' Eng. Ed. I, II.) — The flowers are at first golden yellow, subsequently whitish. 

 In the first (female) stage the stigma projects beyond the still unripe stamens. The 

 anthers only dehisce when these have grown so far that the long ones reach the level 

 of the stigma towards which they may then incline, effecting automatic self-pollination. 

 In sunny weather, however, the stamens spread out, rendering the nectar visible, and 

 cross-pollination is effected by insect visitors. 



Visitors. — Hermann Muller observed flies — 7 Muscidae and 6 Syrphidae — 

 10 Lepidoptera, and a beetle in the Alps. 



256. D. Zahlbruckneri Host. (Kirchner, 'Beitrage,' p. 26.) — Self-pollination 

 is possible in a late stage of anthesis of the golden yellow protogynous flowers, as 

 a result of the fall of pollen. On either side of each short stamen there is a small 

 functional nectary. 



257. D. Wahlenbergii Hartm. (Herm. Muller, 'Alpenblumen,' p. 146; 

 Warming, ' Biol. Optegn. om Gronl. PI.') — This species is homogamous. Failing 

 insect-visits, self-pollination regularly takes place. 



In Greenland it produces ripe fruits (Abromeit, ' Bot. Ergeb. d. Drygalski's 

 Gronlands-Exped.,' pp. 25-6). 



258. D. Thomasii Koch. — 



Visitors. — Hermann Muller — in the Alps— observed chiefly flies — 3 Muscidae 

 and a Syrphid. 



259. D. frigida Sauter. — Flowers homogamous and capable of self-pollination. 

 Visitors. — Hermann Muller observed a Muscid ('Alpenblumen,' p. 147). 



260. D. incana L. — -Warming says that in Greenland this species is homogamous 

 and capable of automatic self-pollination. According to the same authority this is also 

 true in the same country for. — 



261. D. nivalis Liljebl., 262. D. corymbosa R. Br., 263. D. arctica J. Vahl, 

 and 264. D. Hirta L., with its variety Hartm., while its variety leiocarpa Lindbl. is 

 not so easily automatically self-pollinated. Abromeit (op. cit., pp. 25-6) states that 

 D. arctica and D. hirta produce ripe fruits in Greenland, where D. nivalis with its 

 small white flowers ascends to a height of 3,000 feet above sea-level (op. cit., 

 pp. 24-5). 



