324 ANGIOSPERMAEDICOTYLEDONES 



In these circumstances it flies straight to the spikes, goes once round the zone 

 containing opening flowers, and brushes its legs over the projecting anthers. It is 

 thus able, after the loosely-placed pollen has been dispersed by the wind, to obtain 

 still further supplies. Honey-bees vary individually in their treatment of these 

 anemophilous flowers. Thus Hermann Miiller observed one which hovered buzzing 

 and with outstretched proboscis in front of the flowering spike, but gripped it firmly 

 with its feet each time when collecting pollen (' Weit. Beob.,' Ill, pp. 63-4). 



Herm. Miiller gives the following list. 



A. Diptera. Syrphidac. i. Melanostoma mellina Z., very common, po-dvg. ; 

 2. Syrphus ribesii Z., repeatedly, po-dvg. ; 3. Volucella pellucens Z., po-dvg. 

 B. Hymencptera. Apidac. 4. Apis mellifica Z. 5. very common, po-cltg. ; 

 5. Bombus pratorum Z. 5, po-cltg. ; 6. Halictus sp., working at the anthers. 



The following were recorded by the observers, and for the localities stated. 



Knuth (Rom), the po-dvg. hover-fly Helophilus pendulus Z. : (Friederichsroda, 

 Thuringia, July, '94), the humble-bee Bombus terrester Z. 5, po-cltg. MacLeod 

 (Flanders), the hover-fly Melanostoma mellina Z., po-dvg. (Bot. Jaarb. Dodonaea, 

 Ghent, v, 1893, p. 371). Scott-Elliot (Dumfriesshire), the honey-bee, a humble-bee, 

 a hover-fly (rare), and a Lepidopterid (' Flora of Dumfriesshire,' p. 334). 



2394. P. media L. (Darwin, ' Forms of Flowers,' p. 307 ; Ludwig, Zs. Ges. 

 Natw., Berlin, Hi, 1879, pp. 441-9; Herm. Miiller, 'Fertilisation,' pp. 506-8, 

 ' Alpenblumen,' p. 357, 'Weit. Beob.,' Ill, p. 64; Knuth, ' BlUtenbesucher,' pp. 9-10, 

 'Bliitenbiol. Herbstbeob.,' ' Bloemenbiol. Bijdragen'; Kirchner, ' Flora v. Stuttgart,' 

 pp. 647-83 Schulz, 'Beitrage,' I, pp. 92-3, II, p. 198.) This species exhibits 

 gynodioecism, gynomonoecism, andromonoecism, and androdioecism with proto- 

 gynous hermaphrodite flowers. We have here a transition between anemophily and 

 entomophily, to express which I have employed the term wind flowers ' (cf. Vol. I, 

 p. 69). The violet colour of the stamens and the delicate odour of the whorled 

 flowers attract numerous visitors, including humble- and honey-bees. Hermann 

 Miiller tried to distinguish between two forms, one predominantly anemophilous, the 

 other mainly entomophilous. 



(a) var. anemophila Knuth. Long scapes, with spikes of about 4 cm. elongating 

 to 7-8 cm. as they fade ; the feebly curved filaments are white and project 7-9 mm. 

 out of the flower ; pollen powdery as in (3), but slightly less adhesive. Stigmas long ; 

 corolla-lobes pointed and spreading. 



{b) var. entomophila Knuth. Shorter scapes of about 15 cm.; the stiff" filaments 

 shorter and reddish ; pollen more adhesive than that of (a), but the grains here also 

 are so smooth and dry that they are easily removed by wind. Ekstam states that in 

 the Swedish Highlands this plants possesses a pleasant odour and reddish spikes 

 as attractions, thus, in his opinion, deceiving insects such as humble-bees and 

 flies. Stigmas project only slightly; corolla-lobes rounded and directed obliquely 

 upwards. 



Both forms are protogynous, but less strongly so than P. lanceolata, for the 

 stigma is still receptive when the anthers dehisce. Schulz says that the degree of 

 protogyny varies, and that the flowers may even be homogamous. 



Gynodioecism was observed by Darwin in England, and by Ludwig in Thuringia. 



