576 AN GIOSPERM AE DICOTYLEDON ES 



Eng. Ed. i, II.) In this species the ray-florets are female, nectarless, with a more 

 or less reduced corolla -limb. The disk -florets are hermaphrodite and distinctly 

 protandrous, so that, according to Hermann Muller, automatic self-pollination is 

 completely excluded or almost so. Kerner states that geitonogamy is possible, 

 by curving outwards of the pollen-covered stylar branches. 



Visitors. Ricca observed flies; Herm. Muller chiefly Lepidoptera (28), also 

 5 flies and a humble-bee. 



416. Tussilago L. 



Monoecious. Disk-florets male, with vestigial pistils; the ray-florets female; 

 multiseriate, ligulate. The stylar branches of the female florets possess stigmatic 

 papillae on their inner surfaces, and (useless) sweeping-hairs externally and apically. 

 In male flowers these branches remain united almost to their tips; externally and 

 above they are covered with short sweeping-hairs. 



1320. T. Farfara L. (Sprengel, 'Entd. Geh.,' pp. 374-6; Herm. Muller, 

 'Fertilisation,' pp. 333-4, ' Alpenblumen,' pp. 454-5; Knuth, ' Bl. u. Insekt. a. d. 

 nordfr. Ins./ pp. 85, 157 ; Kerner, 'Nat. Hist. PI., 'Eng. Ed. 1, II.) In this species 

 30-40 golden-yellow purely male disk-florets are surrounded by about 300 purely 

 female ray-florets, similarly coloured, and multiseriate. The head expands in the 

 sunshine into a surface 20-25 mm. broad, and closes at night or during dull weather. 

 The male florets possess an ovary containing a vestigial ovule, and there is a yellow 

 nectar-ring at the base of the style. The pollen is pushed out of the anther-cylinder 

 by the sweeping-hairs. 



The nectarless female ray-florets possess a corolla-tube 3 mm. long, with a 

 narrow linear limb 6-8 mm. in length, and directed outwards. The style projects 

 2-3 mm. from the floret, and is divided at its end into two stylar branches about 

 \ mm. long, and papillose internally. The stigmas of the ray-florets become 

 receptive a considerable time before the pollen is swept out of the male ones. 

 There is therefore constant crossing of different stocks when insect-visits are 

 sufficiently numerous. Owing to the unisexual character of the florets, automatic 

 self-pollination is necessarily excluded. Kerner states that automatic geitonogamy 

 takes place when the ligulate ray-florets close about 5-6 p.m. In doing so, they 

 bend over the disk-florets in such a way that they touch the pollen-masses which 

 have been swept out of the anther-cylinders of the male florets. The pollen-grains 

 adhere to the ligulate florets, and when the head opens again next morning some 

 of them slide down to the respective stigmas. Warnstorf describes the pollen-grains 

 as golden-yellow in colour, rounded to ellipsoidal, densely spinose, about 44/1 long 

 and 37 fi broad. 



According to Burkill (' Fertlsn. of Spring Fls.'), the heads that blossom on the 

 cliffs of the Yorkshire coast contain about 200 to 300 female florets and about 

 40 male ones, and are 20-36 mm. in diameter ; while those on the lower slopes 

 of the shore only attain a diameter of about 15 mm. During anthesis the corolla- 

 tubes of the disk-florets lengthen about 1 mm.; the ligulate florets simultaneously 

 increase in size, and their receptacles broaden. The head, therefore, becomes 

 somewhat more conspicuous as it passes from the first to the last stage. As 



