556 ANGIOSPERMAE—DICOTYLEDONES 



LIV. ORDER DIPS ACE AE DC. 



Literature. — Knuth, ' Grundriss d. Bliitenbiol.,' pp. 63-4. 



The small flowers are united into large capitula, so that they are very con- 

 spicuous and receive numerous insect-visits. Cross-pollination is secured in our 

 native species by marked protandry of the hermaphrodite flowers. Nectar is secreted 

 by the surface of the ovary, and is concealed in the base of the corolla-tube. All the 

 species consequently belong to flower class S. Gynodioecism is common. 



406. Morina Toum. 



Slightly protogynous flowers, which open in the twilight, and are therefore 

 adapted to the visits of crepuscular and nocturnal Lepidoptera. 



1288. M. persica L. (Kemer, 'Nat. Hist. PI.,' Eng. Ed. i, II, p. 351.) — Kemer 

 states that in this species protogyny only lasts for half-an-hoiK, but this is sufiicient to 

 permit of crossing taking place at first. As soon as the limb of the corolla expands, 

 the thick swollen stigma becomes visible just above the passage leading to the nectar, 

 its receptive surface facing downwards. The two anthers behind it are still immature, 

 so that the proboscis of an insect, if already dusted with pollen, must effect crossing 

 while probing for nectar. 



1289. M. elegans Fisch. et Avd-Lall. (=M. longifolia Wall.). (Hildebrand, 

 Bot. Ztg., Leipzig, xxvii, 1869, pp. 488-91.) — HUdebrand describes the flowers of 

 this species as homogamous, but the stigma projects beyond the anthers, so that 

 insects usually touch it first, cross-pollination being thus favoured. The stigma 

 subsequently bends downwards and comes into contact with the anthers, and 

 automatic self-pollination may therefore take place at this stage. 



407. Dipsacus L. 



Flowers whitish or lilac in colour ; markedly protandrous ; aggregated into 

 ovoid or globular heads. Spinescent bracts prevent insect visitors from creeping 

 over the inflorescences, and these touch the anthers and stigmas with their heads, 

 not their feet. 



1290. D. sylvestris Mill. (Herm. Miiller, 'Fertilisation,' pp. 308-9, 'Weit. 

 Beob.,' Ill, p. 76; Heinsius, Bot. Jaarb. Dodonaea, Ghent, iv, 1892, p. 8i ; Knuth, 

 ' Bloemenbiol. Bijdragen'; Loew, ' Blutenbiol. Floristik,' p. 390.) — Hermann MuUer 

 describes the corolla-tube of the lilac flowers of this species as lo-ii mm. long. In 

 the first stage of anthesis the dehisced anthers project ; in the second stage usually 

 only one branch of the style protrudes, the other being vestigial as a rule. Hermann 

 Miiller explains this last peculiarity as an adaptation to the visits of humble-bees. 

 When one of these thrusts its head into a flower, one branch of the style would get 

 in the way of the other were both equally developed. A more complete pollination 

 of the entire stigmatic surface of one branch by the head of the humble-bee is 

 possible when the other branch is absent. Kirchner says that anthesis begins at 

 an intermediate zone of the capitulum, and extends both inwards and outwards 

 from this. 



