COMPOSITAE 



60 1 



Fig. 197. Btdeiis tripartita, L. (from 

 nature). (1) Tip of style, with sweeping-hairs. 

 in opening floret. (2) Ditto, of floret in female 

 stage : stylar braoches recurved, and beset with 

 stigmatic papillae internally. ( 20.) 



437. Bidens L. 



Ray-florets sometimes absent in German species ; ligulate, neuter, coloured like 

 the hermaphrodite tubular disk-florets. Stylar branches with lancet-shaped tips, 

 covered externally by strong sweeping-hairs, and beset with numerous stigmatic 

 papillae internally. 



1410. B. tripartita L. (Hildebrand, ' tJ. d. Geschlechtsverhalt. b. d. Compositen,' 

 p. 67, Taf. I, Figs. 30-1; MacLeod, Bot.Jaarb.Dodonaea, Ghent, V, 1893, pp. 416-17; 

 Knuth, 'Bl. u. Insekt. a. d. nordfr. Ins.,' pp. 88, 157.) — Ray-florets are almost always 

 wanting in this species. The diameter of the head is at most i cm. The sweeping- 

 hairs at the tip of the style are moderately long, the next below are shorter, and the 

 lowest are the longest. They brush out the 

 pollen from the anther-cylinder, which after- 

 wards becomes completely retracted into the 

 corolla-tube. The stylar branches then unfold 

 their papillose inner sides ; the corolla-lobes 

 so far spread out at the same time resume 

 a nearly vertical position ; and the pappus 

 bristles, with deflexed prickles on their outer 

 sides, spread out so that the diameter of the 

 head is xiltimately increased to 2^ cm. The 

 florets are at first yellow, but towards the end of 

 anthesis assume an inconspicuous brown colour. 



Visitors. — MacLeod (Belgium) saw. 2 bees (Bombus and Andrena). 

 I noticed at Kiel 3 hover-flies (i. Melithreptus taeniatus iW^. ; 2. Platycheirus 

 manicatus Mg. ; 3. Syrphus balteatus Deg.), and a bug (Calocoris bipunctatus F^. 



1411. B. cemua L. (Herm. Miiller, ' Weit. Beob.,' Ill, p. 88; MacLeod, 

 op. cit. ; Knuth, ' Bloemenbiol. Bijdragen,' ' Bliitenbiol. Herbstbeob.') — In this 

 species about 100 yellow florets are aggregated into a head. Hermann Miiller 

 states that each disk-floret has a corolla-tube about i^ mm. long, with a bell 

 of about the same length and i mm. in width. In the first stage of anthesis 

 the pollen-covered anther-cylinder projects about i mm. from the bell, and in the 

 second stage the stylar branches (also i mm. long) diverge. The mechanism of 

 these branches agrees with that described for B. tripartita. The stigmatic papillae 

 are so broad that pollen-grains of the same flower may readily remain adhering 

 on the margin, so that automatic self-pollination is possible, as it is also in the last 

 species. There are three varieties. — 



(a) discoidea Wimm. ; ray-florets absent ; 



(5) radiata DC. (=Coreopsis Bidens Z.); large ray-florets; 



(c) minima L. ( = B. minima Z.); plant low (stem only 4-10 cm. high); 

 usually only one small head. 



Visitors. — Herm. Miiller saw only the honey-bee at Lippstadt. 

 At Kiel I observed a humble-bee (Bombus terrester Z. 5, skg.) and a Muscid 

 (Lucilia cornicina F., po-dvg.). 



