COMPOSITAE 689 



a diameter of 17 mm. All the florets of a head develop simultaneously. The 

 anther-cylinder projects 3-4 mm. from the corolla-tube, and the style 3 mm. beyond 

 this. The stylar branches only roll back far enough to form a semicircle, so that 

 automatic self-pollination is excluded. On the other hand, according to Kerner, the 

 stylar branches of the outer florets diverge far enough to touch the pollen of the 

 inner ones, thus automatically effecting geitonogamy. Warnstorf states (Verh. bot. 

 Ver., Berlin, xxxviii, 1896) that the florets open at Neu-Ruppin about 10 a.m., closing 

 again between 2 and 3 p.m. The pollen-grains are golden-yellow in colour, spherical, 

 densely covered with spinose tubercles, irregular in size, up to 50 /x in diameter. 



Visitors. Schletterer records the bee Dasypoda plumipes Pz. for the Tyrol, 

 and observed the fossorial wasp Notogonia pompiliformis Kohl at Pola. 



499. Prenanthes Vaill. 



Florets purple-red. Style entirely covered with pointed sweeping-hairs directed 

 obliquely upwards, and extending considerably below the cleft : stylar branches 

 beset internally with stigmatic papillae, and rolling far back. Kerner says that 

 geitonogamy is brought about by the intertwining of the stylar branches of neigh- 

 bouring florets when these begin to fade, so that the stigmas become dusted 

 with any pollen that may remain. 



1635. P. purpurea L. In this species, according to Hermann Muller (' Weit. 

 Beob.,' Ill, pp. 95-6), the heads consist of only 4-6 florets. The involucre is 

 12-14 mm ' l n g> Dut on ty 2 mm - broad; the purple-red florets projecting from 

 it possess ligules 10 mm. long and 3-4 mm. broad, so that the heads are moderately 

 conspicuous. At a later stage the style projects 7 mm. beyond the anther-cylinder, 

 which is 56 mm. long and scarcely f mm. broad. Finally, the stylar branches 

 (3 mm. in length) diverge and roll back into a spiral of i or 2 turns, so that in the 

 absence of insect visitors automatic self-pollination is effected. 



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

 stated. 



Herm. Muller (Bavarian Oberpfalz), a beetle (Agrilus coeruleus Rossi), a Muscid 

 (Sarcophaga carnaria Z., po-dvg.), and 2 bees (Apis, freq., skg. and po-cltg.), and 

 Andrena denticulata K. 5). Hoffer (Steiermark), the humble-bee Bombus hypnorum 

 Z. J. Schletterer and von Dalla Torre (Tyrol), 2 humble-bees (Bombus confusus 

 Schenck, and B. mastrucatus Gerst. <j>). MacLeod (Pyrenees), a Muscid (Bot. Jaarb. 

 Dodonaea, Ghent, iii, 1891, p. 368). Loew (Berlin Botanic Garden), Apis, skg. 



500. Lactuca L. 



Florets yellow, rarely lilac in colour. Structure of the style as in Prenanthes. 

 Kerner says that geitonogamy takes place when the florets begin to fade. He also 

 states that the milky juice of many of the species is a protection against destructive 

 animals. 



1636. L. Scariola L. (Kirchner, 'Beitrage,' p. 72.) Kirchner says that the 

 diameter of the yellow heads, which consist of 20 florets, is about 20. mm. when 

 fully open. Even before complete expansion, the pollen-covered style grows out 



davis 11 y y 



