RANUNCULACEAE 39 



80. H. niger L. (Knuth, Bot. Centralbl., Cassel, Ivii, 1894.)— In spite of the 

 very large white flowers insect visitors are extremely few, no doubt because the un- 

 favourable flowering season usually deters them from flying about. The flowers 

 in all respects agree in structure with those of H. viridis. Warnstorf (Schr. natw. 

 Ver., Wernigerode, xi, 1896) says that the number of the nectaries is about 10-12. 

 The white, smooth, ellipsoidal pollen-grains average 53 jj. in length, and 28 /x in 

 breadth. 



Visitors. — I observed at Kiel only Apis mellifica Z. 



81. H. siculus Schff. — native to Etna — agrees essentially in its anthesis (Nicotra, 

 Boll. Soc. bot. ital., Firenze, 1894) with the other species of Helleborus described 

 by me, more particularly with H. viridis. This Sicilian species is also protogynous. 

 The nectaries only begin to secrete when the anthers dehisce. Autogamy is com- 

 pletely prevented, for the stigmas have withered by the time the first anthers have 

 shed their pollen. 



82. H. atrorubens Waldst. et Kit. — 



Visitors. — Loew observed — in the Berlin Botanic Garden — the honey-bee, 

 po-cltg„ and saw it also on 



83. H. cyclophyllus Boiss., and 



84. H. lividescens A. Br. et Sauer, as well as on 



85. H. pallidus Host, on which species in the same place he also noticed 

 one of the Muscidae (Scatophaga stercoraria Z.). 



i6. Isopyrum L. 



Flowers with half-concealed nectar. The sepals serve as the chief means 

 of attracting insects. The petals are modified into shovel-shaped nectaries, and are 

 considerably smaller than the sepals. 



86. I. thalictroides L. (Kemer, 'Nat. Hist. PI.,' Eng. Ed. i, II, p. 120.)— 

 Soon after the white flower has opened the anthers of the outermost staminal whorl 

 dehisce, and at the same time the filaments bend over so as to bring them above 

 the nectaries, in which position they must necessarily be brushed against by nectar- 

 sucking insects. Next day these stamens move outwards towards the reflexed 

 sepals, while simultaneously the next whorl of stamens dehisce, and bend over the 

 nectaries. On the third day these in turn move outwards, their place being taken 

 by the members of the third whorl, and so on in succession till all the stamens have 

 brought their anthers above the nectaries. Insects alighting upon the middle of 

 the flower must of necessity effect cross-pollination if they have already visited 

 another blossom of the same species. 



Visitors. — Nothing is known about these. 



17. Nigella Toum. 



Markedly protandrous bee-flowers. The large brightly coloured sepals serve 

 to attract insects. The eight petals are converted into nectaries of a characteristic 

 kind. They possess a hollow claw, bent like a knee, and a split limb provided with 



