24 ANGIOSPERMAE—DICOTYLEDONES 



ment, and exhibit complete mutual adaptation as regards both size and general 

 structure. 



Lindman states that on the Dovref jeld the flowers of R. acris sometimes possess 

 an agreeable, slightly sweet odour : the diameter of the flowers is 15-25 mm. : the 

 visitors are numerous flies, and also Lepidoptera. According to Ekstam, flowers of 

 the variety borealis Trautv. — in Nova Zemlia — have a diameter of 30 mm., and are 

 slightly protogynous, protogynous-homogamous, protandrous-homogamous, or homo- 

 gamous. Flies were observed as visitors. In central Germany, Schulz also observed 

 gynomonoecism. 



R. repens — according to Lindman — is also homogamous on the Trontfjeld. 

 Schulz states that this species also is gynodioecious in central Germany. 



The same is true — according to Whitelegge — for R. bulbosus in England. 



The species R. repens, R. acris, and R. Flammula^ exhibit in the East Frisian 

 islands (Verhoeff, ' Bl. u. Insekt. a. d. Ins. Norderney,' pp. 108-14) three very 

 important and interesting degrees of adaptation to insects. The actual kind and 

 frequency of insect-visits harmonize most beautifully with these adaptational stages. 

 Verhoeff^ says that R. repens has an advantage over R. acris in the following 

 characters: — (i) the nectary and nectar-scale are better developed; (2) the stamens 

 diverge outwards more readily, usually projecting beyond the calyx — which seldom 

 happens in R. acris ; (3) the petals are broader and more lustrous ; and (4) the 

 flowers are more crowded. 



Verhoeff makes the following comparison between R. acris and R. repens on 

 the one hand, and R. Flammula on the other, with regard to the times at which 

 the sexes develop. — 



R. acris and R. repens. R. Flammula. 



The stigmas are mature before any of The stigmas are undeveloped when 



the anthers have dehisced, and are at the the first marginal anthers dehisce, but 



same time exposed to contact with the mature while the rest of the outer anthers 



under-sides of insects. are ripening. 



In flowers where all or some of the 

 innermost anthers have dehisced, the 

 carpels are already swollen and their 

 stigmas shrivelled. 



The stigmas may either be a little The stigmas project above the adjacent 

 higher or a little lower than the adjacent anthers from the first, 

 anthers. 



Protogyny. Approach to protogyny. 



In Westphalia, Hermann Miiller has not noticed any differences between 

 R. acris, R. repens, and R. bulbosus. On the contrary, he expressly remarks 



' Verhoeff says : ' H. Miiller has made a mistake with regard to the species of Rannnculns, 

 wrongly asserting that K. acris, repens, and Flammula agree as regards structure and conspicnous- 

 ness.' This, however, is not quite correct, for Hermann Miiller expressly states that R. Flammula 

 is much more rarely visited by insects than R. acris, R. repens, and R. bulbosus — ' One reason 

 at least being that its flowers are much smaller, and less conspicuous.' ('Fertilisation,' p. 76.) 



