CJSTINEAE 133 



are sensitive, and this favours cross-pollination. Automatic self-pollination is effected 

 by closure of the flowers at night and during dull weather. 



Visitors. — These are similar to those of H. vulgare in the Alps (Herm. MuUer), 

 but owing to the smaller size of the flowers are less numerous and belong to fewer 

 species. 



328. H. Fumana Mill. (Schulz, ' Beitrage,' II, pp. 17-18.) — Schulz states that 

 the yellow flowers are homogamous and of variable size. They open only in the 

 forenoon during sunshiny weather. At first self-pollination is prevented by the position 

 of the stigma, but as the stamens move inwards either spontaneously or by insect 

 agency, so as to touch it, automatic self-pollination can be effected. 



Visitors. — Schulz observed bees, flies, and more rarely beetles, in the South 

 Tyrol. 



329. H. oelandicum Wahlenb. ( = H. vineale P^rj.). — Schulz ('Beitrage,' II, 

 p. 18) describes the flowers as homogamous. They are smaller than those of the 

 last species, but not so ephemeral. As the style is less bent than in H. Fumana, 

 there is either contact between anthers and stigma at the beginning of anthesis 

 or the stigma is placed so that pollen falls upon it. 



Visitors. — Schulz observed flies, bees, and beetles. 



MacLeod saw a Syrphid visiting the yellow pollen flowers in the Pyrenees. 



330. H. guttatum Mill. (Verhoeff, ' Bl. u. Insekt. a. d. Ins. Nordemey.') — 

 The citron-yellow flowers open only for a forenoon. There are usually dark-brown 

 pollen-guides on the bases of the petals. The anthers being at a higher level than 

 the large whitish stigma, automatic self-pollination by the fall of pollen can easily 

 take place. It is inevitable after the petals have been shed, for the sepals then close 

 together so as to press the anthers against the stigmas, to which they remain 

 clinging as the fruit matures. Linnaeus (' Amoenitates,' III, p. 396) observed 

 cleistogamy in plants brought from Spain and cultivated in Upsala. 



331. H. salicifolium Pers. — Linnaeus (op. cit.) observed at Upsala that ripe 

 fruits were produced when the flowers remained closed. 



Visitors. — Schletterer noticed the small bee Halictus morio F. at Pola. 



332. H. polifolium DC. — Briquet (' fitudes d. biol. flor. d. les Alpes Occident.') 

 states that the flowers open and close repeatedly, owing to movements of the sepals. 

 The bases of the white petals are of a citron-yellow colour. The numerous yellow 

 stamens are crowded into a bundle in the middle of the flower; their anthers are 

 introrse, but while shedding their pollen turn their dehisced sides more or less 

 outwards. There is no nectar. The style is curved like the letter S, and the stigma 

 is large. The irritability of the filaments — which has long been known — persists 

 throughout anthesis, and affects all the stamens equally. It is most marked in dry 

 weather at a temperature of 18-25° C. Within 1-5 seconds after a filament is 

 touched it has passed from an almost erect position into a nearly horizontal one, 

 owing to the bending of a zone about ^ mm. long immediately above its insertion. 

 After about 15 seconds it gradually resumes its original position, and can then be 

 stimulated afresh. The motile mechanism resembles that of the pulvini of Mimosa 

 leaves. Its oecological significance is found in the fact that when insects (humble- 



