RUBIACEAE 549 



subsequently pushed out by the elongating style. The stigma then matures. 

 Kerner describes the flower mechanism as follows. The long thin serpentiform 

 style bears a thick stigma, which is held fast by the anthers, and gets covered 

 with pollen. By elongation of the style, the stigma is raised to the dome-like 

 top of the still closed flower. When insects alight the petals suddenly open, and 

 the stigma springs out, dusting the visitors with pollen from below. The style 

 with its maturing stigma now projects well out of the flower so that the latter 

 is first touched by the hymenopterous or dipterous visitors. In this way crossing 

 is necessarily effected. Failing insect-visits, the flower explodes, and its scattered 

 pollen is wafted to the stigmas of neighbouring blossoms. 

 Visitors. — Vide supra. 



1265. C. angustifolia L. — The small flowers of this species are greenish- 

 yellow in colour. 



Visitors. — Plateau observed the beetle Cassida nobilis Z., and a bee 

 (Andrena sp.). 



400. Coffea L. 



1266. C. arabica L. — According to Bernoulli (Bot. Ztg., Leipzig, xxviii, 1869, 

 p. 17), only small purely female fertile flowers are present at the beginning of 

 anthesis. Ernst states that the hermaphrodite flowers are protandrous. 



Visitors. — Bourdillon chiefly observed Lepidoptera (Nature, London, xxxvi, 

 1887). 



401. Nertera Banks et Soland. 



1267. N. depressa Banks et Soland. — Francke describes this species as 

 protogynous, autogamy being excluded (Inaug.-Diss., Halle, 1883). 



402. Rondeletia L. 



1268. R. strigosa Hemsl. — According to Penzig (Malpighia, Geneva, viii, 

 1894, pp. 466-75), there are crowded yellow granules on the cup-shaped part of 

 the corolla of this species, which closely mimic pollen-grains, and serve to attract 

 insects. 



LIIL ORDER VALERIANAE DC. 



Literature. — Knuth, ' Grundriss d. Bliitenbiol.,' p. 63. 



The flowers are aggregated into dense cymes, so that though usually small 

 they are rendered conspicuous. The nectar is almost always secreted and concealed 

 in a pouch or spur of the corolla-tube, so that most of the species belong to the 

 flower class S, but those of the genus Centranthus are obviously members of L. 

 Cioss-pollination is secured by dichogamy, more rarely by dioecism (Valeriana 

 dioica). Homogamy is exemplified among the smaller flowers. 



403. Valeriana L. 



FloW'Crs whitish in colour, and arranged in corymbose capitate or paniculate 

 tymes ; protandrous or protogynous ; with concealed nectar, secreted and concealed 

 above the origin of the corolla-tube in a small pouch with a green fleshy base. 



