330 ANGIOSPERMAE—DICOTYLEDONES 



readily takes place in the homogamous flowers. In submerged blossoms this is 

 effected pseudo-cleistogamously (Hansgirg), or cleistogamously (Hildebrand, ' D. 

 Geschlechts-Vert. b. d. Pfl.,' p. 77), and always in a closed air-chamber (Kerner). 



749. Polycarpon Loefl. 



2417. p. tetraphyllum L. — The minute flowers of this species (only 2 mm. 

 broad) are always closed like buds, and according to Batalin, have five boat-shaped 

 sepals winged on the back, while the petals are scarcely visible. Fertilization is 

 effected cleistogamously (Batalin). 



750. Corrigiola L. 



2418. C. littoralis L. (Wamstorf, Verb. bot. Ver., Berlin, xxxviii, 1896.) — 

 The small, white flowers of this species are arranged in crowded spikes, and for the most 

 part remain closed (pseudo-cleistogamous). The anthers are dark violet in colour 

 and dehisce laterally. They project beyond the stigma, and autogamy is therefore 

 brought about. The pollen-grains are pale yellow in colour, smooth, spheroido- 

 tetrahedral, only 10-12 /a in diameter. 



751. Paronychia L. 

 3419. P. capitata Lam. Flowers white. 



Visitors. — Macleod (Pyrenees) saw Hymenoptera (i) and Diptera (i). 



752. Telephium Toum. 



2420. T. Imperati L. (Kerner, 'Nat. Hist. PI.,' Eng. Ed. i, II, pp. 173, 213, 

 308.) — At the beginning of anthesis, the stigmas occupy the middle of the flower and 

 are close together, while the anthers are mature, and present their pollen to visitors. 

 Subsequently, when the stigmas have become receptive and diverge, autogamy is 

 prevented, for the concave petals, which previously spread out like a star, come 

 together and cover the anthers, so that only cross-pollination is possible. 



753. Scleranthus L. 



Literature. — Knuth, ' Bl. u. Insekt. a. d. nordfr. Ins.,' p. 73. 



Flowers inconspicuous, apetalous, whitish or greenish ; homogamous, proto- 

 gynous or protandrous ; with half-concealed nectar secreted by the thickened bases of 

 the sepals, and a ring at the base of the ovary. 



2421. S. annuus L. (Knuth, ' Bl. u. Insekt. a. d. nordfr. Ins.,' p. 73 ; Schulz, 

 ' Beitrage,' I, p. 39, II, p. 76.) — The green flowers of this species are homogamous. 

 At first the stamens are pressed against the bell-shaped calyx, so that at this stage 

 cross-pollination may be effected by insect-visits. The stamens subsequently become 

 erect, so that anthers and stigmas are brought into contact, and automatic self-pollina- 

 tion consequently takes place. The amount of nectar secreted in the base of the 

 flower is very limited. These are the facts I observed on the island of Amrum. 

 Schulz at Halle also noticed slight protandry, as well as gynodioecism and gyno- 

 monoecism (5-10 %), rarely andromonoecism and androdioecism. The same writer 



