322 ANGIOSPERMAE—DICOTYLEDONES 



brought about if cross-pollination fails. Pollen from flowers on other plants is not 

 necessary, as those in the first stage may be crossed with that of others with mature 

 stamens situated lower on the spike. I observed regularly also that in P. maritiraa 

 the stigma not only persisted through the whole hermaphrodite stage, but even 

 elongated several millimetres and remained receptive some time after the stamens 

 faded. Geitonogamy may therefore occur in the last stage, the pollen of flowers at 

 the top of the inflorescence falling on the stigmas of those situated lower. 



Kemer says that the anthers dehisce upwards by means of a short slit only, so 

 that some days elapse before the pollen is shaken out. The dehisced anther-lobes 

 close during dewy nights and damp weather, thus preventing the pollen from being 

 spoilt by wet. Pollen-collecting bees damp the dry pollen-grains with regurgitated 

 nectar. 



2392. P. major L. (Schulz, 'Beitrage,' II, pp. 152-3, 197; Kirchner, 

 ' Flora V. Stuttgart,' p. 647.) — Schulz states that this species varies between homogamy 

 and protogyny ; the length of the style is also frequently variable. Most stocks 

 possess brownish corollas, white filaments, and red-brown anthers ; Ludwig, however, 

 says that forms occur with yellow or greenish-yellow anthers, which are larger and 

 broader and more rounded at the top. Stocks with white anthers are found rarely. 

 Schulz observed gynomonoecism and gynodioecism, but the number of female flowers 

 is small, and seldom exceeds 10 %. 



2393. P. lanceolata L. (Delpino, ' Applicaz. d. teor. Darwin.,' p. 6 ; Herm. 

 Muller, 'Fertilisation,' pp. 503-6; MacLeod, Bot. Jaarb. Dodonaea, Ghent, v, 1893, 

 p. 362; Schulz, 'Beitrage,' I, pp. 90-2, II, pp. 174-98; Kirchner, 'Flora v. Stutt- 

 gart,' pp. 646-7 ; Knuth, ' Bliitenbesucher,' p. 9, ' Blutenbiol. Beob. in Thiiringen,' 

 ' Bloemenbiol. Bijdragen.') — This species is gynodioecious and gynomonoecious with 

 protogynous hermaphrodite flowers. The receptive stigma projects about a mm. 

 from the hermaphrodite flowers before the corolla opens, while the anthers, of which 

 the filaments are still short, are enclosed in the bud. When the stigma begins to 

 shrivel, the filaments elongate and project 5-6 mm. from the flower when the trans- 

 parent corolla opens, the anthers dehiscing and scattering their pollen at the same 

 time. 



Schulz states, however, that the hermaphrodite flowers are not always so strongly 

 protogynous, but in many cases the stigma only matures when anthesis begins. The 

 length of the style varies. 



Ludwig distinguished (in 1879) two forms : in one the anthers were white and 

 heart-shaped, in the other they were oblong; their colour varied between greenish 

 and sulphur-yellow, and their pollen-grains were generally reduced. 



Hermann Muller describes two forms, united by transition stages. 



(i) Low-growing plants, found in sunny, hilly stations; these bear rounded 

 spikes 5 mm. in diameter, with stalks which are often scarcely 10 cm. long. The 

 anthers project 5-6 mm. from the flower. 



(2) Tall plants, growing on alluvial meadows, bearing spikes 15-30 mm. long 

 with stalks 30-44 cm. in length. The anthers project 6-7 mm. from the flower. 



Delpino distinguishes three forms. 



(i) Long-scaped plants growing in meadows, with very broad whitish anthers 



