378 



ANGIOSPERMAE—DICOTYLEDONES 



to Warnstorf (Schr. natw. Ver., Wernigerode, xi, 1896), only the uppermost flowers 

 of the capitula are female, as a rule, and are in a minority ; the other flowers are 

 male, often with an isolated hermaphrodite flower here and there between them. 

 The anthers are yellow, and pendulous on long reddish filaments. The hermaphro- 

 dite flowers possess but few stamens. The pollen-grains are of a dirty yellowish- 

 white colour, rounded-polyhedral, smooth, up to 37 /i in diameter. Ludwig says that 

 not infrequently there are variations in the colour of the stamens of different male 

 flowers, from which the anthers hang down limply on long thin filaments. As a rule 

 the anthers are yellow, and the filaments white ; but stocks also occur in which 

 the filaments are red, and the anthers yellowish-red to red. In the female flowers the 

 style and the large spreading stigma are red to wax-yellow or white. 



Visitors. — Herm, Miiller ('Fertilisation,' p. 236) saw a wasp (Odynerus parie- 

 tum L. 5) settle on the flowers, flying away again after a short and profitless search. 

 I noticed a hover-fly (Melanostoma mellina Z.), po-dvg., on the inflorescence. 



In Dumfriesshire a Tenthredinid and 2 hover-flies were recorded (Scott-Elliot, 

 'Flora of Dumfriesshire,' p. 61). 



Fig. 119. Sangitisorba officinalis, L. (after Herm. Mullen. A. Flower seen directly from above. 

 B. The same, seen from the side. C. The same, in longitudinal section. D. Single sepal, seen from 

 within. (X 7) a, anther; br, bract; ca, receptacle; Ji, filament; gr, style; /;, drop of nectar: 



»;, nectary ; oi\ ovary ; s, sepal ; si, stigma. 



909. S. alpina Bunge. — In this species, as in Thalictrum aquilegiifolium, the 

 filaments are claviform, and therefore shaken by the slightest breath of air, so that 

 the pollen is scattered (Kerner, 'Nat. Hist. PI.,' II, p. 145). 



255. Poterium L. 



910. P. spinoslun L. — Pirotta states that this species is anemophilous 

 (Annuario R. Inst. Bot. Roma, iii, 1887). Hermaphrodite flowers are only to be 

 found on cultivated plants : wild ones (in Sardinia) bear only unisexual flowers, and 

 purely female inflorescences are commoner than such as bear both kinds of flowers, 

 while the number of male flowers in the latter is seldom larger than that of the 

 female ones. Cultivated plants more frequently bear polygamous inflorescences 

 than purely female ones. 



911. P. polygama Waldst. et Kit. — Kerner describes this species as trimonoe- 

 cious. The number of stamens in the hermaphrodite flowers is sometimes reduced 

 from 8 to I. 



