420 



ANGIOSPERMAE—DICOTYLEDONES 



Hermann IMuller as homogamous. As in the other species, cross-fertilization is 

 favoured when insects visit the flowers, but automatic self-pollination readily takes 

 place should they fail to do so. 



Visitors. — Harm. Miiller noticed 2 hover-flies. 



990. R. niveum DC. (Loew, ' Blutenbiol. Beitriige,' I, pp. 11-14.) — 



Loew observed that the 

 bees which visit the pro- 

 tandrous (lowers of this 

 species insert their- pro- 

 boscis just above the petals 

 into the slit between the 

 bases of the filaments, 

 thus pressing the anthers 

 against the under-side of 

 their body. When visiting 

 a flower in the second 

 (female) stage, pollen is 

 necessarily deposited on 

 the receptive stigmas. 

 Visitors. — Loew observed a bee (Anthophora pilipes F.) and a humble-bee 

 (Bombus agrorum F.) in the Berlin Botanic Garden. 



991. R. Grossularia L. (Herm. Mailer, 'Fertilisation,' 250-1, 'Weit. Beob.,' 

 I, p. 300 ; Kirchner, ' Flora v. Stuttgart,' p. 409 ; Knuth, ' Bloemenbiol. Bijdragen.') — 

 The flowers of this species belong to class C. The anthers dehisce as they open, 



Fig. 138. Ri/>es pclraeum, WulJ. (after Herm. Muller), A. Flower 

 from above ( >. 7'. B. The same in longituiiiiial section. a, anther; 

 «, nectary ; ov, ovary ; /•, petal ; j, sepal ; j/, stigma. 



Fig. 139. Ribes Grossularia, L. (from iiaturet. A. Mower in the first{male) slage : the anthers ha\e 

 <iehisced, the stigma is still immature. H. Flower in the second (hermaphrodite) stage ; the stigma is now 

 mature. C Flower after fertilization : the sep.ik have curved inwards, a, antliri ; (:(?, eal\\; co, corolla; 

 ux\ ovary: s, stigma. 



but the styles are not yet of full leiigih, nor are the stigmas receptive (Hermann 

 Muller). The reflexed sepals of these protandrous flowers are green, usually with 

 reddish tips, while the petals, which arc directed vertically downwards, are white. 

 N'ectar is secreted in the base of the bell-shaped extension of the receptacle, and 

 the access to the secretion is narrowed by contraction of the receptacular margin. 



