420 



ANGIOSPERMAEDICOTYLEDONES 



Hermann Muller 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. Herm. Muller noticed 2 hover-flies. 



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



Loew observed that the 

 bees which visit the pro- 

 tandrous flowers 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. Muller, '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. /tides pe/raeum, WulJ. (after Herm. Muller) 

 from above (x 7'. B. The same in longitudinal section. 

 tt, nectary ; ov, ovary ; p, petal ; s, sepal ; st, stigma. 



A. Flower 

 a, anther ; 



FlG. 139. /tides Grossularia, L. (from nature). A. Flower in the first (male) stage : the anthers have 

 dehisced, the stigma is still immature. B. Flower in the second (hermaphrodite) stage; the stigma is now 

 mature. C. Flower after fertilization : the sepals have curved inwards, a, anther ; ca, calyx ; co, corolla; 

 ov, ovary ; s, stigma. 



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

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

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

 Nectar 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, 



