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A TEXTBOOK OF THEORETICAL BOTANY 



In S. granulata the white flowers (Fig. 1547) are markedly protandrous, 

 with nectaries situated on the upper side of the ovary. The calyx holds the 

 petals so closely together that they form a tube in the base of which the 

 nectar is protected from the rain. When the flowers first open the anthers 

 are unripe and the filaments short. Then two of them elongate and 



Fig. IS47- — Saxifraga aramilala. Longitudinal sections of flower at successive stages 

 of development, showing protandry. {After Kniith.) 



assume oblique positions so that their anthers, which have dehisced mean- 

 while, lie immediately over the style. When these anthers have shed their 

 pollen they bend back towards the petals and two or three others take their 

 place. Pollen is shed over a period of about three days during which time 

 the styles with their immature stigmas lie close together. Only after all the 

 pollen has been shed do the styles elongate and the stigmas diverge so as to 

 occupy the position previously taken up by the anthers (Fig. 1548). Beetles 



Fig. 1548. — Saxifraga biirseriana. Flower in 

 female stage with stigmas exserted. 



