PROTECTION OF POLLEN. 



109 



for protection, detach themselves and drop to the ground. Fig. 220^ shows the 

 male flowers of the dioecious Sea-Buckthorn (Hippophae rhainnoides), which are 

 arranged in spikes and are seated in the axils of scaly bracts at the bases of the 

 young lateral shoots. In each flower are four anthers which discharge their 

 abundant powdery pollen whilst the flower is still closed like a bud and has the 

 appearance of a little bladder (fig. 220 ^). This pollen is of an orange colour, and 

 drops to the bottom of the flower, where it remains (figs. 220 * and 220 ^) awaiting 

 a dry wind to transport it to the stigmas of the female flowers growing on 

 other plants often at a considerable distance. Several days may go by before 



1 Impatiens NoHtangere. 2-6 Bippophae rhamnoides. 

 ^. ^> '. ^ ^ natural size ; *, *, ^ slightly magnified. 



Fig. 220.— Protection of Pollen from Wet. 

 « ConvaUctria Tnajalis. 



y Euphrasia officinalis. 8 jris sibirica. 



this kind of wind sets in, and meanwhile there is the danger of the store of 

 pollen being soaked by rain or dew and rendered unfit for dispersion. To obviate 

 this risk the pair of curved perianth leaves, which have their concave surfaces 

 turned towards one another, and form, as has been already mentioned, a kind 

 of bladder inclosing the anthers and pollen, dehisce at the sides only. Thus two 

 opposite gaps (figs. 220 * and 220 ^) are produced, whilst at the top the two valves 

 remain joined together and form an arch completely sheltering the mass of fallen 

 pollen from atmospheric' deposits. When the needful wind arises it blows the 

 pollen out through the chinks in the bladder and conveys it to the stigmas of 

 other plants of the same species. 



Plants of the Globe-flower (Trollius) genus, whose species grow in the Arctic 

 regions in damp situations and also further south in mountainous districts of the 



