142 NATURAL FERTILISATION 



fertilised by very minute insects is afforded by the Sweet 

 Violet and the Pansy. 



If attention is paid to the arrangement and position of 

 the stigmas and stamens at the time when insects are seeking 

 the flowers for the sake of the honey, it will be seen that the 

 anthers are almost always at this time discharging their pollen, 

 and that it is impossible for the insect to find its way to the 

 nectary, or to insert its proboscis into it, without brushing 

 against one or more of the anthers, and carrying away with it 

 a portion of the pollen. Either in its retreat from the flower 

 or in entering the next flower (of the same species) which it 

 visits, it will also almost inevitably strike against the stigma 

 and leave some of the pollen-grains behind on it, which will 

 then put out their tubes and fertilise the ovules. But, inas- 

 much as in by far the majority of cases the stigma is not " re- 

 ceptive," or in that papillose and viscid condition in which 

 alone it incites the emission of the pollen-tubes, at the same time 

 that the pollen is being discharged from the anthers in the 

 same individual flower, provision is thus made for that " cross- 

 fertilisation " which we have already spoken of as the general 

 rule ; and, indeed, in many cases no other mode of fertilisation 

 is possible. 



Flower-arrangements for Cross-fertilisation. 



Readers of botanical literature are now so familiar with 

 illustrations of the infinite variety and beauty of the contriv- 

 ances for the cross-fertilisation of flowers by insect agency, that 

 we do not propose to give any more here. The simple ar- 

 rangement by which the pistil and stamens in the same flower 

 arrive at maturity at different times may be noticed without 

 difficulty by the most careless observer. It is only necessary 

 to gather the common Rib-grass (Plantago lanceolatd) to observe 

 that the feathery stigmas are produced from the still half-closed 

 bud or before the stamens are nearly mature ; and the same is 

 the case with the waterside Figworts (Scrophularia nodosa and 

 aquatica). The reverse, however, is far more common, and 

 may be well seen in almost any plant belonging to the natural 

 order Caryophyllaceae, as, for example, any of the common 

 species of Stitch wort (Stellar ia Holostea or graminea), where 

 the anthers have actually dropped off the filament before the 

 stigmas have acquired their receptive condition. The Hare- 

 bell, or any other species of Campanula, wild or cultivated, 

 will illustrate the same phenomenon. A singular circumstance 



