58 Flowers and their Unbidden Guests. 



that their base must be crossed by any insects that 

 creep up from below, as, for example is the case in 

 Saponaria porrigens, Sap. glutinosa, Angelonia grandi- 

 flora, Silene noctiflora, Senedo viscosus, etc., then the 

 glandular hairs contribute most certainly to the 

 exclusion of these insects ; and, as a very instructive 

 instance, showing that it is of advantage, even to plants 

 with very small flowers, to be insured against the 

 visits of creeping insects by trichomes on their sessile 

 leaves, I wiU here describe more particularly the last in 

 the above list, namely, Senecio viscosus. In this plant 

 the distance between the mouth of the small corolla- 

 tube, which is full of nectar, and the point of the pro- 

 jecting style (which at the first stage of the flowering 

 carries the pollen, and at a later period exposes the 

 stigmatic surfaces), is not more than half a millimetre ; 

 and flying insects, that make their approach either from 

 above or from the side, must unavoidably come in con- 

 tact with the stigma and with the poUen in due succes- 

 sion, even though their organs of suction and the 

 anterior part of their bodies be scarcely half a milli- 

 metre across. 



Creeping insects, on the contrary, though of precisely 

 similar dimensions in these parts, could, inasmuch as 

 they make their approach from below, get at the nectar 

 without touching the stigma at all, as this stands out 

 above the corolla-tube, and so without bringing about 

 allogamy. Their visits, therefore, are always unprofit- 



