THE DISPERSION OF SEEDS AND SPOUES. 101 



XI. 



THE DISPERSION OF SEEDS AND SPORES. 



BY REV. ALEX. S. WII^ON, M.A., B.SC. 



PART II. 

 [Read 21th September, 1880.] 



6. Insects. — Many animals aid in the dispei'sion 

 of plant germs, but insects are bj' far the most im- 

 portant of these. It is almost exclusively as carriers 

 of pollen, however, that they are serviceable to 

 plants. In the vast majority of flowering-plants it 

 is by the instrumentality^ of winged insects that the 

 distribvition and delivery of the pollen is effected. 

 The insects of most importance in relation to the 

 cross-fertilisation of flowers are bees, butterflies, 

 moths, and in a less degree "n^asps, flies, and beetles. 

 The whole floral apparatus— the honey, odour, and 

 brilliant colours, as well as the shape of the flower 

 and the position of its parts — have reference to the 

 visits of insects, and tend to pi'omote cross-fertilisa- 

 tion through their agency. Among the Cryptogams 

 we know as yet of no instance in which fertilisation 

 is effected by animal agency, unless we regard the 

 Floridese as an exception. Insects are so abundant 

 in almost every situation that it is not beyond the 

 limit of possibility that there may exist fungi which 

 depend on special insects for the distribution of 

 their sperm-cells. Insects are at least known to 

 assist in dispersing the germs of certain parasitic 

 organisms. Many diseases are conimiinicated by 

 flies. Indeed, it is not improbable that they may 

 often be to blame for the spread of infection. 



