238 TRANSACTIONS AND PROCEEDINGS OF [Sess. lvi. 



of the earlier orders of British plants. The names of the 

 insects observed will be found in my " Flora of Dumfries- 

 shire," part i., but there are certain conclusions derived 

 from my observations which may, perhaps, be worth giving 

 here. 



There has been during recent years a tendency to 

 minimise the importance of insects as agents in effecting 

 fertilisation. Meehan* and also Schulz,t for instance, 

 have tried to show that self-fertilisation is, in all cases, 

 the regular method, and that insect-fertilisation is only of 

 occasional assistance. Henslow| has, to a certain extent, 

 supported similar views, though not, I think, accepting them 

 in the extreme just stated. 



Of course, the only way of proving or disproving dogmatic 

 assertions of this kind is by an appeal to observation. Can 

 any series of plants be found in which insect-visits are so 

 rare that the above statement is strictly within the facts ? 

 If such a series can be discovered, it must surely be amongst 

 the plants of the early " weedy " orders of Thalamitlorie. 

 The plants studied by me this summer were almost all of this 

 nature, and were, in fact, as many of the Biitish species up 

 to the end of Cruciferaj as were common in the district 

 about Dumfries. 



The flowers of the majority of these plants are small and 

 inconspicuous ; most are white or yellow in colour ; and they 

 are therefore all, as " weeds," more likely to be dependent on 

 self-fertilisation. The modifications in their structure for 

 insect-visits are, in almost every case, very slight and un- 

 important. They are, moreover, in chiefly Dipterous flowers, 

 and it is amongst these that one is most likely to find self- 

 fertilisation. Flies are particularly sensitive to bad weather, 

 and are sometimes prevented by wind or rain for several 

 days from visiting flowers. Flence the advantage of possible 

 self- fertilisation seems obvious enough. In fact, there could 

 not be primd facie a set of plants more likely to uphold the 

 theory of Meehan and Schulz that insect-visits are only of 

 occasional assistance, than those in the following Table. 

 Yet what is the result ? I found insect-visits universal. 



* Mcelian, in Arnci-icjm Naluralist,, vnls. xii., xiii., &c. 

 + Sclml/C, in J>il)liotlic(;a Dotanica, Hcit x. and xvii. 

 + Ilcnslow, in Trans. Linn. Soc, 1869. 



