IS" SETEHAL SPECIES OE THE OEXUS LI^-USI. 77 



hours, had penetrated the stigmatic tissue, but to what depth I 

 did not ascertain. In this case the inaction of the pollen-grains on 

 their own stigmas must be due either to tlio tubes not reaching 

 the ovules, or reaching them and not efficiently acting on thorn. 

 In the case of Li/thrum Salicaria, which I hope at some future 

 time to lay before the Society, there are three distinct forms, each 

 of whicli produces two kinds of pollen ; but neither 2)ollen, when 

 placed on its own stigma, causes fertility, except occasionally and 

 in a vevj moderate degree ; yet the pollen-tubes in each case freely 

 penetrate the stigmatic tissue. 



The plants of L. perenne and oi L. grandiflorum grew, as stated, 

 with their branches interlocked, and with scores of flowers of the 

 two forms close together ; they wore covered by an open net, 

 through which the wind, when high, passed ; and such minute in- 

 sects as Thrips could not, of course, be excluded ; yet we liave 

 seen that the utmost possible amount of accidental fertilization on 

 seventeen long-styled plants in the one case, and on eleven plants 

 in the other case, was the production, in eacli, of three poor cap- 

 sules ; so that we may infer that, when the proper insects are ex- 

 cluded, the wind does hardly anything in the way of carrying 

 pollen from plant to plant. I allude to this fact because botanists, 

 in speaking of the fertilization of plants or of the production of 

 hybrids, often refer to the wind or to insects as if the alternative 

 were indifferent. This view, according to my experience, is en- 

 tirely erroneous. "When the wind is the agent in carrying pollen, 

 either from one separated sex to the other, or from hermaphrodite 

 to hermaphrodite (which latter case seems to be almost equally 

 important for the ultimate welfare of the species, though occurring 

 perhaps only at long intervals of time), we can recognize structure 

 as manifestly adapted to the action of the wind as to that of 

 insects when they are the carriers. We see adaptation to the 

 wind in the incoherence of the pollen, in the inordinate quantity 

 produced (as in the Coniferse, Spinage, &c.), in the dangling anthers 

 well fitted to shake out the pollen, in the absence or small size of 

 the perianth or in the protrusion of the stigmas at the period of 

 fertilization, in the flowers being produced before they are hidden 

 by the leaves, in the stigmas being downy or plumose (as in the 

 Gramineai, Docks, and other plants) so as to secure the cliance- 

 blown grains. In plants which are fertilized by the wind, the 

 flowers do not secrete nectar, their pollen is too incoherent to be 

 easily collected by insects, they have not bright-coloured corollas 

 to serve as guides, and they are not, as far as I have seen, visited 



