THE VICTORIAN NATURALIST. 99 



Striking characteristic of these exclusively wind-fertilized plants is 

 the absence of fragrant and bright-coloured flowers, while the in- 

 terior of the flower is destitute of honey and perfume ; among 

 such may be mentioned conifers, beeches, poplars, walnut, many 

 palms, and the grasses and sedges. It is of no advantage to these 

 flowers to be visited by insects, and accordingly they have no 

 need of any devices for attracting bees, butterflies, or flies. Of 

 course the flowers of the plants in question are not infrequently 

 visited by insects, but these visitors play only a very subordinate 

 part in the dispersion of the pollen. 



Wind-storms, whether with or without rain, are anything but 

 beneficial in the dispersion of pollen. The pollen, removed from 

 the spot where it has been crowded together within the province 

 of the flower, and contained in a space about the size of a pin's 

 head, has to be scattered over an area many million times as great. 

 A gradual dispersion is occasioned only by a gentle wind, and 

 thus the light breezes which sweep through valleys shortly after 

 sunrise, ascending air currents, or the alternating land and sea 

 breezes of the coast winds are the most favourable agents of 

 pollination. 



The form of distribution of the stigmas to be covered with dust 

 pollens are also in harmony with these conditions. Most anem- 

 ophilus plants have dioecious or monoecious flowers, and those which 

 develop hermaphrodite flowers exhibit complete dichogamy — that 

 is to say, the androecium and gynoecium ripen at different times, 

 so that when mature pollen is distributed the stigmas of the same 

 flowers are already withered, and therefore not in a condition to 

 receive the pollen cells, or they are still so immature that they 

 cannot be covered with pollen. The pollen has therefore to be 

 blown to other flowers in the neighbourhood, whose stigmas 

 happen to be in the acceptive stage of development. In all these 

 dichogamous plants the flowers with stigmas in the receptive con- 

 dition are situated higher than the anthers from which the mature 

 pollen is committed to the wind. Therefore in order to reach 

 the receptive stigmas the pollen must travel upwards, and it is 

 unquestionably true, in the majority of cases, that the clouds of 

 pollen which are carried off by moderate winds, at first soar up- 

 wards and either directly reach the stigmas awaiting them at a 

 higher level, or later, as the pollen cells sink down, being 

 deposited on the stigmas. 



In some species, at the very moment when the anthers burst 

 open the pollen, is ejected violently into the air and ascends 

 obliquely in form of a little cloud of dust. This phenomenon is 

 afforded by the nettles, whose filaments bearing the anthers are 

 coiled in the bud, and suddenly spring up at the same moment 

 that the dehiscence of the anthers takes place. In all these 

 plants ejection of pollen only ensues when a light dry wind blows, 

 which causes an alteration in the tension of the tissues concerned. 



