DISPERSION OF POLLEN BY THE WIND. 129 



pollen, but also the honey from being spoilt by the wet. The narrowing of 

 the corolla-tube and the barricading or complete closing of the entrance to the 

 flower also serve, on the other hand, to keep out certain honey-seeking creatures 

 whose visits would not be advantageous to the plant. Finally, these same con- 

 trivances may ward off also such insects as would remove the pollen without 

 conveying the least particle of it to other flowers. In connection with this last 

 function there exist, no doubt, special adaptations besides, one of the most 

 striking of which occurs in the Monkey Flower (Mimulus) and in the Hemp- 

 Nettle (Galeopsis), and is shown in the illustration of a stamen of Galeopsis 

 angustifolia (fig. 216 19 , p. 91). In this instance the anthers are furnished with 

 two lids which can only be opened by a certain proportion of the insects 

 visiting the flowers. Insects with bodies of such a size that when they enter 

 the flower they rub the pollen from the anthers on to their backs are able to 

 lift the lids of the anthers by brushing against them, and they thus expose 

 the pollen. On the other hand, smaller animals which would not load their 

 backs with pollen on visiting the flowers in question or would not convey it to 

 the stigmas of other flowers are not strong enough to open the anthers. Thus 

 the pollen is effectively protected by means of these lids against the detrimental 

 action of small-sized plunderers. 



DISPERSION OF POLLEN BY THE WIND. * 



At the beginning of the last chapter it was stated that the medium wherein 

 the transport of the pollen to the stigmas takes place is, in the great majority 

 of Phanerogams, the air. For the conveyance of pollen between flowers situated 

 at a distance from one another there exist two main agents, viz. the wind and 

 insects. Hence Phanerogams have been distinguished by botanists into "anemo- 

 philous" or wind-fertilized, and " entomophilous " or insect-fertilized plants. But 

 these terms, which are adopted in most works on Botany, can only be used in 

 a strictly limited sense. It is no doubt true that there are plants in which the 

 transference of the pollen to the stigmas is effected exclusively by the wind, and 

 others in which the equivalent process takes place solely through the intervention 

 of animals; but, on the other hand, it has been ascertained in the case of a large 

 number of plants that whereas shortly after the flowers open small creatures 

 carry off the pollen and convey it to other flowers, later on, when the flowering 

 period is drawing to a close, the pollen is committed to the wind and by it 

 transferred to the stigmas of neighbouring blossoms. The best instances of this 

 are afforded by several of the Rhinanthacese, as, for example, Bartsia and the 

 Toothwort (Lathrcea), and by many Ericaceae, such as Calluna vulgaris and 

 Erica carnea, but many more could be mentioned. The conformation of the 

 various parts of these flowers when they first open renders a dispersal of the 

 pollen by the wind impossible; but in fine weather insects visit them in large 

 numbers, and in the act of sucking the honey load themselves with pollen 

 VOL. II. 59 



