DISPERSION OF POLLEN BY THE WIND. 129 



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

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

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

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

 ivances may ward off also such insects as would remove the pollen vrithout 

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

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

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

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

 ngustifolia (fig. 216 i», p. 91). In this instance the anthers are furnished with 

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

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

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

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

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

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

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

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

 3tion of small-sized plunderers. 



DISPERSION OF POLLEN BY THE WIND. 



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

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

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

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

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

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

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

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

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

 ;hers in which the equivalent process takes place solely through the intervention 

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

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

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

 3riod is drawing to a close, the pollen is committed to the wind and by it 

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

 :e afforded by several of the Khinanthaceae, as, for example, Bartsia and the 

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

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

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

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

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



Vol. n. 



69 



