WIND-POLLINATED PLANTS 



71 



tion are also found in all the Grasses, Cyperaceae and Juncaceae, and in species of 

 the genera Potamogeton, Triglochin, Rumex, Chenopodium (?), Plantago, Littorella, 

 Hippuris, Myriophyllum, and all the Gymnosperms. 



Kerner ('Nat. Hist. PI.,' 11, p. 129) was the first to call attention to the fact 

 that some flowers otherwise possessing well-marked entomophilous characters, are 

 at times wind-pollinated. Some of the Rhinanthaceae and Ericaceae, according 

 to him, are insect-pollinated during the early part of their flowering period, 

 but wind-pollinated later on. The flowers of Bartsia, Lathraea, Calluna vulgaris, 

 and Erica carnea, are so constructed that when the flowers have just opened, 

 a dispersal of the pollen by wind is impossible ; at this time, during fine weather, 

 the flowers are visited by numerous nectar-sucking insects, which effect crossing. 

 ' Later on the arrangement is precisely the opposite ; the supply of nectar is 

 exhausted, and insects stop away. But, on the other hand, the filaments elongate 

 considerably, so that the anthers are pushed out of the opening of ttie corolla, 

 the pollen contained in them is discharged, and at the proper time conveyed by 

 the wind to the stigmas of younger flowers. The study of these plants conveys the 

 impression that a second apparatus is prepared lest the first should fail, so that 

 in any case the object of flowering may be attained, and this is in fact necessar}'. 

 For it may easily happen that owing to unfavourable weather the visits of insects 

 may for a long time be few in number, or fail altogether. In such cases, in 

 most plants, provision is made that flowering may not take place in vain.' (Kerner, 

 op. cit.) 



F. Hildebrand (Ber. D. bot. Ges., BerUn, xv, 1897) drew similar conclusions 

 from the study of species of Cyclamen. These also are successively adapted for 

 pollination by insects and wind. In the first (entomophilous) floral condition, the 

 pollen-grains of the cyclamens are made sticky by an oily covering, but later on (in 

 the anemophilous condition of the flowers) they become powdery, as the stickiness 

 of the oil disappears. 



True wind flowers become more numerous as regards individuals and species with 

 increasing exposure of their habitat to the wind. As I have proved in my work, 

 'Blumen und Insekten auf den Halligen ' (p. 11 [51]), the anemophilous plants 

 of the German flora constitute about 21-5% of the whole, those of the flora of 

 Schleswig-Holstein about 27%, while those of the Islands Rom, Sylt, Amrum, and 

 Fohr, which are exposed to the constant west winds from the North Sea, and to 

 the westerly storms that rage over them, amount to 36-25 %. On the Halligen, 

 small, flat, crowded, marshy islands, that at ordinary tides project little more than 

 a metre above the level of the North Sea, and over which the wind rushes 

 unceasingly without finding anything to resist it, the proportion of anemophilous 

 flowers even rises to 47 %. The above rule was confirmed by my investigations 

 of the floral arrangements of the plants of Heligoland. On the west side of 

 the high land, which is most exposed to storms, wind-pollinated plants are dominant, 

 while on the eastern declivity of this region, which in parts lies 20-24 metres lower 

 than the western margin, insect-visitors find a certain amount of shelter from the 

 raging westerly storms, and consequently entomophilous plants occur here in greater 

 abundance, while anemophilous species are less numerous (of Knuth, ' Bl. u. Ins. auf 

 Helgoland,' p. 5 [26]). 



