868 THE DISPERSION OF SPECIES BY MEANS OF FRUITS AND SEEDS. 



water-fowl when they migrate neglect their usual habit of assiduously removing all 

 traces of dirt, and we know from the investigations made by Darwin how great is 

 the number of seeds imbedded in the mud. From 6f ounces of mud 537 plants 

 germinated. In my own case the examinations of the mud obtained from the 

 beaks, feet, and feathers of swallows, snipe, wagtails, and jackdaws resulted in about 

 half as productive a yield of fertile seeds; but that is a sufficiently striking result; 

 and when it is remembered that pigeons and cranes traverse from 60 to 70 kilo- 

 metres in an hour, whilst swallows and peregrine falcons cover as much as 180 

 kilometres, it is clear that fruits and seeds affixed to these birds may be carried in a 

 very short time over several degrees of latitude. The number of species of plants 

 which are dispersed in this manner is, it is true, but small. For the most part they 

 are water-side and of these chiefly small annual species, as is evident from the 

 following list of those whose fruits and seeds I found most frequently in the mud 

 taken from birds: 



Centunculus minimus. 

 Cyperus ßavescens. 



„ fuscus. 

 Elatine Hydropiper. 

 Erythrcea pulchella. 

 Glaux maritima. 

 Glyceria fl uitans. 



Heleocharis acicularis. 

 Isolepis setacea. 

 Juncus bufonius. 



„ compressus. 



„ lajnprocarpus. 

 Limosella aquatica. 

 Lindernia pyxidaria. 



Lythrum Salicaria. 

 Nasturtium amphihium. 



„ palustre. 



„ sylvestre. 



Samolus Valerandi. 

 Scirpus maritimus. 

 Veronica Anagallis. 



Most of these species are distributed over all parts of the world, but they seldom 

 remain for a long time in any particular locality. They often start up quite unex- 

 pectedly at places where migrating birds have rested and gone to drink. The 

 extraordinary occurrence on the edges of ponds in Southern Bohemia of the tiny 

 Coleanthus suhtilis, which is indigenous to India, and the sudden appearance of 

 the same species of grass in the West of France about twenty years ago may be 

 unhesitatingly attributed to the mode of dispersion in question, as may also the 

 occurrence of the tropical Scirpus atropurpureus on the shores of the Lake of 

 Geneva and that of the Southern native Anagallis tenella on the shores of the 

 Schwarzsee at Kitzbühel in North Tyrol. 



The instrumentality of rain-soaked earth on steppes, on ploughed fields, and on 

 roads in sticking numbers of fruits and seeds to animals' feet, whether the latter be 

 in the form of hoofs, claws, or toes, or to their hair or feathers, as the case may be, 

 has been the subject of repeated investigation. In the hardened earth taken from 

 the feet of birds Darwin found a large number of seeds, of which many germinated. 

 Many weeds which grow on fields and roadsides {Prunella vulgaris, Malva rotun- 

 difolia, Potentilla anserina, P. reptans, P. sujnna, Ranunculus sardous, &c.) 

 depend mainly on this mode of dispersion. According to an informant, the suckers 

 of the Gecko (a kind of lizard adapted to running about on smooth rocks and walls) 

 are sometimes beset with fine seeds, and there can be no doubt that certain plants 

 may be disseminated by such means over steep declivities of rock. 



The excretion of sticky substances by fruits and seeds themselves must naturally 



