CH- "] INTO NEW AREAS 13 



fruit would often be present upon the pieces carried to the trees 

 for this purpose.- The next most common plant was Samhucus 

 nigra, the elder, with 550 records; this has a fleshy fruit which 

 is eaten by birds, and the seeds subsequently dropped. The 

 third plant was Rosa canina, the dog-rose (410 records), also with 

 a fleshy fruit; the fourth Urtica dioica, the nettle (306 records) 

 with very light seeds that are easily carried by wind, but also 

 largely used in nest-making. These mechanisms were repeated 

 in the next two or three plants on the list, and then followed the 

 ash, h-raxi7ius excelsior, with 100 records. This has a winged 

 fruit, which when falling from a tree of some height during a 

 fairly strong wind may be carried to some distance; and as there 

 were many ash trees close to the river, this accounts for the 

 frequency of the occurrence of this species in the willow-tops 

 Next after this came the dandelion. Taraxacum officmale (82 

 records), with a fruit which in a breeze is easily carried upwards 

 by means of its parachute of fine hairs. By the time that we 

 come down the list to plants with 40 records, or 1 per cent, of 

 the total, 21 species have appeared there. All but one of these 

 have well-marked "regular" mechanisms, but the remaining 59 

 include a considerable number whose arrival in the tree-tops 

 must have been due to some "irregular" aid, for they have 

 neither light, winged, burred, nor fleshy fruits or seeds. Nineteen 

 of tliem showed only one record each, and their appearance must 

 be due to some such accident as having been carried in a ball of 

 eartii attached to a bird's foot, dri^-en by an unusually strono- 

 wind, or some other irregular transjDort. ° 



Classifying the records according to mechanism, we find: 



Per cent. 



Species Records of records 



Fleshy fruit (animals) 19 1763 44-6 

 Winged or feathered 



fruit or seed (wind) 33 995 25-1 



Burred fruit (animaJs) 3 631 16-4 



Light seed (Avind) ... 9 425 10-7 



Doubtful methods ... 16 117 2-9 



Thus quite an appreciable number of species are sometimes 

 transported, though in no great numbers. Of the 117 records, 

 Anthriscus sylvestris, which is used in nest-making, accounts for 

 63. 



Three important facts appear in this result: (1) that even a 

 slight barrier may produce a large effect; (2) that the bulk of 

 the individual plants (not species) travel by aid of the "regular" 



