18 Ridley .— The Distribution of Plants. 
to be absent from New Zealand and Polynesia. It is able to adapt itself to 
cold climates as far north as Finland, 69*40° N., and to the hot, wet lowlands 
of the Equator. It is known to reach an altitude of 10,000 feet in Tibet. 
It grows in wet, open spots, swamps, river banks, and watercourses, as 
well as on the sea-shore, on clay or sandy deposits with apparently equal 
facility. It is found fossil in the Cromer forest bed of the Preglacial 
Pliocene period. 
The Reed is absent from oceanic islands such as Cocos, Christmas 
Island, and Fernando de Noronha, but there is hardly any suitable ground 
for it in any of these islands, which are over 200 miles from the nearest 
mainland, though it was one of the first plants to appear in Krakatau after 
the destruction of the flora by the eruption in 1883, Dr. Treub having 
found it there in 1886, where it was one of the first fourteen flowering plants 
to appear. Sumatra and Java, the nearest land from which it could come, 
are twenty-three to twenty-five miles away, and there is no doubt that the 
seeds were blown from there by the wind. Besides its dispersal by wind, the 
plumed fruits may perhaps be borne about by adhesion to the feathers of 
water-fowl or small birds nesting in the reed-brakes, many of which fly long 
distances. Like most grasses, the Reed is wind-fertilized and does not 
require the use of insect pollinators. 
Here we have a plant possessing the greatest adaptability to soil and 
climate—only requiring sufficient moisture for its growth—and a good 
dispersal mechanism, though apparently for comparatively short distances, 
the two most important qualifications for wide dispersal. It does not 
appear as a fossil earlier than the Pliocene, though of course it may be older, 
and it is not by any means a primitive form of grass, but in the matter of 
dispersal throughout the world it has far outdistanced any of its contem¬ 
poraries of the Pliocene beds. 
Cynodon dactylon , Linn., is another grass of remarkably wide distribution. 
It ranges from Studland Bay, in Dorset, and Marazion, in Cornwall, all 
through southern Europe, as far north as North Germany, all over Africa 
and the warmer parts of Asia, Australasia and Polynesia, and Northland 
South America. It has been suggested that it has been introduced to 
England in ship-ballast, but I see no evidence of this, as it does not occur 
with ballast plants in any other localities. I have seen it in both of its 
• English habitats, one of which, Studland Bay, has never been a port and 
contains other Mediterranean plants, e. g. Polypogon mo?tspelicnsis , which 
do not grow on the beach. It may be to some extent a sea-dispersed 
plant, but it is difficult to see why it is confined to those two localities, and 
does not occur occasionally in other maritime spots. It prefers sandy 
ground, but is not a beach plant, and if planted in a clay soil soon dis¬ 
appears. In some localities it may have been introduced by man, possibly 
in foreign grass seed, as it has occasionally occurred temporarily as an 
