267 
or organic substratum, light, and a chemical stimulus (probably 
that provided by cellulose), Other authors have urged the impor- 
tance of moisture or even liquid water for germination. 
The explosion which accompanies the destruction of the fruit 
will shoot the seed some 30 to 40 ft., but some other cause must 
account for the wide and discontinuous distribution of Arceutho- 
biwm Oxycedri. There is no evidence that the fruits are eaten by 
birds, but the possibility of an exploding fruit hitting a bird 
must be considered. The likelihood of this happening is decidedly 
increased by the fact that the jerk of a bird alighting on a slender 
branch would cause all the mature fruits near to explode and to 
scatter their seeds in all directions. Many species of birds are 
widely spread in the Mediterranean Region, and the long migra- 
tions of some species would enable them to transport seeds stuck 
to them for great distances. Thus, a colony of the Yellow Wagtail 
(Motacilla campestris), is found from South-East Russia to 
Turkestan in summer, and winters in South Africa. The chances 
seem in favour of such a bird now and again getting a sticky seed, 
such as one of Arceuthobiwm, stuck to its feathers and getting rid 
of it either en route or at its destination. That Arceuthobium 
is not more widely distributed by this means is probably due to its 
dependence on a narrow range of host-plants and on certain con- 
ditions for germination, but it is difficult to see how its spread 
to Tropical Africa can be otherwise explained. Warming, *‘ Botany 
of the Faeroes,’’ pp. 676-678, gives very strong evidence against 
birds acting as regular fruit and seed dispersal agents over long 
distances, but it is to be noted that the observations quoted were 
all made in the colder North Sea area, and in any case do not 
eliminate the possibility of occasional transport by birds from one 
country to another. As regards the discontinuous distribution of 
the genus Arceuthobium in the North Temperate Zone a classifi- 
cation of it with the ‘‘ Tertiary Relicts ’’ which are so conspicuous 
a feature in any analysis of European vegetation is suggestive. 
However, from what has been said above, it seems more reasona ble 
to think of Arceuthobium Oxycedri with its distinctive method of 
seed-dispersal apart from the majority of such Tertiary relicts as 
Forsythia, Ramondia, etc., and to conclude that it owes its 
bium in intermediate localities, perhaps on the junipers of 
Eritrea, Somaliland, Abyssinia or South Persia. 
That Arceuthobium Oxycedri is not alone among Mediterranean 
plants found on Tropical African mountains 1s evident from a 
study of their flora. Thus, Engler, in a paper in the Annals of 
Botany, vol. xviii. p- 523 (1904), records the following species or 
genera with closely allied species which occur th in the 
Mediterranean Region and in Tropical Africa: Luzula, Anthoxan- 
thum, Koeleria cristata, Arabis, Subularia, Stenophragma Thalia- 
