112 
L. Cockayne 
presence of hybrids, apart from the power of cross-pollination, is 
the occurrence of related species side by side. In this relation there 
is every transition from species which nearly always grow together 
to those which never, or very rarely, do so owing frequently to their 
belonging to different altitudinal belts, or plant-associations, or to 
their extreme rarity. Another class of hybrids occurs where one of 
the parents is confined to some particular, perhaps unusual, habitat 
into which the other parent of wider range and ecological capabilities 
has penetrated. Or both parents may be confined to a quite small 
area, and a particular habitat, where they hybridise so freely that 
there is a continuous chain of intermediates between the extremes, 
in which case floristic botanists generally, and without hesitation, 
define the group as a “variable species.’’ All the above cases refer 
to the primitive plant-covering. It is the fact of considerable hybridi¬ 
sation taking place in a virgin vegetation which is a leading motive 
for this paper. But the effect of settlement is also an important matter. 
It was only some eighty years ago, that agriculture commenced to 
modify substantially the natural physiognomy of the landscape, but 
during those few years surprising changes have come about. Associa¬ 
tions both of indigenous and introduced plants, and combinations 
of the two—some with quite a primitive stamp—have come into 
being and occupy wide areas. In these man-induced associations a 
few species have found more opportunities for crossing than formerly, 
so that their hybrids are now far more numerous than in primeval 
New Zealand. To the powerful effect of man in unconsciously 
favouring hybridisation Professor Aug. Henry has recently called 
my attention in a valued letter which I should have greatly liked to 
have published, but, of course, this cannot be done without his per¬ 
mission. It will be seen in some of the cases considered below that 
his ideas receive strong support. 
Under the next head a brief account is given of certain 
hybrids. For sake of brevity little is said about their taxonomic 
characters. Where it is stated that the hybrids are “inter¬ 
mediates,” it is meant that there is a blending of the parental 
specific characters. But many hybrids in a series may possess 
the characters both blended, or unchanged, or characters may be 
absent. 
Special details. The following classification is based upon the 
relative opportunity which their distribution (latitudinal, vertical and 
ecological) affords for pairs of species to come together. Certainly, 
as crossing experiments have shown for plants in general, and even 
