ioy 
Hybridism in the New Zealand Flora 
that my belief in the hybrid nature of certain of the groups of in¬ 
dividuals represented in the list at the end of this paper is based. 
i. The alleged hybrids should be more or less intermediate in 
character between the reputed parents, or, better still, there may 
be a graduated series of forms leading from one parent to the other. 
2. The reputed parents and their hybrids should grow in fairly close 
proximity. 3. The alleged hybrid, if fertile, should give rise to a 
more or less polymorphic progeny. 
Certainly some of these conditions, and those in footnote 6, p. 106, 
may not be fulfilled and yet hybridism be almost certain. Thus a 
hybrid may be more or less invariable; it may breed true, or produce 
offspring but little polymorphic; as a result of change in an association 
hybrid individuals of considerable age may occur, even if one or 
both parents are absent 1 , or the parents may be present and the 
hybrid wanting; in short, there are no absolute criteria, so each case 
of suspected hybridism must be decided on its merits. 
With regard to the application of the above principles in the 
field, it is clear that no absolutely conclusive proof can be given that 
any group of plants sexually reproduces itself true. Nevertheless, if 
a certain group, consisting of similar individuals differing only slightly 
according to fluctuating variation, is found in several—perhaps 
many—localities, it seems highly probable that the group in question 
is a pure strain. To be sure, such a group may vary greatly when 
in some habitat differing considerably from that where it usually 
occurs, but such environmental changes are constant characters, and 
their nature is recognisable in most cases. Such a group may be 
connected with a related group by intermediates, but only if both 
groups grow in close proximity. 
“Intermediates/’ such as those just mentioned, are considered in 
many floras an indubitable proof that the groups thus connected 
are not true-breeding entities, but that they “vary” and “run into” 
one another; therefore, such groups must be united, indeed, they are 
considered one and the same. For such an assumption, in the light 
of genetic studies, and even of field-observations, there seems not 
the slightest proof. The intermediates occur only when individuals 
of both groups grow near one another, otherwise there is no “ varia- 
1 Thus Kerner {The Natural History of Plants, translated and edited by 
F. W. Oliver, London, 1895, Vol. n, p. 592), writes of explaining “the pheno¬ 
menon that species which, from their characteristics, may be looked upon as 
hybrids of two other species, occupy in each case a district which is separated, 
and often at a considerable distance, from the areas inhabited by the species 
supposed to be their progenitors,” and specific cases are cited. 
