123 
Hybridism, in the New Zealand Flora 
Perhaps the maximum of multiplicity of forms is reached in the 
case of the shrub, or low tree, Leptospermum scoparium, at times also 
prostrate and even turf-making. Within a space of a few dozen 
square yards I have seen no two plants alike, and some so distinct 
they might pass for different species. On the other hand, in certain 
sphagnum bogs the individuals showed considerable uniformity, and 
in the North Auckland Botanical District the var. incana remains 
pure in groups throughout considerable areas. But frequently the 
number of forms is so great that it is impossible by means of field- 
observations to get any idea of the genetic constitution of the 
Leptospermum population. There are many other ultra-polymorphic 
species and those interested can readily find such by consulting the 
Manual. 
Many of these polymorphic aggregates have greatly extended 
their area by the aid of man. Again Professor Henry’s theory re¬ 
ceives strong support. In the slightly wetter part of the arid North 
Otago Botanical District are hundreds of acres of varieties and 
hybrids of species of Accena; Leptospermum scoparium thickets have 
increased to an astonishing extent since the settlement of the 
country; draining lowland swamps has brought into being dense 
crowds of polymorphic individuals of Phormium tenax ; many forms 
of Danthonia pilosa have replaced tussock-grassland, or even arti¬ 
ficial pasture of European grasses; the story of the incoming of 
Cassinia lowland shrubland has been already told, but in the 
montane and lower subalpine belts C. Vauvilliersii, C. albida and 
C. fulvida var. montana have made close thickets of an infinite variety 
of forms. Thus, without citing more examples it is clear that the 
new conditions have aided the crossing of varieties in no small 
degree. But what remains of primitive New Zealand can also still 
show much varietal hybridism, as in the following genera, to 
cite merely a few: Poa, Uncinia } Nothofagus, Ranunculus , Mida 
(Santalum of the Manual), Colobanthus, Pimelea, Epilobium, Draco- 
phyllum, Gaultheria , Veronica, Coprosma, Olearia, Celmisia and 
Senecio. 
There are other interesting matters connected with varietal 
hybridism in New Zealand, but, for the present, the above brief 
account must suffice. What I would particularly emphasise is, that 
the polymorphy of species cannot be explained by the self-evident 
assertion that they are “variable.” The study of varietal hybrids is 
fundamental for taxonomic advance. Field observations undoubtedly 
have an important place in such work, but experiment must play 
