PERSISTENT JUVENILE FORMS. 69 
are eminently plastic, certain of their organs—or, indeed, the whole 
plant—responding to change of environment. Thus the beautiful 
ramarama (Myrtus bullata) when exposed to the sun has its leaves 
greatly blistered and stained with red or purple, but when suffi- 
ciently shaded, as in thick forest, they are almost smooth and quite 
green. More remarkable still are those shrubs or trees now to be 
dealt with, but all too briefly, which have a juvenile form not only 
distinct from that of the adult, but which persists at the former 
stage for a long time, even for many years. 
The number of New Zealand seed-plants which differ in a more 
or less striking degree at various stages of their growth according to 
the age of the individual is about 200, belonging to 32 families and 
53 genera. In about one-half of the above the actual growth-forms 
of the juvenile and adult are different—z.e., they are adapted for 
conditions more or less different. With the exception of three or 
four species, the plants which exhibit this remarkable phenomenon 
are endemic, while of the endemic genera no fewer than ten possess 
species of the above character. Nor is this all: certain species 
which exhibit the phenomenon in New Zealand do not do so else- 
where. There appears, then, ground for a shrewd suspicion that this 
state of affairs is connected in some way with New Zealand itself, 
and may be referred to conditions of the past provided by changes 
in the land-surface and the climate. This appears the more likely 
since certain strongly marked juvenile forms appear rather out of 
place at the present time. There seems, for instance, no reason 
for the great differences between the young and adult forms of the 
New Zealand jasmine (Parsonsia heterophylla). (See text-fig., p. 54.) 
If the growth-forms of the above class of plants be analysed it 
appears that 48 are trees, 114 shrubs, 13 herbs, 6 water-plants, and 
19 climbing-plants These estimates could easily be made higher 
if distinctions somewhat slighter were recognized From the stand- 
point of their water-requirements, the juvenile state of 125 is less 
tolerant of drought than the adult, in 16 it is able to bear drought 
better, and in 59 there is no striking difference. 
The most important cases are where the juvenile stage not only 
remains juvenile for many years, but actually flowers and bears fruit. 
This has been observed in no fewer than 19 species. Thus the kai- 
komako (Pennantia corymbosa) remains in its young state for many 
years as a divaricating shrub. Finally it grows into an ordinary 
