246 Notice of Dr. Hooker’s Flora of New Zealand. 
vere in supplying the original conditions ; and it is most difficult of all 
this, whether we take such plants as 
aid of man (as Sonchus oleraceus, Callitriche, and Montia) through 
‘all latitudes from England to New Zealand; or such as have. within 
modern times followed the migrations of man (as Poa annua, Phalaris 
Canariensis, Dock, Clover, Alsine media, Capsella bursa-pastoris, and 
a host of others); or such as man transports with him, whether such 
temperate climate plants as the cerealia, fruits, and flowers of the gar- 
den or field, or such tropical forms as Convolvulus Batatas and yams, 
all these, in whatever climate to which we may follow them, retain the 
egree. — i 
ith comparatively few exceptions, plants are confined within 
not the case. : 
. A multitude of allied species of plants grow close together wit 
out any interchange of specific character; and there are instances 
exceedingly closely allied plants keeping company under many moe! 
cations of climate, soil, and elevation, yet never losing their distinctive 
h- 
of 
6. One negative argument in favor of distribution from one centre 
only, is, that taking the broadest view of the dispersion of ape 
find that the more extensive familiest are more or less widely distri0U- 
rul 
whose facilities for dis are proverbial, are amongst the most local; and th 4 
same may be said of Ligeetiind and Solanew, whose ads retain their vitality 
a remarkable degree: a few of their species are remarkably cosmopolite, but “ia 
greater number have generally narrow ranges, 
