132 
POPULAR SCIENCE REVIEW. 
fact, that thousands of acres in each of these countries are co- 
vered, year after year, by crops of the same plant, introduced 
from one to the other ; and by annually increasing numbers of 
trees, shrubs, and herbs, that have either run wild, or are suc- 
cessfully cultivated in each and all of them. The third pro- 
position follows from the two others, and of this the best example 
is afforded by a good garden, wherein, on the same soil and 
under identical conditions, we grow, side by side, plants from 
very various soils and climates, and ripen their seeds too, pro- 
vided only that their fertilization is insured. The Cape gera- 
niums, London pride and Lysimachia nummularia in our London 
areas, the pendent American cacti in the cottage windows of 
Southwark and Lambeth, are even more striking examples of 
the comparative indifference of many plants to good or bad 
climate and soil ; and what can be more unlike their natural 
conditions than those to which ferns are exposed in those in- 
valuable contrivances, Ward’s cases, in the heart of the city? 
True, the conditions suit them well, and with respect to 
humidity, and equability of temperature, are natural to them ; 
but, neither is the absolute temperature, nor the constitution, 
nor freshness of the air, the same as of the places the ferns are 
brought from ; nor is any systematic attempt made to suit the 
soil to the species cultivated, for, as Mr. Ward himself well 
shows, the arctic saxifrage, the English rose, the tropical palm, 
and desert cactus, live side by side in the same box, and under 
precisely similar circumstances, and, as it were, in defiance of 
their natal conditions. 
Let it not be supposed that we at all underrate such power as 
soil and climate really possess. In some cases, as those of chalk, 
sand, bog, and saline and water plants, soil is very potent ; but 
the number of plants actually dependent on these, or other 
peculiarities of the soil, is much more limited than is supposed. 
Of bond fide water-plants, there are few amongst phsenogams. 
Sand plants, as a rule, grow equally well on stiffer soils, but are 
there turned out by more sturdy competitors ; and with regard 
to the calcareous soils, it is their warmth and dryness that fits 
them, to so great an extent, for many plants that are almost con- 
fined to them, or are absolutely peculiar to them. So, too, with 
regard to temperature, there are limits, as regards heat, cold, 
and humidity, that species will not overstep and live ; but, on 
the other hand, so much has been done by selection in procuring 
hardy races of tender plants, and so much may be done by re- 
gulating the distribution of earth-temperature, &c., that we 
already grow tropical plants in the open air during a portion of 
the year, and eventually may do so for longer periods. 
Amongst the most striking examples of apparent indifference 
to natural conditions of soil and climate, I would especially 
