332 
THE COTTAGE GARDENER AND COUNTRY GENTLEMAN, Maech 5, 1861. 
sufficiently known. It is tlie excitement occasioned by 
the access of the sun that makes such plants liable to 
injury ; and a south aspect, whether in summer or winter, 
is prejudicial to them. I believe that the covering of a 
pent roof in a northern aspect without any flue is more 
congenial to those plants than a greenhouse, with caution 
to prevent any heavy rain or snow from being driven 
upon them by a strong north wind, which is easily 
done.” 
These ideas and suggestions were published by Dr. 
Herbert in 1886, as just stated, in a standard work on 
the Amaryllidacete, which found its way into all the 
natural-history libraries and museums in Europe and 
America. They were quoted since in all our gardening 
books and periodicals, and they now form the ground 
books of M. Naudin’s pamphlet on “geothermal culti¬ 
vation.” He agrees with Dr. Herbert as to “the growth 
in our climate of plants from warmer countries in the 
open ground, and without protection [in summer], not 
merely a sufficient atmospheric temperature, but bottom 
heat as well.” And he recommends the very same means 
for giving this bottom heat, and for covering the plants 
in winter, as were given in the “ Amaryllidaceas ” by Dr. 
Herbert—that is, “ by artificially heating the soil, so 
long as its natural temperature is insufficient, by means 
of flues or hot-water pipes.” But “it still remains to 
put the stem and branches beyond the reach of frost in 
winter.” This he proposes to do, in Dr. Herbert’s words, 
in a pent or tent roof of some textile fabric; and the 
south side to run up and down, so as to give light and 
air to the plants in mild weather. “A framework of 
wood, simple, light, and strong—a sort of cage which 
would pull to pieces and be easily put together again— 
would serve to support the protecting materials; in 
short, it would be merely a tent to secure the plants from 
cold ’’—such as, for instance, Lady Granville used thirty 
years since at Dropmore, and others after her, while 
the foolish rage for “ acclimatising ” plants was prevalent 
in Britain. “Bush mats would suffice for the sides, and 
the more pliable materials should be reserved for the 
top. It would be necessary to cover the whole with a 
tarpaulin reaching to the ground, which, by thicken¬ 
ing the covering, would render it more effectual, and 
at the same time protect it from the effects of moisture,” 
which Dr. Herbert dreaded so much in such experi¬ 
ments. 
The scientific reasonings and practical observations of 
M. ISTaudin on the subject of his pamphlet are all very 
good, except the one on which the whole scheme turns— 
the practical part, and that reveals M. Naudin as a com¬ 
plete theorist; and any one here or in Paris, who will 
follow his directions to the letter in the winter manage¬ 
ment of a pent-up structure, will be as sure to fail with it 
as Louis Philippe failed to keep on the throne of France. 
He says, “ The soil in which the trees are planted should 
be isolated from the adjoining ground, and heated bv 
flues or hot-water pipes.” This “ isolated ” is the one 
point in which M. Naudin differs from Dr. Herbert, and 
means (if it is meant to have a meaning), that the bed is 
to be separated from the bottom or subsoil, as we separate 
Vine-borders on arches or on flags of stone, in order to 
get bottom heat for the roots. Then “ the tents should 
be made as close as possible during severe frost; and if 
the temperature of the interior descend to near the 
freezing-point, the soil should he moderately heated, so as 
to maintain the air of the tent above 32° '” ! ! ! Now, 
“ believing,” as does one of my friends and fellow- 
labourers in explaining practical cultivation, “that M. 
Naudin’s suggestions may be successfully acted upon as 
regards many plants with which our greenhouses are at 
present overcrowded, and this with the severity of the 
weather in last December still fresh in our memory,” I 
would ask to what degree of heat should the dry soil of 
the beds for geothermal gardening—say beds 20 inches 
deep how hot must the dry soil be kept to prevent the 
“ frigorific pulsation ” of meteorologists descending on 
the head of plants 4 feet above the surface of the “ heated 
soil?” Or, say, the isolated bed of soil is only 1 foot 
deep—is there a man on this side of the Channel, or on 
that, who will say that the lower stratum of the soil, in 
which the best of the roots are, must not necessarily be 
as hot as would roast Potatoes, before the upper surface 
of the bed is sufficiently warm to repel the frost from 
the stems and branches, which are within 4 feet of the 
ground, to say nothing about the fate of such as are 
higher from it ? The idea could never enter a practical 
mind—the thing is wholly preposterous, and will never 
do. As in the smallest greenhouses, and in the little cold 
and hot frames of the present practice, you must not 
trust to or try your means for bottom heat in “ geothermal 
cultivation ” for the supply of top heat in the same house, 
frame, or tent. There must be branch-pipes or branch- 
flues to keep the air to the proper standard, without ever 
having recourse to those which supply the bottom heat. 
Geothermal culture has been well tried, and is undoubtedly 
understood by British gardeners. Our conservatory walls, 
and the rage for acclimatising plants formerly, have 
left nothing to be decided on respecting it among our 
gardeners. 
We hail with satisfaction such attempts at reviving 
sound practical ideas which are of long standing amongst 
us, like this by M. Naudin; and any one who will give 
us the means, the hard siller, to set the thing in motion 
will have nothing to risk in finding out the surest way 
to success. The subject is already ripe with us, and at 
our fingers’ ends. We shall not risk or destroy a root, 
or spend a shilling more in fire than is actually necessary. 
In the most extreme case—say when we have stove bulbs, 
as Crinums and such plants, under geothermal culture, 
we shall not use the flues or pipes which are laid for the 
bottom heat oftener than once in three weeks or a month 
from October to April. 
To keep the air of the pent-house above the freezing- 
point, we must use the same styles of heating which we 
do now for greenhouses, and not attempt with M. Naudin 
to heat the soil from below ; for that would burn up and 
destroy every root in the bed of soil, ere the soil could 
be heated to the necessary degree—if, indeed, a bed of 
dry soil could be heated at all. From the middle of 
April to the end of August, the underground pipes or 
flues would be worked as Dr. Herbert recommended, 
just to keep the heat of the soil to the required degree 
and no more, as is done at present where Vine-borders 
are isolated from the subsoil and heated from below. 
But, for the sake of argument, suppose the roots at the 
bottom of the bed of soil could bear a heat of 200° with 
impunity, the heat of a hot-w ater pipe at work in a green¬ 
house is often at that point of heat in hard weather, and 
when the quantity of piping is barely sufficient to work 
the house; and suppose that the winter is the time for 
resting the plants that are under geothermal culture—is 
that not the right time to have the soil in that state 
which we term neither wet nor dry, and at the lowest 
point of bottom heat P and is it when the soil is in the 
driest state, and at the coolest degree that any mortal 
being should think of applying bottom heat to a bed of 
soil to keep out the frost ? It is even so ; for M. Naudin 
puts the plan plainly before our faces in black and white, 
and we are so taken with the fashions of Paris on this side 
of the Channel, that some of us here “ believe such sug¬ 
gestions may be successfully acted upon.” And if that 
is not grafting at the wrong end of the stock, it must 
be bottom heat with a vengeance. Nevertheless, geother¬ 
mal cultivation apart from M. Naudin’s way of bottom¬ 
heating it, and on the principld*of heating Vine-borders, 
deserves all the spirit there can be enlisted in its favour 
by urgent writing and by all the arts of persuasion. It 
is one of those schemes which are sure to pay in fruit as 
much as in flowers ; and if I am spared till they can fin d 
me room in these pages, I shall give you the results of 
