352 
THE GARDENING WORLD, 
April 29, 1905. 
though the surrounding air contains no frost- whatever. On 
clear, calm nights this evaporation is more active than 
on any other, arid when the sky is overcast there is no evapora¬ 
tion, because the air is practically saturated with moisture. 
Hence the reason why the effects of “ La Lune Rousse " were 
never noted when such conditions existed, and not, as the 
people believed, because the moonshine was obscured. 
\ eiy pretty experiments can be made showing the effects of 
rapid evaporation by chemical agents. By pouring some 
spirits of wine on the skin a decided feeling of coldness will 
be experienced, and the liquid will have shortly disappeared. 
We say this has been absorbed by the skin ; on the contrary, 
it has evaporated into the air, and the evaporation has been so 
rapid as to partially chill the spot upon which it was poured. 
If gasolene, which is still more spirituous, in like manner is 
poured on a piece of sponge or dry sphagnum moss, the 
evaporation is , so rapid as to convert these materials into 
masses of solid ice. In spring, the air on clear, calm nights 
has- rarer atmospheres than at any other time of the year, 
and evaporation is much greater, and when the foliage is so 
tender the consequent evaporation may be so great as to freeze 
it, though the surrounding air is some degrees above' freezing 
point. D. C. 
Degeneracy of Varieties Propagated from 
Buds. 
Do Potato Stocks Deteriorate 1 
The following communications relating to this subject have 
been received by the Scientific Committee of the Royal Horti¬ 
cultural Society : — 
Mr. Burbidge.—It is a wide question, and has been discussed 
ever since the late Thos. Andrew Knight, Esq., wrote his' 
“ Treatise on the Apple and Pear,” in 1797. It was, I believe, 
Knight’s first book, a small octavo, and is now rather rare, 
it is a common belief amongst gardeners that varieties do de¬ 
teriorate or go back in gardens. This I myself do not believe 
is true if they are well, wisely, and properly cultivated. De¬ 
terioration is very often, even if not always, the result of bad 
culture, senility, or neglect. It is, moreover, due in many 
cases to growing the same variety too long, on the same soil, 
and by the use of too much manure. With Po-tato-s this is 
especially the case ; but no Potato as a variety deteriorates 
on good soils if the seed or sets are changed, or obtained from 
a different soil and climate every year. The old Ashleaf 
Kidney Potato is as -old as most Potato®, and still one- of the 
best. The craze for novelty and competition in the trade often 
lead to good old varieties being superseded by new seed¬ 
lings or selections, or by old kinds of known excellence being 
again sent out under new names. Varieties may deteriorate 
locally, i.e., when badly grown on unsuitable soils or under 
adverse conditions, but no one can prove that varieties like 
the Black Hamburgh Grape, Royal Geoige Peach, Moor Park 
Apricot, Ne Plus Ultra Pea, General Jacqueminot Rose, Old 
Ch-ve Carnation, ever deteriorate as varieties all over the area 
of their cultivation. Did anyone ever hear of any variety 
of Banana, Pine-apple, or seedless Grape ever wearing out? Do 
Osier Willows ever wear out ? Varieties may be neglected and 
weakened by being planted too. constantly on the same soil or 
in unsuitable localities; they may also be renamed or super¬ 
seded by novel kinds being “ boomed ” over their heads, so to 
say; but no variety fairly well grown on fresh and suitable 
soil ever dies out. No one variety grows or is as productive 
"ii all soils alike; but the best varieties are ever adaptive, and 
their produce averages out tvell on all soils. 
Most of the Figs, Mulberries, and Grapes grown to-day are 
practically tho-se known for centuries. Brown Turkey or White 
Ischia Figs, the Zante Currant Grape, Black Monukka Grape, 
Bananas, Pine-apples, and other seedless fruits increased veze- 
tatively are as healthy and productive to-day as they have 
ever been. Of course, the words “ a variety ” o-ften mean 
that we are dealing with a group of distinct individuals, and not 
with a multitude of ndividuals precisely alike. Good culture, 
continual change of soil and rigid selection are all necessary 
to keep at their best “ varieties ” so-called, and under such 
conditions I do not admit that the deterioration or wearing 
out of varieties ever takes place in either gardens or in fields. 
As recently pointed out by Prof. Hugo De Vries in his “ Species 
and Varieties: Their Origin by Mutation,” in which work 
some aspects of this subject are ably dealt with, it is shown 
that any crop of either corn or roots consists of individuals of 
varying vitality or productiveness. This makes selection pos¬ 
sible. There are certain individuals in every crop, as in every 
flock or herd, that can either utilise more food than others, or 
that in ny case are more productive than are others under 
the same conditions. The simple art of selection enables the 
gardener or farmer t-o improve the best varieties or strains by 
continual selection. Some individuals in any variety or strain 
may show a retrograde tendency, and these are eliminated, 
so as to give added opportunity to the best and most produc¬ 
tive individuals, and in this manner the variety is improved 
and its life ensured. In a word, varieties are constant or ever 
improving only under the best conditions of cultivation. Bv 
the same token they will deteriorate only if neglected and 
grown under bad conditions.—F. W. Burbidge. 
Mr. Clarke.—It is a fact that the- Potato does deteriorate. 
It is not wise to grow the same stock more than two years. 
We find in this district that the further north we get our seed 
from the better it is. I noticed this year that the seed from 
Scotland produced more than the second year. It is generallv 
considered that the second year gives better results, but at 
any rate it is not wise to- grow it more than two years on one 
faim. I should not say that after being grown, say, here 
two years and then moved some miles away, that it would 
increase its vigour. It might- probably grow a-s much for two 
seasons, and then it would be exhausted. It is a good change 
from this country on to the black soils, but will not do to come 
from there to here again ; and I think that where it has been 
grown on black land the better plan is to use the seed for 
cattle or pigs, and get a fresh stock. My experience is that 
the more worn-out stocks do take the disease quicker than 
others. I am afraid that eve shall find that the newer varieties 
are very tender. I am still a great believer in the spray when 
properly applied. I think I was one of the first to take it up, 
and I well remember the opposition to it, I was in Bedford¬ 
shire, just- putting them in the way how to use it—I think in 
1894—when an old gentleman came up to. me and said : “ Mr. 
Clarke, I think you are trifling with Providence.” That was 
one instance. Now it is general ; but they are not half done_ 
hence a good deal of disappointment.—West mere, Sutton 
B) idge. 
Mi. Fraser. It- has always- been reckoned good practice in 
this district- t-o change ‘ se-e-d Potato® after a. few years, 
getting seed from a different class of soil, if not from another 
locality, boil seems to' have as much to do wi11 1 degeneration 
as climate, or more, and you must remember that round here 
we have a great variety of soils, clay that, in some seasons, 
almost unworkable, various gradations and combinations 
ot loam, sand, and gravel, beside® black, mouldy soils and 
peaty soils. We have also within this small county wide 
chfleiences of climate, including rainfall. Thus, without goinof 
far from home, we can have a decided change of locality! It 
considered desiiable to g'et seed from a higher district, which 
means a- mo-ister as well a-s a colder and later. Thus, < we 
had British Queen from an up-country farm, say, GOO feet above 
sea- level, planted last season 1 o-n light gravelly so-il on this- farm 
at between 80 and 90 ft. They did exceptionally well, but they 
were off a good farm, and were a- fine sample to begin with. 
1 otatos from a diy soil are not looked on with, favour for 
seed, and in the case of such soils it- seems to- be necessary to 
change frequently, every two or three years at least, otherwise 
the leaves grow curly and stunted, and the plant does not 
properly develop. 
Seed from Ross-shire has been found to do well in Moray¬ 
shire, but so also has seed from Forfarshire. Ross-shire has 
a considerably more moist climate than Morayshire, but not 
much cblder, if at all, at the same! elevation. The soil of Ro-ss- 
shne is, I should think, the richer in general. Forfarshire is 
agriculturally one of the finest counties in Scotland. 
