224 
THE GARDENING WORLD . 
March 18, 1905. 
\Ve may state, however, that it maintains this colour after 
ascending the mountains to considerable elevations. 
One of the divisions of the book is termed “ Retrograde 
Varieties,” and in the chapter devoted to the characters of such 
varieties he says everyone admires the luxuriance of garden 
flowers and their diversity, but that the history of many of 
our garden flowers is so obscure that their hybrid origin is 
forgotten or unknown. The Pansy is mentioned as a good 
instance of this. We have seen Pansies in gardens that practi¬ 
cally were in no way distinct from wild forms and—these occur¬ 
ring in neighbourhoods where the true V. tricolor was rare or 
unknown—the conclusion Avas forced upon us that they were 
reversions from garden types through a number of generations. 
This same fact may also be noted in cottage gardens, and 
possibly other gardeners have also noted the same fact. In a 
Avestern suburb of London we have seen a Pansy with small 
blue-purple and yellow flowers that might easily have been 
matched by Avild types from the north. 
The Professor, however, states that in systematic botany a 
species cannot be described by the presence of any single 
character, but that its limitsi are defined by the sum total of 
characters, which may vary in actual number, but always con¬ 
sist of several. A variety derived from this by retrograding 
would be a seedling that had lost one of the characters of the 
type, while a variety of another kind would be that which had 
developed something additional. 
A very good definition he gives is that a variety which loses 
one of the characters of the parent plant would be regarded as 
one arising by a negative change or mutation. On the other 
hand, those forms which add another character to that existing 
in the parent would be described as a positive mutation. These 
various types may be illustrated by reference to some of the 
British plants indicated in this work. 
The flower-head of a composite is made up of ray florets and 
disc florets, usually both present in the same head, though 
sometimes the ray may be normally absent in any one par¬ 
ticular species, or absent in another form usually regarded as 
a variety. In Matricaria Chamomilla both the disc and the 
ray florets are present. In another form known as M.C. dis- 
coidea, the ray is always absent. This is stated to spread very 
rapidly, particularly in France, Norway, and North America, 
having been introduced to the latter country. We may say 
also that it is remarkably common in some districts in this 
country 500 or 600 miles apart. The lack of the ray would be 
considered a retrograde change, but the result is a plant that 
is remarkably constant even in a natural state, or A\dien ex¬ 
periments are made under scientific cultivation or experiment. 
Other examples of this negative change may be found in 
Aster Tripolium, Centaurea nigra, and the common Camomile. 
The latter also gives a positive form of mutation by the pro¬ 
duction of double flowers having a much larger number of 
ray florets practically filling up the head. Another form of 
negative change occurs in blue-purple or red flowers, Avliich 
give rise to albinos or white varieties. We have found an 
immense number of such albinos amongst British plants. 
The author gives positive forms of mutation amongst plants 
varying solely or chiefly in colour. Plants haAdng normal 
AA'hite floAvers are represented by the white Campion, Milfoil, 
Begonia semperflorens, the common Hawthorn, and Bobinia 
Pseudacacia. All of these occasionally give red or pink varie¬ 
ties, which have the advantage of colour that did not exist 
in the parent forms. Nothing seems to escape the author in 
tracing out his theories, for he gives instances of the acquire¬ 
ment of fresh characters even in fruits. For instance, the black 
Oat possesses that colour simply by the development of a 
greater amount of red pigment. The blood-red Orange of 
Malta and red and yelloAv Gooseberries are also varieties hav¬ 
ing the positive form of mutation by having something 
which the parents did not possess. Turning to leaves, he says 
that certain varieties of trees and shrubs have acquired addi¬ 
tional character in the matter of foliage having purple leaves : 
instances of this are the purple-leaved Peach, purple Hazel, 
purple Beech, purple Birch, purple Barberry, and several 
others. There are also numerous purple or other coloured 
herbaceous plants, including the Avhite Clover, the brown 
Lettuce, and the garden Coleus, in AA’hich the number of addi¬ 
tional colours is remarkable. 
In tracing out varieties of a negative or retrograde form of 
change, he gives a great variety of subjects differing in 
various respects according to the kind. The Feather Hyacinth 
is a case in Avhich the whole flower is retrograde or negative, 
the parts of the flower being represented by coloured bract-like 
leaves. He also introduces seedless plants or fruits, to show 
this retrograde change in certain subjects. For instance, there 
are seedless Bananas, Pineapples, Ajaples, Pears, Grapes and 
Oranges. Not quite the same type is the stoneless Plum of 
Burbank, in which the bony inner wall of the fruit popularly 
termed the stone is absent, so that the pulpy mass comes in 
direct contact with the kernel. 
Quite of another kind is the smooth Peach or Nectarine, as 
it, is usually termed. In this instance the doAvny coat of the 
Peach has disappeared, leaving a smooth fruit. Numbers of 
Nectarines have been proved to have arisen from an equal 
number of races of Peaches, and to show that they are actually 
inter-related he reminds us of the fact that a Peach tree does 
sometimes give rise to Nectarines by bud variation on the 
same tree and vice versa. 
His explanation of the phenomena of weeping and fastigiate 
trees is interesting. Weeping trees, of avhich he mentions a 
number of species which have given rise to them, owe their 
drooping or pendent habit to the length and weakness of their 
branches. In this condition they are unable to resist the 
action of gravity, and thus hang toAvards the earth. The con¬ 
trary arises in those trees which produce upright varieties, 
such as the Lombardy Poplar, the fastigiate Oak, Robinia, and 
the Irish Yew. In the ordinary Yew the primary stem is 
upright with the leaves equally distributed round the axis. 
The branches have their leaves in practically tAvo rows, but 
in one plane. The Ir ish Yew has diverged from these bA r practi¬ 
cally converting, so to speak, its branches into stems, so that 
they are upright with the leaves distributed equally around 
them. Owing to the acquirement of some character which 
gives the branches this rigidity, gravitation is unable to react 
upon them in the usual Avay as is customary in the normal 
type. 
In speaking of stability and atavism, he introduces many 
of his experiments to show that certain varieties are remark¬ 
ably constant, and reproduce themselves practically constantlv 
without retrograding.- One of these plants was the discoid 
AUiriety of the common Camomile, in which he raised between 
1,000 and 2,000 seedlings, AAdiile every individual, weak and 
strong, reproduced the characters of the parent. He could 
find no trace of atavism or reversion to its supposed ancestral 
type. 
There is a weed in this country knoAvn as Bidens cernua, 
Avhich has only disc florets, but on the Continent there is a 
form which produces rays. From this plant he raised between 
2,000 and 3,000 individuals, and when they came into bloom 
every one of them possessed rays, although it Avould be one of 
the cases of positive mutation. Many other species of com¬ 
posites furnished him with similar cases of stability. Amongst 
garden plants he mentions white Currants, AA'hite Strawberries, 
and white Grapes, which reproduce themselves true to char¬ 
acter when raised from seeds, so that in this respect they liaA’e 
all the stability of a species. Strawberries without runners 
originated over a hundred years ago, and have continued to 
reproduce themselves without runners. A real case of rever¬ 
sion occurs too in the white variety of the flowering Currant 
(Ribes sanguineum), which sometimes reverts to the ordinary 
red flowered type. This is evidently a form of reversion 
Avhich takes place in the bud similar to the case of sporting 
amongst Chrysanthemums. 
An interesting chapter is that on pistillody in Poppies, in 
which more or less all the inner series of stamens are con- 
verted into ovaries more or less perfect. This may frequently 
be met with in the Opium Poppy as cultivated in gardens. 
The author says he has found these accessory small heads 
varying from 50 to 100 as a rule, but. in extreme instances he 
has found 150 of them or more seated around the principal 
seed vessel. Not only so, but occasionally some of these ac- 
