54 JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. t January 18, 1883. 
dined to touch zero. Looking in last week at that very interesting 
compartment, the Filmy Fern house at Glasnevin, nothing could 
look more happy than the Todeas, Hymenophyllums, and other pel¬ 
lucid beauties in their garniture of richest green, profusely beaded 
with diamond dewdrops, notwithstanding that in their cool and 
humid quarters there must have been in the previous week some 
fifteen or more degrees of frost .—(Irish Farmers' Gazette .) 
DO AQUATICS LIKE MANURE? 
This always seemed questionable to me till I saw the beneficial 
effects of good soil and culture upon some plants of Menyanthes 
found in a swamp in Ashdown Forest. Wonderful as was the 
change wrought in them by a single season’s care, yet the result 
was by no means conclusive, for mere wildings growing in an 
exposed situation amongst a crowd of other plants are unlikely to 
grow so freely or to become so robust as they do when a special 
station is given them in a sheltered pond. Last summer, however, 
the matter was settled beyond dispute : a sewage pipe burst near 
the pond containing the principal collection of aquatics, and the 
sewage ran into it through an open-jointed land drain. For some 
weeks before this was known the extraordinary vigour of several 
of the plants attracted notice. A little plant of Water Violet 
planted in the spring had become a square yard of stout vigorous 
branches, while three others planted at the same time in separate 
ponds had only made a few new shoots in the ordinary fashion. 
Calla palustris, Pontederia cordata, Villarsia nymphseoides, and 
others planted near the mouth of the pipe through which the 
escaped sewage entered the pond all showed such unwonted 
vigour as to extend far beyond the bounds assigned them, becom¬ 
ing crowded and somewhat unsightly ; for aquatics never look 
so well as when each plant or group stands out clearly from the 
others margined by clear water. At length the discoloration of 
the water and its foul odour showed the probable cause, and the 
sewage pipe was repaired. 
Although it was thus made clear that aquatics do like manure, 
it by no means follows that its use is desirable either in a solid or 
liquid form, excepting, perhaps, for the promotion of quick strong 
growth in a newly planted pond, or when it becomes desirable to 
increase stock quickly in a nursery garden ; for mere size in this 
class of plants does not constitute beauty, a coarse rank growth 
tending to rob many of them of the elegance and refinement of 
their normal condition. The Arrowheads and Callas are the 
probable exceptions, for it may safely be said of all of them that 
beauty grows with size. Certainly I have never seen the double 
Arrowhead so fine as it was this year both in foliage and flower. 
Twice have I lost the Water Violet from its being overgrown 
and killed by other plants, its growth without manure being very 
slow and so fragile as to be liable to destruction from a variety of 
causes. Now, however, I have enough in a single season to stock 
a dozen ponds, and intend to fill a little pool with it for future 
emergencies. 
Since writing the above I have read in Burbidge’s “ Cultivated 
Plants, their Propagation and Improvement,” that “ it does not 
appear to be generally known that manure has a wonderful effect 
on the common white Nymphsea alba, causing it to grow with 
tropical vigour, and produce leaves and flowers twice the ordinary 
size, and so distinct in appearance that one would readily imagine 
plants so stimulated to be a distinct variety.” This statement 
appears to me so important that it is worth quoting.—E dward 
Luckhukst. 
THE COLOURS OF FLOWERS. 
Decandolle’s opinion that “ blue and yellow being the two 
primitive colours of flowers, and always exclusive of each other, no 
blue flower ever changes to yellow nor yellow to blue,” certainly 
needs some modification to bring it into accordance with well- 
known facts, and, as “ C. M.” suggests at page 591, last volume, 
the subject is well worthy of consideration to determine upon 
what grounds that statement was founded. A few preliminary 
observations upon the origin of colours may, however, not be out 
of place. 
The rich tints of yellow and red assumed by leaves in autumn 
have been considered by many botanists, chemists, and others to 
be due to the varying oxidisation of the chlorophyll, which gives 
the colour to green leaves, and that similar changes are effected 
in this way has been proved by the fact that the sap of some 
plants is greatly altered in tint upon exposure to the air, such 
changes being, however, prevented when the cut portions of plants 
are at once plunged into a liquid or gas which does not contain 
any oxygen. Though the colouring matters of flowers differ in 
constitution from the ordinary green chlorophyll of leaves, yet the 
red or yellow substances in leaves have been found to be chemi¬ 
cally similar to Ike same tints in petals or bracts, and on that 
account they have been considered due to the same cause—namely, 
oxygenation. Upon these facts the classification of colours adopted 
by Decandolle was founded. This was originated by Schubler and 
Funk, who classed them in two series, the “ oxydised ” and the “ dis- 
oxydised,” termed by Decandolle respectively the xanthic (yellow) 
and cyanic (blue) series. These were arranged as follows, exclud¬ 
ing white as a negative condition and green as a combination of 
the two series. Xanthic : red, orange-red, orange, orange-yellow, 
yellow, yellow-green. Cyanic : greenish-blue, blue, violet-blue, 
violet-red, red. From the observations then made it was con¬ 
sidered that the range of variation in the flowers of a plant would 
be confined, with few exceptions, to one of these series, and how 
far that is the fact will be discussed further on. 
Different views have, however, been held regarding the cause of 
variation in colours. Thus it has been observed that the expressed 
juice of most red flowers is blue, and this is supposed to be due to 
the colouring matter being reddened by carbonic acid which 
escapes on exposure. “ The same blue-colouring matter as that of 
the Violet exists in many other flowers, and seems also to form 
the most usual red of the red flowers, in which it is apparently 
reddened by an acid, for many of these reds become blue when 
neutralised by an alkali, and green and yellow by an excess of 
alkali.”—( Brande Sf Taylor's “ Chemistry .”) The application of 
vegetable blues, such as litmus, as tests for acids, is well known ; 
acids cause the blues to become red, and alkalis restore the blue 
colour. Other investigators have concluded that there is only one 
colouring matter, which is termed chromogen, consisting of two 
principles, one forming a red compound with acids and the other 
a yellow with alkalis, the green being produced by an admixture 
of blue with the yellow. But one of the latest writers upon the 
subject, Mr. Sorby, notices the similarity in many instances of the 
colouring matters in flowers to those in leaves from which the 
chlorophyll has disappeared, and considers that such matters are 
already contained in the tissues of plants, and only require to be 
variously modified to produce all the tints which render flowers 
so attractive. He states, “ The facts seem to indicate that these 
various substances may be due to an alteration of the normal 
constituents of leaves. So far as I have been able to ascertain, 
their development seems as if related to extra oxidisation, modi¬ 
fied by light and other varying conditions not yet understood.” 
The two last theories seem to be partially in accord with that first 
mentioned, and it may be well to endeavour to ascertain how far 
they are borne out by facts. 
To form an idea of the range of variability of plants we cannot 
select any better fitted for the purpose than those which have been 
some time in cultivation, and which have been the special objects 
of horticulturists’ attention. In the improvement of those plants 
hybridising has had an important effect, and results have been 
obtained within the average life of a man that, judging by the 
extent of the divergence from original types and the comparatively 
slow manner in which such changes are effected in a natural state, 
would probably have taken centuries to produce without artificial 
selection and assistance. In races of plants that have been cul¬ 
tivated for hundreds of years we might expect an even greater 
range of colours than of other characters, and that is so; yet not¬ 
withstanding the prolonged careful efforts to extend the range of 
colours, it is surprising how closely they keep within certain 
lines, corresponding in some measure with the xanthic and cyanic 
series already mentioned. To exemplify this I have selected the 
following as amongst the best known kinds or races of plants that 
may be classified under five heads : 1, Those having varieties with 
yellow and blue self or parti-coloured flowers ; 2, Those with 
yellow or orange flowers, but excluding blue ; 3, Yellow or orange 
with purple ; 4, With blue flowers, but excluding yellow; and 
5, Purple, exclusive of yellow. In this way the plants will rank 
as follows :—1st, Pansies, Violas, Hyacinths, Crocuses, Iris ger- 
manica, Aquilegias, and Auriculas ; 2nd, Tulips, Azaleas, Carna¬ 
tions, Roses, Tuberous Begonias, Abutilons, Antirrhinums, Fuchsias, 
Helianthemums, Gladioli, Lantanas, Narcissuses, Rhododendrons 
(greenhouse hybrids), Chrysanthemums, Calceolarias, Bouvardias, 
and Potentillas ; 3rd, The first eleven yf the last series are also 
included in this, together with Primula vulgaris and acaulis and 
Picotees ; 4th, Canterbury Bells, Cinerarias, Achimenes, Clema¬ 
tises, Delphiniums, Gloxinias, and Verbenas ; 5th, Pentstemons, 
Petunias, Phloxes, Primula cortusoides, Rhododendrons (hardy), 
Pelargoniums, Primula sinensis, and Balsams. Thus, in forty-one 
examples we have only seven, including both blue and yellow, 
while there are seventeen possessing yellow, but excluding blue. 
It is curious, however, that eleven of the latter should possess 
purple tints, which may be considered as varying only in the pro¬ 
portion of blue they contain, red-purples being more common 
