November 39, 1907 



HORTICULTURE 



704 



Floral Colors 



Primitive Colors. 



The various colors of flowers are not, 

 as might be supposed, the result of 

 chance, for their existence and further 

 production appear to be the result of, 

 and to follow, certain laws. 



There still appears to be some dif- 

 ference of opinion as to what was the 

 primitive color of flowers, supposing 

 that there was only one color in the 

 first flowers. Some maintain that the 

 first color was green, others that it 

 was yellow. There is, however, little 

 doubt that primitive vegetation being 

 compos3d of flowerless plants was en- 

 tirely green, the coloring matter of 

 which was, as it is today, chlorophyll. 

 This chlorophyllic green is divisible 

 Into two other colors, a strongly yel- 

 lowish green and a distinctly bluish 

 green. To these two pigments the 

 names of Xanthophyll and Cyanophyll 

 have been given, and are generally 

 considered the primary sources of all 

 the various colors exhibited by flowers 

 today, and which may be divided into 

 two classes in the order of their ap- 

 pearance in time: — 

 Green 

 I 



Cyanthic, 



Blue-green 



Blue 



Blue-violet 



Violet 



Violet-red 



Xanthic, 



Yellow-green 



Yellow 



Yellow-orange 



Orange 



Orange-red 



\ 

 Eed 



Flowers are therefore Cyanthic — that 

 is, capable of varying from blue to red 

 and white, but never yellow or orange; 

 or they may be Xanthic, being able to 

 vary from yellow to red and white, but 

 never blue or violet. This seems to 

 point to the futility of expecting to 

 produce a blue tulip, rose or dahlia; 

 nor, on the other hand, is it likely 

 that we shall ever see a yellow gera- 

 nium. 



Some botanists, however, consider 

 that white was the primary color 

 (leaving out green, as in botany green 

 is not, strictly speaking, a color), but 

 there appears to be little evidence to 

 warrant such a conclusion, at least so 

 far as plants are concerned, although 

 in this connection we must not forget 

 that the combination of all the colors 

 of the tpectruni produces white. 



That variation in flower-color fol- 

 lows one of the above series is, I 

 think, obvious not only by what has 

 been produced in the way of color by 

 artificial selection and hybridisation, 

 but also — and more so — by what has 

 not been accomplished. 



Vegetable Pigments. 



Apart from its origin and relation to 

 flowers, color is a subject which is a 

 large and difficult one, comprising as 

 it does its physical, physiological, 

 chemical, and biological sides. The 

 chemistry of the vegetable pigments is 

 especially difficult, and is confronted 

 with the initial difiiculty of isolating 

 •most of them from otiier plant-prod- 

 ucts so that they may be obtained in 

 a state of purity. The biological site 

 is chiefly connected with the question 

 of the inheritance of pigment and the 

 losses and gains of pigment in individ- 

 ual plants which constitute color-va- 

 riation; and it is here that great con- 



fusion exists, for both Mendelists and 

 anti-Mendelists concern themselves 

 very little about the inheritance of pig- 

 ment, but much about the inheritance 

 of color, which is quite another mat- 

 ter. 



'Breeding for Color. 



All those who have been engaged in 

 hybridising plants, and especially in 

 producing new color varieties, know 

 full well the difficulties and uncertain- 

 ties which are attached to attempts to 

 breed varieties pure from seed. In 

 spite of present uncertainties, more 

 evidence is being obtained year by year 

 which points to the fact that whatever 

 the color which may be produced it is 

 the result of fixed law. known as the 

 law of heredity, and which is based up- 

 on the theory of the continuity of the 

 germ-plasm. At present this law is 

 incapable of being demonstrated in 

 terms on similar lines to that of a 

 chemical formula, that is to say, that 

 point has not yet been reached when 

 by the crossing of two varieties of 

 plants, whether of the same or of dif- 

 ferent colors, we can be sure of the 

 color or colors which will be exhibited 

 by the offspring. 



At tlve International Conference on 

 Plant Breeding in 1902, Professor Wil- 

 liam Bateson, M. A., of the University 

 of Cambridge, England, stated, "We 

 have now a clear notion of the mean- 

 ing of purity or fixity of type and of 

 the consequences of dominance — phe- 

 nomena which go to make up the 

 daily experience of those who are 

 practically engaged in plant-breeding. 

 Apart from the profounder mysteries, 

 the unravelling of the problems of 

 heredity has now become a matter for 

 statistical research, and we may con- 

 fidently look forward to the time when 

 the laws of heredity will, in their out- 

 ward presentations at least, be as the 

 laws of chemistry now are, a matter 

 of everyday knowledge." 



An Interesting Lecture. 



Professor Bateson is now in this 

 country, and on October 30th, last gave 

 an extremely interesting lecture on 

 The Inheritance of Color in Animals 

 and Plants, which may be taken as 

 embodying as far as it went the latest 

 discoveries on Mendelian lines of the 

 laws connected with the subject. The 

 lecture was naturally of a technical 

 character, but, being copiously illus- 

 trated by diagrams and lantern slides 

 the latter splendidly reproduced from 

 photographs, was easily followed by a 

 large audience. Practically the lec- 

 ture was confined to plants, and the 

 photographs from which the slides 

 had been produced were taken, with 

 one or two exceptions, from plants 

 grown by Professor Bateson himself. 

 Mendel's Discoveries. 



He commenced by stating that "The 

 discoveries of Mendel in the middle of 

 the 19th century, when applied to 

 biology in general, prove the inheri- 

 tance of color to be the most com- 

 plicated of transmitted characters. 

 Mendel discovered that plants are not 

 sin^.ply plants with a'l their diverse 

 attributes, but that they are composed 

 of elementary factors, which when 

 combined make up their different com- 

 plicated characters; and also that 

 when the genu cells are formed those 

 comiilications are analyzed, as it were, 

 by the germ-cells so that the elements 

 are dividi^d among those germ-cells. 



Further, that the germ-cells due to the 

 different parent-plants remain sep- 

 arate, and each germ-cell from each 

 parent produced similar cells and no 

 others, in equal numbers. The truth 

 of this rule has received striking con- 

 firmation by the discoveries of Mr. 

 Hearst in England when applied to the 

 color of the eyes in man. Blue eyes 

 have the coloring pigment at the back 

 only of the iris; but brown, hazel, or 

 grey have pigment in front as well as 

 bdi'ind. llierefoie the human eya 

 can as regards color be divided into 

 tv.o classes, those having coloring i)ig- 

 ment behind only and those having it 

 both behind and in front of the iris. 

 It is considered that those iiaving no 

 pigment in front are recessive. Broad- 

 ly speaking, parents with no pigment 

 in front will have children like them." 



Experiments with Sweet Peas. 



The lecturer then illustrated some 

 experiments with sweet peas. A tall 

 one five feet high had been crossed 

 with a dwarf of only nine inches in 

 height; the resulting progeny were all 

 tall. These tall ones produced in the 

 next generation three of tall to one 

 of short, and, he said, "ii these latter 

 are kept pure the tall will alwajs pro- 

 duce tall, and the short will always 

 produce short." 



"Albinoism." the Professor said, "is 

 recessive, but albinos on being crossed 

 with colored always gave colored off- 

 spring, but if when these colored off- 

 spring bred, white ones were pro- 

 duced, these latter if kept pure would 

 breed white indefinitely." The re- 

 sults of a very striking experiment il- 

 lustrating tills point were then shown. 

 Two white sweet peas were crossed, 

 and the result was a purple identical 

 in character with the wild sweet pea 

 of Sicily from which all our garden 

 sweet peas originated. "This" said 

 Professor Bateson. "proves that in one 

 or both of the whites some of the 

 germ-cells of the original wild type 

 continued to exist. On carrying this 

 experiment further I found that breed- 

 ing from the resulting purple produced 

 nine of all colors, purples and reds, to 

 ^.•^ven of white. 



Some Facts for the Hybridist. 



"Thus you cannot tell the composi- 

 tion of a plant by merely looking at it, 

 and experiments on Mendelian lines 

 prove that the surest method of analy- 

 sis was to conduct a series of breeding 

 experiments, and by this means anyone 

 thinking of hybridising with a view of 

 producing a plant of a special color, 

 should first find out the composition 

 of the color or colors of the proposed 

 parents because, as shown, two or 

 more white sweet peas may have each 

 a different color composition, and the 

 same applies to all colors. In the 

 course of my experiments with sweet 

 peas I have frequently had purely, fe- 

 male plants which, as they pro- 

 duced no seed-pods, were continuous 

 bloomer.s." 



Illustrations of breeding from a 

 white Primula Chinensis showed prac- 

 tically the same results as those of the 

 sweet peas. 



An instance of natural hybridisation 

 was described and illustrated. A hy- 

 brid viola was discovered which was 

 undoubtedly the result of a cross be- 

 tween a species with a papilionaceous . 

 leaf and one wit,h a pedate leaf. The 

 seeds of this hybrid were sown and 



