Pale Flowers Research Articles

The Genetics of Evening Primroses and Mice

IN 1905, Dr. G. H. Shull, of Princeton, received from Dr. de Vries ten rosettes of Oenothera lamarckiana from the locality at Hilvershum, Holland, which had supplied the original material for the classic researches of de Vries many years before. In 1921, among the descendants of these plants appeared a colour-mutation which Shull calls old gold (vetaurea). The petals are flushed with apricot-colour, strong toward the base, fading out distally. In a very interesting and detailed paper (Genetics, May 1926, p. 201), Shull describes the behaviour of this mutant in a variety of crosses. It is recessive to the ordinary yellow flower. In order to test it further, Shull introduced into his cultures the very pale yellow mutant called ‘sulphur’ (sulphurea), and was surprised to find that-old-gold was complementary to sulphur, the two when crossed giving invariably plants with flowers of the normal yellow colour. Accordingly the normal yellow is expressed by the symbol SSVV (double dominant), the homozygous sulphur by ssVV, and the homozygous old-gold by SSvv. By suitable crosses the double recessive ssvv was obtained, and proved to be a pale flower, with the bases of the petals flushed with the apricot tint. Shull called it gold-centre (aurata). The amount of the reddish or old-gold colour is much less than in old gold.

DESCRIPTION OF THE LARVA AND PUPA OF AULAX NABALI

The tall White Lettuce, Nabalus altissimus, Hooker, is a striking and graceful plant. At Quebec it is found in glades and on the edges of woodland roads. Its wand-like stems rise sometimes to the height of six feet, and end in panicles of greenish-white or pale straw-coloured flowers. The stems are hollow, but have a lining or inner coat of white downy pith, which in the summer is sometimes found to be broken with discoloured warts. Late in the fall, when the stems of the plant have become indurated and the pith has dried up, the warts are found to have developed into galls of the size, shape and colour of grains of hemp. I have found them in the stems from about six inches above the ground up to a height of three feet or perhaps more. Sometimes they appear in clusters, sometimes in rows, and sometimes singly at intervals. The proper inhabitant of each of these galls is a footless, spindle-shaped grub, one-eighth of an inch long. In colour it is like white wax, with the mouth organs brown. It is more pointed at the head than at the other extremity. It lies curled round in the gall.

Alteration in the Colours of Flowers by Cyanide Fumes

IT is well known that the yellows of some insects are turned to red by the fumes from potassium cyanide; but I have not, after some inquiry, been able to obtain any literature describing the effects of such fumes upon the colours of flowers. The reactions I have observed are very curious, and while it seems improbable that they are hitherto wholly unknown, it may not be amiss to direct attention to them. A few lumps of the cyanide are placed in a corked tube, covered with a little cotton, and the flowers are placed on the cotton. It is probably necessary that the day should be hot, or the tube slightly warmed. The pink flowers of Cleome integrifolia and Monarda fistulosa turn to a brilliant green-blue, and finally become pale yellow. A purple-red Verbena becomes bright blue, then pale yellow. The purple flowers of Solanum slaeagnifolium go green-blue and then yellow. The white petals of Argemone platyceras turn yellow—the natural colour of A. mexicana. The pale yellowish flowers of Mentzelia nuda turn a deeper yellow. Flowers of Lupinus argenteus, var., turn pale yellow. White elder (Sambucus) flowers turn yellow. The scarlet flowers of Sphaeralcea angustifolia turn pale dull pink, resembling somewhat a natural variety of the same. Any of your readers will doubtless obtain similar results with the flowers growing in their vicinity.

Letters to Editor

ALLOW me shortly to resume the different views which have been proposed in your columns, as giving a possible explanation of the fact that the flowers of F. pallidiflora attain their brightest colouring when the time for fertilisation has passed, and to point out the observations indispensable to be made, in order to ascertain which of the proposed views is right. 1. It is possible that nocturnal Lepidoptera are the fertilisers of the fumitory; in this case it would be most probable that the pale colour of its flowers has been acquired by natural selection, pale flowers being most conspicuous in the dusk. 2. Diurnal insects may be the fertilisers, and the pale hue may be sufficiently conspicuous or even more attractive for them than the brighter one. In this case, also, the former must be considered as acquired by natural selection; the latter, on the contrary, as in the first case, merely as the result of chemical processes. 3. Under the same supposition of diurnal insects being the fertilisers, it is possible that the older flowers, by their brighter hue, serve to attract insects to the younger and paler ones; in this case the bright hue of the older flowers may be looked upon as acquired under the influence of natural selection, the pale colour of the younger flowers at the same time being useless. 4. It is possible that self-fertilisation is the rule with the flowers of this fumitory, and that cross-fertilisation by insects takes place only very exceptionally; in this case not only, as in No. 3, the paler colour, but also the brighter one would be nearly independent of the influence of natural selection. In order to decide definitely which of these views is right, it is indispensable to watch perseveringly the flower of this plant, and to ascertain what kind of fertilisation naturally takes place. In case diurnal insects should prove by direct observation to be the fertilisers, it would be possible to decide whether supposition 2 or 3 is correct, by removing from many specimens every older flower as soon as its colour, begins to grow brighter, and by observing whether these specimens or those with older and brighter flowers are more frequently visited by insects.