CROSSING CHRYSANTHEMUMS

Star (Christchurch), Issue 9254, 5 June 1908, Page 3

CROSSING CHRYSANTHEMUMS

« In making crosses of chrysanthemums (writes the English " Gfardener's Chronicle "), care should be taken to select those varieties for parents which pos cess desired characters. Crossing by no means implies a blending of qualities; often it is simpler, and results iv the transmission of a single quality. The chrysanthemum is a composite, and, in the case of what is termed the flowered type, each flower-head is composed of two distinct sets of florets — the inner or disc florets and the outer or ray florets. The/ray florets give the characteristic colour to the flower-head, whereas the disc florets are almost invariably of a bright yellow colour; the new variety Phyllis has a white centre, and is therefore a notable exception. According to the National Chrysanthemum Society's rules, the ray florets of the true single are restricted to three rows, if more rows are present they are termed "decorative singles." The disc florets possess both stamens and pistil ; they are therefore hermaphrodite, whereas the ray florets are female only. It follows that, in order to effect cross fertilisation, the disc florets with their anthers must be removed, leaving the ray florets, which are purely female. Tho first thing to do in making crosses is to select the parents j this, of course, needs practice, and the specialist who is best acquainted with the constitution and good points of the available varieties is the man most likely to be rewarded with good results. Those flower-heads which. are to be the seedboarers should be selected early, before th pollen from the disc florets is ripe, thereby preventing 6elf-pollination ; at the same time, the entire disc or cent* must be removed, leaving only the ra\ florets. Having taken this precaution the ray florets should be covered over with a muslin bag until such time as the stigmas are ready for pollination. The stage at which the florets are ready for pollination is reached when the flowers are fully developed; the pistil is then divided into two at its apex, thus exposing the receptive stigma. Pollen may now be applied from the mature flowers of the selected male plant. A bright day should bo selected when the pollen in dry and dustlike. Experience teaches one to use plenty of pollen. In the caee of the chrysanthemum, pollen may be satisfactorily conveyed by means of a camel's hair brush, which is soft and not liable to bruise the stigmas. At the same time, it is not ahyays to be recommended, particularly if one is short of pollen, since much of it is lost among tho hairs of the brush, and, besides this, there is always a risk of stray pollen being left behind after efforts to cleanse the brush. A clean knife-blade, a pencil, or the operator's thumb-nail are excellently adapted for securing artificial pollination. After pollination, the flower-heade should again be covered up, and the plants left in a suitable place to allow fertilisation and the ripening of seeds to take place. It is always advisable . to take reciprocal crosses, for neither parent has the particular character of transmitting a special quality to the offspring. Experiments prove that the male parent no more exclusively imparts colour to the cross than does the female, and the same applies to other characters. After making crosses each one should be labelled and a record kept for reference.