ROCK GARDENING

Hutt News, Volume 1, Issue 32, 17 January 1929, Page 3

ROCK GARDENING

(Continued fxoiu Page 2)

for the fertilisation of their flowers, retain the power of setting seed as a result of self-pollination, should cross-fertilisa-tion not be achieved. The special means by which this is arranged are very vari-^ ed and a few of interest, as they affect some of the more popular of rock-garden subjects, may be briefly .described. One of the most generally admired of all Alpine species is the so-called Stemless Gentian or Gentianella, whose bold, funnel-shaped flowers of intense blue rise in patches of thousands from the grassy slopes or rock ledges in the Alps, forming sheets of indescribable brilliance. ' In wet weather, when insects are scarce, the blossoms close up and droop toward the ground and when such weather condi: tions prevail, as is not infrequently the case, for several weeks, all chance of cross-fertilisation is lost. ■

Nevertheless, seeds are almost invariably developed from the flowers. If one of the blooms of a Gentianella is cut in half from top to bottom, it will be found that the arrangement of the stamens is peculiar the filments, instead of being free throughout their length, •have their basal halves joined to the lower portions of the inside of the corolla, so that they appear as ridges which join the column-like ovary, dividing the corolla tube into five cylindrical passages. The anthers are borde about half-way up the funnel of the corolla and, immediately as the flower opens, are covered -with pollen. The" stigma is lobed and projects beyond the level of the anthers at the top of the flower and so long as the blossom is upright cannot, therefore, be dusted by pollen from its own flower. If the male dust is not carried away by visiting insects, it is shed by the anthers and falls into the passages already mentioned, where it accumulates at the bottom of the tubes. v As the bloom droops in bad weather, this dust naturally falls from the base of the flower —which now occupies a higher position than the mouth —and comes into contact with the stigma thus ensuring the fertilisation of the ovules, The Pasque Flower (Anemone Pulsatilla) is another rock-garden favourite which has an interesting method of guarding itself against lack of insects during the flowering period. When first ' ■ . ■ ■ ■ ■■■■'.••■

opened, the beautiful mauve blossoms are carried erect on short stalks and the anthers, held aloft on rigid filaments, form a densely packed mass around the numerous stigmas. 'Some forty-eight hours after opening, the flower stalk elongates and the inner series of anthers discharge their pollen, which may be collected by insects or fall on to the inner surface of the cupped and coloured sepals. At night, the flower closes and hangs its head, so that pollen adhering to the sepals is brough/t into contact with the stigmas, about which they close. The flower stalks, continue to lengthen. and in another two days the blossoms droop by day as well as by night. By this time all the stamens have lost their rigidity, their anthers are open and the pollen is shed into the flower cup. The sepals have also- lengthened somewhat, with the result that the pollen lying on their inner surface is brought to the same level as, and in contact with, the stigma. .- .' '