FERTILISATION OF PLANTS

Otago Witness, Issue 2545, 24 December 1902, Page 10

FERTILISATION OF PLANTS

Although it docs not appear to pertain to practical gardening, eveiyone taking an interest in horticulture shou'd make it a duty to know as far as possible the secrets wrapt up in Nature's handiwork. These secretr are being unfolded by scientific- rV search, and although a dry disquisition thereon is not desirable in these^columns, a record of -plain faors as -*hey are -brought to light is interesting and should pi'ove acceptable Nature, in all her aspects, has f.omething alluring and fascinating, and no branch of study reveals greater wonders than that of botany. Great achievements have been accomplished, still the final has not I been jeaflked. The iexUliguut sujd prq£aga>

ing of plants is effected by many methods; natural and artificial, and with these we ' should make ourselves acquainted. In' a recant address Professor Henslow first described the process of fertilisation in Orchis Morio, exhibited by Mr Wallace, ' and another of Phaleonopsis grandiflora, calling ■attention to some fine blossoms of Cattleya labiata Warnerii, sent by Mr James Douglas 1 to demonstrate the fact that orchids do not degenerate if properly treated, for the plant from which they were gathered was a portion of one exhibited by Mr Rucker in 1866. A very interesting and instructive discussion had been going on at the society meetings on the "Variation, struggle for existence, and consequent survival of the fittest among plants," the main point being, "Does a hybrid reproduce itself true from seed?" On this' question dierse opinions were/ given by a large . numbers' of experts on. plants belonging to different orderar Mr Henslow. alluded to a • pajper by M. Noel Bernard, appearing in a ' magazine in 1800, upon the germination of orchids, /which had always been a matter of' greats difficulty. This arose from the vfacb that the seeds, which are always in <vi "arrested pro-embryonic" condition, will not germinate unless a particular microbe i 3 in the soil, which is required for a symbiotic -existence. Mr Bernard stated that little difficulty is met -with if the seeds of any " Vpecies^be sown >in%t-he >oil in which. -a- plant of ,t-hat. species. Has-been growing, -as it' i 3 ..impregnated "with ilie" ■ particular ' microbe required* ' '"'"'". . ' , ..j-HerV" we liavef another <v secret ' -extracted^ from/ the- large' rolur&e ~oix" the.. ~table,'<of • Nature ? inviting' inspection and reee'areb: No, one 'in *6he 'whole economy is' independent! of. the other; all are~tied to- j gether by cords, strong' and certain, 'though not- visible, regulated by. potent^ agencies as to increase or diminution. The old story of Clover, Bees," Mice, and Cats is very apt. The clover must be fertilised by bees, but mice destroy the combs of the bees, and if the cats are' too few in number to keep down the ,mice, bees cannot exist, and the clover cannot produce seed. Again, different plants require the aid of different insects; others are independent of" such assistance. The white and other clovers are otherwise fertilised ; the red alone requires the bee. Then, again, the honey-bee is of no use, the big bumble alone being adapted to the purpose. In another aspect the soil produces the plant, the plant secretes the honey, which the bee abstracts, and in turn fertilises tho flower, so as to reproduce its own likeness, and in the end all return to the earth from 'which they sprang. Some other plants have their method of communication still veiled in obscurity". The aeuba, to which notice was formerly given, is a noted example. The male plant may be at a considerable distance from the female, with masses of taller trees and plants intervening, obstructing or attracting insect- flight. How; then, is contact effected? The general theory is that the vitas principle " emitted . is borne in the - atmosphere, * and ! sexual attraction brings it to the desired ] spot ; and in support of this the instinct of animals and birds is quoted, and the long, distances they travel to mate— the wild, denizens, of woods, and prairies being 'cases in point. The opinion is held , : by many^ that there is an affinity, however > el&nder,' between animals and. vegetables. . , , Another class in the plaint world which,' .though jiot v very commo^niy 'cultivated -with., us, possesses some peculiarities "as to propa-,- . gation well' worthy of particular notice are „ . AQUATIC .PLApSTS. • The professor of botany in the City London College, in a recent paper, said that gardeners group plants primarily according to their requirements ,as to heat, protection from frost, and moisture. They can for the purposes of this grouping pay little heed to those structural characters which determine . the classification of the systematic botanist, j If we have «n orchid house, the gardener | cultivates in it only the more tropical, and 1 mostly epiphytic, niernbers of the order, not ' the terrestrial specimens of our chvn climate ; ! whilst on his rock garden he will assemble members of many different natural orders, natives of many widely distant mountains, omitting our own. He is, in short, primarily a practical physiologist rather than a student of botany. It is recorded that the number of flowering water plants is not large, and their geographical distribution, especially in an easterly and western direction, is far wider than is that of average land plants. Thu3, while most British speci&s of aquatics range throughout the north 'temperate zone, the watercress (Nasturtium officenalis), as is well known, has rapidly increased in the waters of New Zealand, and some of tho sub-tropical genu3 will' often- escape from indopr tanks, Land though susceptible to frost • spread for a time in exposed waters. .Almost ;.all aquatics' are * perennial, and in temperate waters, a period of hibernation is a necessity, and this as carried di.it in a variety of ways. Some sink to the bottom iv autumn and rise again in. spring : others form rhizomes in -the mud, and lie down in j them in autumn like land perennials ; j another- group,- a large species, form special winter buds with -closely-packed leaves, which drop off and sink to the bottom, and spring again in due season. Again, the duck-needs form numerous ir-inute branches, which become detached ; the .mother plant sinks, and the offsets start as new plants. The hornwort dies away behind and grows in front, and the branches become separate j plants. The American waterweed by this process has, during the last 60 years, spread over almost all the inland waters of Western Europe, seriously affecting navigation. 1 "Water offers a serious obstruction to light, so the sea is almost destitute of green plants, and at moderate depths the algse present the appearance of growing in the shade. How water act 3in the increase of plants inhabiting it is a difficult problem. In the water starwort the submerged leaves are" longer and narrower the ieeper they aro from the surface ; in the case of the jnare's tail, whilst the aerial leaves are only eight or nine times longer than the breadth, the submerged once are in length 30 times their width. Several aquatics, are rooted in the ground, and no doubt receive a large 3 mount of sustenance from the soil, but whether rooted or floating, all of them -re- j ceive the greater part of their food from the water,- which contains a large amount of j gases. Decomposition produces onhnonia, which is easily soluble, and is a valuable requisite for vegetable life. The .researches of the scientist are of , immense value, to the gardener, opening up to him secrets iv natuz-e deeply affecting hi 3 trade, and which could not be lkeovered in practical operation, and as every ilass of plant has its own peculiarities a full knowledge thereof is most. de=i r »ble, which gives not only a ze&t to, but secures success in, the cultivation. The ferns, lycopods, mosses,

brackish,' and marine algae, open an' im-' mense field for observation. Hooker says'' of the algae that there 'being so many- genera whose .position is doubtful in sub-orders — obviously 'modifications of one 'common plan — they-may with propriety beregarded as-a naturaP order equivalent to such others as the. grasses)' lichens, fungi," eto. Though so different in habit, locality, and general appearance from lichens, the .absolute- difference between: these 'orders is, in some' instances, reduced to .very small -proportions. Wjth fungi also their affinity is very close, and finally some of the present appearances in certain stages of development render -it impossible to say whether they should be referred to as belonging to^-the. animal or the -vegetable kingdom. Marine algae occur at all depths. '-in. , the ocean between' high tide or its spray 1 , and upwards of 100 fathoms deep ; but they abound mostly between tidal , limits,, or just beyond s them. As a rule- the . bright green kinds occur nearest to high-water- mark, and extend to fresh water ; the dark olive-green occur between- tidal, marks; and the bright red affect deeper water ; ..but to this there are ,many' exception?. > The great sea- weed that forms olive-green floating "patches girding New Zealand harbour3,.Hoofcer had seea off the Crozet Islands /at 40 fathoms sounding, and he had reason to suppose they -were 700 ft long. \ v ■ Now Zealand .13 "very -rich "in algae.-. Its, deep waters, quiet., soundsl especially abound --in', specie*'.. oi_ this,, interesting - "and « 'beautiful' order, wliicji. DjvLyall. .'has .admit-"-.ably '* eo!l^eteas ,as Miss " Lancisbof ougk, has , Bone. for thefee' ou v the,. British eoastr, -thusaddressing, them r^- .- -,»{ : / ; '' - v * Gall us "riot'~ weeds; ' W© are flowers 'of" the sea. A large number- of , enthusiasts have been engaged in classifying., and arranging our 'algae, and, although the list is a large one, it is still incomplete, and further diligent research may reveal others, unnoticed. The pursuit will afford pleasant .occupation for a holiday- at the coast. j , I. M. I j

Thirteen, pears, weighing- 501b 3ioz together, were recently picked at Jersey One of the objects of ,the Government, biologist's visit to the Cook group is to ascertain the desirableness of establishing State nurseries at the Islands. In the King's gardens at Frogmorc the asparagus beds have an aggregate- length of a mile and a-quarter. The rows of peas sown during the year would extend to about five miles if placed end to send. ' The length of the walls upon which, fruit trees . are j grown is over two miles;' pears occupy 1235 yds, plums 985 yds, cherries 840 yds, and apricots, peacheo, and nectarines the remainder of the syace. Many thousands of strawberry plants % are. annually potted up forgrowing under glass. .