CHE REFERENCE LIBRARY - ZetaTalk

SEEDS AND SHOOTS 3or accident before the plantlet can escape. Other kinds havea more or less definite period of dormancy, within which timethey will not germinate even though conditions are favorable.Seeds of many of the wild herbaceous perennials will notgerminate till the following spring. Other seeds lie in theground two or three years before germination. On the otherhand, the seeds of some species germinate at once on maturity,even while on the parent plant as in the case of the mangrove.Special soils or other media, as to acidity, alkalinity or otherqualities, may be necessary for germination and growth, orpil~tic~lll:~r tl’WtI1l~Ilt, as etherization, may yield new results ;arldi it1 sww plants, as the orchids, it is now supposed thatcertain fungi are necessary to germination.Thus far, the knowledge of conditions and aptitudes is chieflyempirical, mostly the result of repeated and repeated trials,with their failures and successes. We must always learn theserequisite conditions by experience ; yet we are gradually discoveringa rational basis for our operations, and we may expectmarked progress it1 this direction in the years to come, renderingthe propagatiot~ of plants more definite and predictable.‘I’1115 PHYTONIt is not alone by seeds that plants multiply themselves.Many kinds rarely produce good seeds, and some of the cultivatedspecies are multiplied practically exclusively by the nonsexualand vegetatii.e parts. Familiar examples are the sweetpotato, horse-radish, sugar-cane in the United States, banana.Some species seem to be losing the power to produce seeds withthe enormous artificial development of other parts, as the Irishpotato.We may liken a plant to a colony of potential individuals,one individual being perhaps a node and a leaf, one growingon arMher and the aggregation making up a complex organism.