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blown in from neighboring fields and roadsides. Cultivation will readily destroy the weed and where it is abundant in fields shallow cultivation, followed by the disk and harrow, should be effective. Mustard.—The first and most important consideration in connection with the extermination of mustard is that the oats or wheat should be freed from mustard seed. Then this grain should be sown on clean fields, preferably fields that have been in pasture or meadow. Nothing has done so much to remove the weeds from the fields of northwestern Iowa as the pasture and meadow. If the grain is sown in a corn field there should have been no mustard the previous season. Having sown the small grain on a clean field, there is always a chance that some of the seeds will retain their vitality in the soil. If much of this mustard should come up it may become necessary to spray it with iron sulphate. Where the mustard is abundant this is a very effective means of destroying the weeds, using the sulphate at the rate of one hundred pounds to a barrel of water. Indian Mallow or Butter Print.—Much complaint has come to us about Indian mallow or butter print. This weed, which is very common in many parts of the country, is of course readily destroyed by cultivation. The only trouble is that so much of the seed retains its vitality for a considerable length of time, how long has not been definitely determined. The best treatment for this plant is to get the field into meadow or pasture, leaving it in this condition for a number of years and then planting to corn and following the usual rotation. Morning Glory.—The morning glory, though a troubleSome weed in many parts of the North, does not seem to be quite as pernicious in its character as quack grass. In response to the queries sent out it is found that the best treatment that can be given the morning glory is to turn it into pasture. Cattle, sheep and hogs are very effective in keeping this weed down. One writer states that by keeping it in pasture four or five years the weed is killed. Mr. Cox, in addition to cultural methods, recommends the use of alfalfa as a weed exterminator. The plowing should be thorough and done as soon as the grain is removed in July or August, but it need not be deep, as the roots extend several feet into the soil and cannot be reached by plowing. Where

Fig. 34A. Wild morning glory or bindweed (Convolvulus sepium). (Photograph, Charlotte M. King.)

the weed is common the plowing should be followed by disking and harrowing and the roots should be exposed to the sun. One correspondent recommends corn, oats, and pasture. Another recommends millet, sorghum, and buckwheat as effective in the destruction of the weed. When a cornfield contains a considerable amount of the 1. orning glory the cultivation must be frequent and the hoe should follow the cultivation, especially to destroy the plants which make their appearance around the hills.

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CHAP'TER XIII.

THE MORPHOLOGY OF WEEDS The Root.—In the higher plants we are usually able to make out three conspicuous organs, namely: The root, stem and leaf, and at certain stages of development, a fourth organ, the flower. The root, stem and leaf have to do with the nutrition of the plant and the flower with its reproduction. In our study of a type plant, let us begin with the root. Roots naturally occur in the ground; they fix the plant in the soil and absorb water that holds in solution certain mineral constituents. The root increases - - in length from a point just back co, Fibrous root of of the tip, growth taking place at - this point. The tip of the root is called the root-cap and is continually wearing away, while new cells are as constantly being added from the growing point. Not far from the tip also are the root hairs, which absorb moisture from the soil. These become covered with particles of sand, because the cell walls are mucilaginous. There are four types of roots, classified according to duration: Annual, winter annual, biennial and perennial. In plants with annual roots, the seeds germinate, the plants produce flowers ...Fig. 3% Root g; . . showing root cap. and seeds the same season and then die. (...)

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The following are illustrations of this type: Awned brome grass, black medick, bracted plantain, brome grass, bur clover, buffalo bur, cheeses, chess, cockle, cocklebur, common sunflower, cowherb, dooryard knotweed, dog fennel, fetid marigold, Fuller's teasel, goosefoot, great ragweed, green foxtail, hairy brome grass, hedge mustard, horseweed, Jimson weed, marsh elder, Mexican fireweed, mustard, pepper grass, pigeon grass, pigweed, prairie bitterweed, prickly lettuce, purslane, Rocky Mountain bee plant, Russian thistle, small ragweed, smartweed, squirrel-tail grass, tumbling mustard, velvet weed, vetch, wild barley, wild oats. The seeds of winter annuals germinate in the fall, the plants live through the winter and in the spring produce flowers and seeds; shepherd's purse, speedwell, winter rye and winter wheat are types of this class. Such plants are more common southward than in the North. Plants which in the North are annuals may become winter annuals in the South. The seeds of biennials germinate in the spring, producing a growth of short stems and leaves the first season, but Fig. 37. Root hair. no flowers; in the second season the (Leavitt.) stem elongates, produces flowers and seeds. The following weeds are biennial: Bull thistle, burdock, mullein, Nelson's thistle, parsnip, and sweet clover. Other representatives: Cultivated beet, cabbage, carrot, and parsnip. Perennial plants produce roots which continue to live year after year. All of our trees and shrubs and the following weeds are perennial: Blue lettuce, buckhorn or ribgrass, Canada thistle, common nettle, common plantain, cowbane, curled and smooth dock, dandelion, dogbane, gaura, germander, horse nettle, ironweed, milkweed, morning glory, nimble will, northern nut grass, quack grass, tanweed, western nettle, wild liquorice, wild poppy, wild timothy, woolly thistle, yarrow. Other kinds of roots are the aerial, which are produced in the air, an example of this class being the roots of the poison ivy, the brace roots of Indian corn, trumpet creeper, etc. The brace roots of corn become absorbing organs as soon as they strike the ground. In the poison ivy, they assist the plant in climbing, taking the place of tendrils. In one class, including certain orchids, the plants become attached to other plants, but do not take any nourishment from them. These are known as epiphytes. In a third class, the roots are not only attached to other plants, but obtain nourishment from them. These are called parasitic plants, in which group are the clover dodder and green parasites such as mistletoe. Some roots become greatly thickened, such as in the sweet potato, • dahlia, carrot and turnip, the upo; per part of the turnip, however, gonum Convolvulus). being really a stem. Roots of this class store food for future use, and are known as fleshy roots. They are conical, as in the carrot; fusiform, as in the dahlia; turnip-shaped, or napiform when like those of the turnip. The Stem.—The stem occurs in an abbreviated form in the seed; but as we ordinarily see it, it is above the ground. It is spoken of as the ascending axis, and is divided into nodes and internodes, the leaves making their appearance at the nodes. In addition to the stems

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