. Botany for agricultural students . Botany. THE TWO GENERATIONS 411. foot extends into the gametophore and absorbs food which is supplied to the elongating stalk and developing sporangium. In the sporangium are produced numerous spores and also elongated twisted cells called elaters, which assist in scattering the spores. When the spores are mature the sporangial wall opens and the spores are scattered. When the spores fall on a moist substra- tum, they germinate and produce new thallus plants like the ones described. The Two Generations. — The ob- long body produced by the fertilized egg, an
. Botany for agricultural students . Botany. THE TWO GENERATIONS 411. foot extends into the gametophore and absorbs food which is supplied to the elongating stalk and developing sporangium. In the sporangium are produced numerous spores and also elongated twisted cells called elaters, which assist in scattering the spores. When the spores are mature the sporangial wall opens and the spores are scattered. When the spores fall on a moist substra- tum, they germinate and produce new thallus plants like the ones described. The Two Generations. — The ob- long body produced by the fertilized egg, and consisting of foot, stalk, and sporangium, is regarded as a plant within itself. When fully mature it is so small that one must look closely under the finger-like lobes to find it. It doesn't look much like a plant, since it is so simple and depends upon the gametophore for food and water, but it is this plant that differenti- ates and becomes the conspicuous plant body of the higher plants. Since it produces spores, it is called a spore plant or sporophyte. When one is reminded that a Corn plant or Apple tree is all sporophyte excepting some microscopical structures within the flowers, then the significance of this small sporophyte of the Liverworts in relation to the origin of the higher plants may be realized. It is obvious that if this little sporophyte is regarded as a plant, then all of the remainder of Marchantia must be regarded as another plant. This other plant consists of all that has been described as the plant body of Marchantia. It consists of the flat prostrate thallus and the gametophores with the sex organs and gametes. Since it is the function of this plant to bear gametes, it is called gametophyte. It follows then that the complete life cycle of Marchantia in- volves two plants or generations as illustrated in Figure 367. The gametophyte generation develops from a spore and produces Fig. 366.— Highly magnified vertical section through the expanded top o
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
