. Botany for high schools. Botany. lO GROWTH AND WORK OF PLANTS (see fig. 16). They are really adventitious roots since they arise from the stem. The true lateral roots arise from the primary root and extend in a nearly horizontal direction, and the branch- ing of these finally results in a great mass of fibrous roots radiat- ing in all directions in the upper soil layers. About the same time or very soon after the root emerges, the conical fold of the leaves emerges from the other end of the groove. This conical form of the folded leaves wedges its way directly upward through the soil. The le
. Botany for high schools. Botany. lO GROWTH AND WORK OF PLANTS (see fig. 16). They are really adventitious roots since they arise from the stem. The true lateral roots arise from the primary root and extend in a nearly horizontal direction, and the branch- ing of these finally results in a great mass of fibrous roots radiat- ing in all directions in the upper soil layers. About the same time or very soon after the root emerges, the conical fold of the leaves emerges from the other end of the groove. This conical form of the folded leaves wedges its way directly upward through the soil. The leaves elongate and unfold. THE PINE. 13. The pine seed.—The seeds of the pine are formed on the upper (inner) surface of the scales of the pine cone (see paragraph 529 on cones of the pine). The seeds are oval and somewhat compressed and flattened, ^sc and attached to the lower end of the scale, two ,/f on each scale. As they become freed from the scale a long, thin and broad strip of the scale ^"^ splits off and remains attached to the seed as a wing. A section of the seed shows the thin Pine seed, section P^P^ry remnant of the nucellus lying between the of. sc. seed coat; «, g^g^j coats and the white mass of the endosperm. remains of nucellus; ^ end. endosperm (= Within this Hcs the cmbryo. The root and stem female gametophyte); embryo = young together form a sporophyte. Seed coat ^ and nucellus = re- straight cylindri- mams of old sporo- o •> P^yt^- cal portion, and at the stem end there is a crown of small needlelike leaves, the seed leaves or cotyledons. The cotyle- dons are numerous in the pines. The embryo is entirely destitute of chlorophyll, but during germina- tion, even if the seedlings are grown rwTng severS Toufr in the dark the leaves become green. In germination the radicle emerges from the micropylar end of the seed. The hypocotyl elongates and forms a loop which pulls the leafy end of the stem and the cotyledons from the Please note
Size: 1105px × 2262px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
