Elementary botany . m, we shall seethat one end of the seedcoat is caught againsta heel, or p e g,which has grown outfrom the stem for thispurpose. Now if weexamine one which isa littlemore ad-vanced,we shall see this heelmore distinctly, andalso that the stem isarching out away fromthe seed coats. As thestem arches up its backin this way it pries withthe cotyledons againstthe upper seed coat,but the lower seed coatis caught against this heel, and the two are pulled graduallyapart. In this way the embryo plant pulls itself out from be-tween the seed coats. In the case of seeds which are plante
Elementary botany . m, we shall seethat one end of the seedcoat is caught againsta heel, or p e g,which has grown outfrom the stem for thispurpose. Now if weexamine one which isa littlemore ad-vanced,we shall see this heelmore distinctly, andalso that the stem isarching out away fromthe seed coats. As thestem arches up its backin this way it pries withthe cotyledons againstthe upper seed coat,but the lower seed coatis caught against this heel, and the two are pulled graduallyapart. In this way the embryo plant pulls itself out from be-tween the seed coats. In the case of seeds which are planteddeeply in the soil we do not see this contrivance unless we digdown into the earth. The stem of the seedling arches throughthe soil, pulling the cotyledons up at one end. Then itstraightens up, the green cotyledons part, and open out theirinner faces to the sunlight, as shown in fig. 90. If we dig intothe soil we shall see that this same heel is formed on the stem,and that the seed coats are cast off into the Fig. of the pumpkin seedling from the seed coat? HOW PLANTS OBTAIN THEIR FOOD. 101 209. Parts of the pumpkin seedling.—During the germinationof the seed all parts of the embryo have enlarged. This in-crease in size of a plant is one of the peculiarities of cotyledons have elongated and expanded somewhat, thoughnot to such a great extent as the root and the stem. Thecotyledons also have become green on exposure to the soon after the main root has emerged from the seed coats,other lateral roots begin to form, so that theroot soon becomes very much main root with its branches makesup the root system of the seedling. Be-tween the expanded cotyledons is seenthe plumule. This has enlarged some-what, but not nearly so much as the root,or the part of the stem which extendsbelow the cotyledons. This part of thestem, i. e., thatpart below thecotyledons andextending to thebeginning of theroot, is called in Fig. 9o. ., ... Pumpkin
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