. Foundations of botany. Date seeds are so hard and tough that they cannot beeaten and do not readily decay. Lemon, orange, horse-chestnut and buckeye seeds are too bitter to be eaten, andthe seeds of the apple, cherry, peach, and plum are some-what bitter. The seeds of larkspur, thorn-apple,^ croton, the castor-oil plant, nux vomica, and many other kinds of plantscontain active poisons. 1 Datura, commonly called Jimpson weed. CHAPTER III MOVEMENTS, DEVELOPMENT, AND MORPHOLOGY OF THE SEEDLING 32. How the Seedling breaks Ground. — As the studenthas already learned by his own observations, the s
. Foundations of botany. Date seeds are so hard and tough that they cannot beeaten and do not readily decay. Lemon, orange, horse-chestnut and buckeye seeds are too bitter to be eaten, andthe seeds of the apple, cherry, peach, and plum are some-what bitter. The seeds of larkspur, thorn-apple,^ croton, the castor-oil plant, nux vomica, and many other kinds of plantscontain active poisons. 1 Datura, commonly called Jimpson weed. CHAPTER III MOVEMENTS, DEVELOPMENT, AND MORPHOLOGY OF THE SEEDLING 32. How the Seedling breaks Ground. — As the studenthas already learned by his own observations, the seedlingdoes not always push its way straight out of the , like all the other grains and grasses, it is true, sendsa tightly rolled, pointed leaf vertically upward into theair. But the other seedlings examined usually will notbe found to do anything of the sort. The squash seedlingis a good one in which to study what maybe called the arched hypocotyltype of germination. If theseed when planted is laid hori-. FiG. A B C D E ? Successive Stages in the Life History of the Sc(uash Seedling. GG, the surface of the ground ; r, primary root; r, secondary root; c, hyxxKJOtyl;a, arch of hypoootj|i1; 4:0, cotyledons. zontally on one of its broad surfaces, it usually goes throughsome such changes of position as are shown in Fig. 9. 25 26 FOUNDATIONS OF BOTANY The seed is gradually tilted until, at the time of theiremergence from the ground (at C), the cotyledons arealmost vertical. The only part above the ground-line (r, (7,at this period, is the arched hypocotyl. Once out of ground,the cotyledons soon rise, until (at E) they are again ver-tical, but with the other end up from that which stoodhighest in C. Then the two cotyledons separate untilthey once more lie horizontal, pointing away from eachother. Can you suggest any advantage which the plant derivesfrom having the cotyledons dragged out of the groundrather than having them pushed out, tips first ? 33. Cause of the A
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