. Western agriculture. the pistil is the ovule sac, which con-tains the ovules. Within the ovule thefemale sexual cell is produced in a littlesac which is called the embryo sac. Itis usually necessary that these maleand female cells unite in order to pro-duce the seed. The pollen grain istransferred by some agent to the stig-ma, where it germinates and growsdown through the style into the ovule,carrying the male gamete with it. Aunion between the gametes now takesplace. This union of the gametes isknown as fertilization, while the trans-fer of pollen to the stigma is known as pollination. The
. Western agriculture. the pistil is the ovule sac, which con-tains the ovules. Within the ovule thefemale sexual cell is produced in a littlesac which is called the embryo sac. Itis usually necessary that these maleand female cells unite in order to pro-duce the seed. The pollen grain istransferred by some agent to the stig-ma, where it germinates and growsdown through the style into the ovule,carrying the male gamete with it. Aunion between the gametes now takesplace. This union of the gametes isknown as fertilization, while the trans-fer of pollen to the stigma is known as pollination. The nonessential organs of the flower are usually calledfloral envelopes and are the corolla and calyx. The latter,which is the outer one, is usually green, while the corolla,the inner, is usually highly colored. These floral envelopesare called nonessential, because they are not necessary toproduce a new seed. Fruiting. After fertilization has taken place, the fer-tilized cell grows into the embryo. One of the other cells. Figure 7.—Diagram of pis-til, showing: A, pollentube growing downthrough style; B, threeantipodal cells m em-bryo sacj C, fusion nu-cleus which grows intoendosperm; D, egg(center) and two syn-dergids (helpers) in em-bryo sac; E, mycropyle.(Lauritzen.) LIFE HISTORY OF THE PLANT 21 within the sac, together with the other parts of the youngovule, grows into the accessory parts of the seed and theseed coats. After maturity of the seed, it passes into thedormant condition to await the time when it can springinto renewed activity and produce a plant which may passthrough the same stages that have just been described. The flowering and fruiting stages of some plants occurduring the first year; in others, during the second. Stillother plants require more than two years in which to pro-duce flowers and fruit. These usually continue to produceseeds year after year before dying. QUESTIONS 1. What is a seed? 2. Name the parts of a seed. 3. Give the composition of a seed.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectagriculture, bookyear
