. Lessons with plants. Suggestions for seeing and interpreting some of the common forms of vegetation. he pollen exerciseany other function than to impregnate the ovule? 377a. The body or sti-ucture which is impregnated is, strictlyspeaking, not the ovule but the egg-cell of the embryo-sac ; but anexplanation of the process of fecundation is not intended here. Thepollen grain sends out a tube (the process is generally called germi-nation), which penetrates the stigma and style and reaches theembryo-sac, where a sperm cell is discharged. As a rule, one pollengrain fecundates one egg-cell, but t
. Lessons with plants. Suggestions for seeing and interpreting some of the common forms of vegetation. he pollen exerciseany other function than to impregnate the ovule? 377a. The body or sti-ucture which is impregnated is, strictlyspeaking, not the ovule but the egg-cell of the embryo-sac ; but anexplanation of the process of fecundation is not intended here. Thepollen grain sends out a tube (the process is generally called germi-nation), which penetrates the stigma and style and reaches theembryo-sac, where a sperm cell is discharged. As a rule, one pollengrain fecundates one egg-cell, but the pollen-tube may branch andfecundate more than one egg-cell. There are certain instances in whichseeds have been produced without fertilizaliion, but they are exceptions,and do not require discussion here. 3776. In recent writings the ovule is often denominated themacrosporangium. The pollen grain is called a microspore. Theseare terms of comparative morphology and physiology, and need notbe used here. 378. We have seen that the pulp of the straw-berry fails to develop at points where the akenes. 312 LUSSONS WITE PLANTS fail (296). There are five styles and stigmas inthe apple flower. If pollen is applied to two orthree of them only, the corresponding carpels willdevelop and the remaining carpels will develop noseeds. The part of the apple in which the seedsare borne grows most rapidly and the apple be-comes one-sided. If there are fewer pollen grainsapplied to the stigma of any flowerthan there are ovules in the ovary,the normal number of seeds maynot form, and the fruit remainscomparatively small. If it happensthat the impregnated ovules areOne-sided tomato, ^ostly upon ouc side of ^ theresulting from in- ovary the fruit bccomcs one-sided, sufficient pollen. ^^ .^ ^^^ ^^^^^^ ^j,.^_ g^^^^ ^j^ this shows that the development of the seed exertsa great influence upon the development of thefruit; and since the development of the seed isdependent directly upon the pollen, it foll
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