. Plant studies; an elementary botany. Botany. of the moss-iil;ints is still more true of the fern-plants; while among tlie seed-])lants certain spores {pol- len grains) are conspiieuous (see Fig. ll(J), bnt the eggs can be ob- served only by special manipulation in the laboratory. Seeds are neither sjiorcs nor eggs, but ])eculiar repro- ductive bodies Avhich the hidden egg has helped to produce. 73. Germination. — Spores and eggs are expected to germinate ; that is, to begin the development of a ]iew ])lant. This germination needs certain external conditions, prominent among which are defi- n
. Plant studies; an elementary botany. Botany. of the moss-iil;ints is still more true of the fern-plants; while among tlie seed-])lants certain spores {pol- len grains) are conspiieuous (see Fig. ll(J), bnt the eggs can be ob- served only by special manipulation in the laboratory. Seeds are neither sjiorcs nor eggs, but ])eculiar repro- ductive bodies Avhich the hidden egg has helped to produce. 73. Germination. — Spores and eggs are expected to germinate ; that is, to begin the development of a ]iew ])lant. This germination needs certain external conditions, prominent among which are defi- nite amounts of heat, moisture, and oxygen, and sometimes light. Conditions of germination nuiy be observed most easily in connection with seeds. It must be understood, however, that what is called the germination of seeds is something very different from the germination of spores and eggs. In the latter cases, germination includes the very lieginnings of the young iilant. In the case of a seed, germination begun by an egg has been checked, and seed germination is its renewal. In other words, an egg has germimited Fir. 109. A group of swim- aud produced a young plant called ming cells: .i, a spore of ^j^g '•; and the cTermination CEdogonium (an alga"); ' . ^ . , £. spores of HoWn-v (an of the SCed Simply COUSlsts 111 the alga); c, a gamete of continued growth and the escape of Fig. 108. A portion of the body of a common alga ('Edogoii'ium), showing gametfs of ^ ery uufqnal size and activity ; a ^e^y large one io) is lying in a globular cell, and a very small one is entering the cell, anotlier similar one t,s') being just outside. The two small gametes have hair-like pro- cesses and can swim freely. The small and large gam- etes unite and form an Eqnlsetum (horse-tail or Bcouring rush). this Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of
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