Page:The New International Encyclopædia 1st ed. v. 17.djvu/56

* BEPBODTJCTION. 40 REPRODUCTION OF IDEAS. ,2) RKPHO-uc™. «v SPOU^. A spore, in ge^ {^ >!::;. (J^l^'^es^tu' in f s^ J":p:^e [^v^ ernl. is n si„f:le cell aos>g„e.l f" "-PI.";! f °." '^^e"-; I "loe) Wlu-n tl>e gametes beco,,ie aif- „mrs.p.uate.ltron, the parent plant. J'"^'^ ■'>; &"„^^-,ito spern. an,l ofjR. as in all tlu> Ii:^^nfin'nW;;in"'^T";^;i^"w^;E,:::FiirT £;:*-S^.t. t.. k.n, process is canea tertil. FlU. 5. A8KXUAL REPKODCCTION. Germinating spores ot a liver-wort. they are sometimes formed free by cell division at the" tip of a special cell or filament. In many cases spores are provided with cilia and can swim freelv in water; in others they are light and dry, and "are carried by the wind. They are the most primitive spores, knd are the only kind produced bv many low plants; but they are retained even Fin. 7. SEXUAL BEPEODIICTIOS. 1 Antberidium and oog.mium nf Vaucheria ; 2. conjuga- tion of gametes ; 3, egg and sperms ot a seaweed ; 4. an- tberidium and o'ogonium ol a fungus ; 5. archeg.^mm o liverwort, with sperms entering neck ; 6, lusmg sexual cells ot a tuiigus. zation. and the resulting sexual spore an oospore or fertilized egg. It is evident, therefore, that m most plants there coexist three means of repro- duction, namely, vegetative multiplication, asex- FlG. 0. SEXUAL. EEPUODUCTION. 1 lied alga, with mule cells, one ot which is attached to trlcbogyne ot the female organ; 2, conjugation ot Spiro- gyra ; 3, conjugation ot Mongeotia. by the highest plants, the pollen of flowering plants being an illustration. (See Spoke.) (b) Sexual spores (Figs. G-8) are formed by the union of two sexual cells (gametes). In the first appearance of sex the pairing gametes are alike Fig. 8. SEXUAL JtEPnODUCTION. Double fertilization in lily, showing one sperm uniting with egg (a), and the other with the polar nuclei (0). see Fertilization. ual spores, and sexual spores, which are used under varying conditions, and reinforce one an- other in the general work of producing new- plants. REPRODUCTION OF IDEAS. It is cus toinarv to divide the 'act of remembering' into three parts; retention, reproduction, and recog- nition. ( See Memory ; Retention ; Recognition. ) The reproductive aspect of memory refers to (1) the excitation of a brain-tract that has received a functional modification by previous excitation.