INDEX. 



Nuclear fusion, in sexual process, 643 ; 

 between somatic cells, 672 



Nuclei'n, 27 



Nucleo-idioplasm, 658 



Nucleolus, 13, 26 



Nucleus, 13, 26; composition of, 27; 

 reticulate structure of, 27 ; vegetative, 

 and generative, 615, 640 



Nutation, 360; mechanism of, 582; re- 

 volving, 361 (Fig. 41); simple, 361; 

 undulating, 368 



Nutrition, 289 



Nyctitropic movements (Figs. 58, 59, 

 6o)> 405, 539 



Oat-plants, analysis of (Arendt), 63, 



129; (Herapath), 63 

 Oedogonium, growth of cell- wall of, 1 1 ; 



reproduction of (Fig. 67), 6ro 

 Oogonium, 609 



Oomycetes, reproduction of, 618 

 Oophore, 628 

 Oosphere, 609 

 Oospore, 609 



Opening of flowers, 378, 400, 403 

 Optical properties of organised bodies, 



33; of cell-walls, 14 (Figs. 4, 5); of 



chlorophyll (Plate i), 155 ; of cuticu- 



larised cell- walls, 36 ; of cystoliths, 1 5 ; 



of starch-grains, 35, 182 (Fig. 27) 

 Optimum light-intensity; for growth, 



258; for heliotropic curvature, 499 

 Optimum temperatures, for alcoholic 



fermentation, 277 ; ferment- action, 



277; germination, 277; growth, 293 

 Opuntia, metabolism of, 197, 207, 231 

 Orchids, air roots of (Fig. 12), 51 

 Organic acids in plants, classification 



of, 225; formation of, 227; relation 



of, to turgidity, 41, 232, 391, 563, 



580 ; significance of, 230 

 Organic substance, distribution of, 162; 



formation of, 140, 158 

 Organized bodies, imbibition of, 31; 



molecular structure of, 31; optical 



properties of, 33 

 Organs, definition of, 9 

 Organs, anisotropic, 424; bilateral, 422; 



dorsiventral, 423 ; isobilateral, 423 ; 



orthotropic, 424 ; plagiotropic, 424 ; 



radial, 422 



Organs, growing; structure and pro- 

 perties of, 338; irritability of, 375; 



tensions in, 342 

 Organs, motile, 372 ; irritability of, 



519; structure of (pulvinus), 533, 



(Figs. 55, 56) 

 Organs, specific irritability of, 374, 497, 



500 

 Origin of species, 680 



Orthotropic organs, 424 



Oscillatoria, locomotion of, 520 



Osmometer, 40 



Osmosis (Fig. 9), 40, 89 



Osmotic properties of cell, 39 



Osmotically active substances, 41 



Oudemans, on absorption of oxygen by 

 seeds, 76, 77; on evolution of am- 

 monia by germinating seeds, 210 



Ovule (Fig. 70), 603 



Oxalic acid, 124, 227 



Oxalis acetosella^ pulvinus, 533; in- 

 fluence of light on leaves of, 538; 

 effect of variation of temperature on, 

 544 ; spontaneous movement, 537 



Oxalis, heterostylism of, 647 



Oxalis sensitiva, irritability of, 545 



Oxygen, in food, 126 



absorption of, by plants (Figs. 15, 

 16), 80 



exhalation of, by green plants, 143 

 relation of to metabolism, 202, 

 21 1 ; to growth, 292, 332; to move- 

 ments, of motile organs, 537 ; of or- 

 ganisms, 296, 523 



Pallisade-parenchyma, 70 (Fig. 13), 



384. 59 1 



Palm, on twining stems, 508 



Pandorina, locomotion of, 520; germi- 

 nation of zygospore of, 627 



Pangenesis, theory of, 653 



Papain, analysis of, 189 



Paraheliotropism, 551 . 



Paranucleolus, 639, 664 



Paratonic influence of light, 380, 573 



Parthenogenesis, 605, 636; male, 674 



'Passiflora gracilis, tendrils of, 484, 

 490 



Pasteur 



on absorption of oxygen by Fungi, 

 76 



on aerobiotic plants, 211 

 on alcoholic fermentation, 1 94, 208, 

 212 



on effect of high temperature on 

 spores, 282 



on relation of growth to destructive 

 metabolism, 292 



Pasteur's solution, 3 



Pauchon, on absorption of oxygen by 

 seedlings in light, 260 



Payen, on diastatic ferments, 189; on 

 geotropism, 454 



Payer, on heliotropic effect of rays 

 of different wave-length, 433 



Pectose in fruits, etc., 18 



Pedersen 



on effect of variations of tempera- 

 ture on growth, 378 



