INDEX AND GLOSSARY 



557 



Digestive ferment, of Fungi, 406. 



Digestive sac, the layer of cells which 

 softens the outer-lying tissues for 

 the passage outwards of the lateral 

 root, 80 (Fig. 62). 



Digestive tract, in mycorhiza, 199 

 (Fig. 150), 200 (Fig. 151). 



Digitalis purpurea, Foxglove, 530. 



Dimorphism, of Primrose, 528. 



Dioecious, where staminate and pistil- 

 late flowers are borne on different 

 plants, 265. 



Dioecism, in Willow, 300 (Fig. 245) ; 

 by abortion in Lychnis dioica, 236 

 (Fig. 184). 



Dionaea, motile leaf-traps of, 132 

 (Fig. 92). 



Dioscorea, 493. 



Dioscoreaceae, 494 ; embryology of, 

 277 (Fig. 220). 



Diploid, having double the typical 

 number of chromosomes (zx), as 

 shown by each nucleus on division ; 

 this is characteristic of the sporo- 

 phyte, 251 ; in Ferns, 348. 



Diplostemonous, where the stamens 

 are twice as many as the petals, 



233- 

 Disc-florets, of Compositae, 535 (Fig. 



442). 



Discomycetes, 436 (Fig. 368), 439. 



Disease, mortal, 203 ; epidemic, 406. 



Dispersal of seeds, 284, 287. 



Divergence, angle of, in leaf arrange- 

 ment, the angle between the median 

 planes of successive leaves, 171 

 (Fig. 129). 



Division of nucleus, somatic, 464 

 (Fig. 342) ; tetrad-division, 465 

 (Fig- 393). 4 6 9 (Fig. 394)- 



Dock, straight ovule of, 258 (Fig. 211), 

 267. 



Dodder (Cuscuta), parasitism of, 188, 

 190 (Fig. 142) ; flowers of, 192 ; 

 suckers of, 192 (Fig. 143). 



Dog Rose, 521. 



Dolichos Soja (Soja Bean), analysis 

 of, 542 ; origin of, 543. 



Dominant, that one of a pair of unit 

 characters which remains apparent 

 in all the offspring of the first cross, 

 e.g. tallness in Peas, 473 (Fig. 395). 



Dorsiventral symmetry, where an 

 organ or shoot develops unequally 

 on two sides, in relation to gravity, 

 light, etc., 172 ; of lateral branches, 

 i?3 .' of rhizomes, 173, 174. 



Double fertilisation, in Helianthus 



270 (Fig. 214 bis), 272. 

 Doubling of flowers, 234. 

 Dracaena, secondary thickening of, 



56 ; leaf-arrangement (Ath) in, 



I? 1 - 493- 



Dressing of seed-grain, 450. 

 Dried fruits, analyses of, 544. 

 Drosera, motile tentacles of, 131 



(Fig. 91 bis) ; carnivorous habit of, 



207, 208 (Fig. 157) ; digestion in, 



207. 



Drought, physiological, 178. 

 Drupe, a fruit with succulent middle 



layer of the pericarp, and stony 



inner layer, 293 (Fig. 240) ; 521 



(Fig. 429). 



Dry Rot Fungus (Merulius), 452. 

 Duration, biology of, 162. 

 Dwarf-males, of Oedogonium, 394 



(Fig. 33i). 



Eating Pea, used in Mendel's experi- 

 ments, 473. 



Ecballium, squirting fruit of, 288. 



Ecology, the study of Plants in rela- 

 tion to their surroundings, 3. 



Economy of material, 138. 



Ectocarpeae, 377. 



Ectocarpus, secundus, gametes of, 

 381 (Fig. 322) ; siliculosus, gametes 

 of, 380 (Fig. 321), 461, 462. 



Ectotrophic mycorhiza, where the 

 fungus lives outside the tissues of 

 the host, 195 (Fig. 148). 



Edelweiss, hairy covering of, 63, 177. 



Egg-apparatus, a group of primordial 

 cells at the micropylar end of the 

 embryo-sac, consisting of two 

 synergidae and the ovum, 260 

 (Fig. 206), 262 (Fig. 209). 



Egg, production of in Land Plants, 



463- 

 Elasticity, limit of, that is the degree 



of elongation which a strand or 



wire will suffer and recover its exact 



length when the strain is removed, 



146, 147. 



Elements, of Plant-food, 93. 

 Eligulatae, those Lycopods which 



have no ligule, 318. 

 Elm, vascular bundle of, 47 (Fig. 33) ; 



cambium of, 48 (Fig. 35) ; bark of, 



54- 



Elodea, Canadian weed, 16, 24, 40 ; 

 vegetative propagation of, 212. 



