150 



INDEX 



Pit cavity, use of term, 11 



membrane, general structure of, 

 11 

 Pith, origin of, 23 



phylogeny of, 103 

 Pit-pairs, between tracheae and 

 living cells, 14 



bordered, 13, 88-89 



general structure, 11 



half -bordered, 14 



simple, 12 



types of, 12-15 



use of term, 11 



vestigial, 14-15, 75, 77 

 Pits, function of, 12 



in epidermal cells, 47 



ontogeny of, 12 



ramiform type in selereides, 68, 

 70 



use in comparative study, 11 



use of term, 11 

 Pitted elements, of metaxylem, 85 

 Plasmodesmata, functions of, 8 



in pit membranes, 12 



in sieve-plates, 9(5 



in tobacco, 8 



in walls of jihloem cells, 98 



nature of, 7 



relation to "Cell Theory," 2, 8 



secondary, 7-8 



study of in Diospyros, 8 

 Plastids, meaning of term, 3 



types of, 3-4 

 Plataniis, dendroid hairs of, 54 



vestigial pit-pairs in, 15 

 Polarized light, appearaiu'c of 



walls under, 9-10 

 Pores, in sieve-plates, 96 

 Potassium iodide and sulphuric 

 acid, use as stain, 141 



use for bast fibers, 77 

 Potato, storage parenchvma of, 



59 

 Prepared slides, importance of, 

 140 



Primary jihloem, cell types in, 94 

 differentiation of in leaf traces, 



105-106 

 radial arrangement in roots, 



131-132 

 pit fields, definition of, 12 

 in cambial initials, 12 

 in primordial meristem, 12 

 tissues, in roots, 130-133 



in stems, 102-104 

 vascular system, ontogeny of, 

 104-106 

 tissues, arrangement in roots, 

 131-132 

 arrangement in stems, 103- 



104 

 contrasted with secondary. 

 86-87 

 Avail, of collenchyma cells, 63 

 of primary xylem tracheae, 



81, 84, 87 

 of sieve-tube elements, 97-98 

 structure and origin of, 9-10 

 xylem, differentiation of in leaf 

 traces, 105-106 

 endarch type of, 103 

 exarch in roots, 132 

 exarch type of, 103, 132 

 material for study of, 87-88 

 radial arrangement in roots, 



131-132 

 radial alignment of cells in 



stem, 86 

 secondary wall-tliickenings of, 



84-86 ' 

 vessels of in celery, 84 

 Primordial meristem, primary ])it 

 fields ill, 12 

 l)i(s, origin of sieve-jilates from, 

 97 

 Prismatic crystals, in Begoiiia, ."i9 

 in Tilid, 5-6 

 occurrence of, 5, 59 

 Procjuiibium (see also j^rovascular 

 meristem) 



