xii VEGETABLE PHYSIOLOGY 
stratification, middle lamella—Lignin and its reactions—Cutin— 
Impregnation of cell-walls with various matters—Mucilage— 
Differences between temporary and permanent portions of the 
skeleton . ‘ . - F ‘ ‘ : ‘ . 41-57 
CHAPTER IV 7% 
THE RELATION OF WATER TO THE PROTOPLASM OF 
THE CELL 
Dependence of the protoplasts on water; function of the vacuole— 
Renewal of the water of the vacuole—Osmosis—Formation of the 
vacuole as the protoplast develops—Regulation of osmosis by the 
cell-protoplasm ; the plasmatic membranes—Movements of water 
from cell to cell—Evaporation into the intercellular spaces— 
Turgescence and its dependence on the protoplasm—Storage of 
water F ‘ x . ‘ ‘ ‘ ‘ P . 58-70 
CHAPTER V ¥, 
THE TRANSPORT OF WATER IN THE PLANT 
Varied needs of different plants in this respect—Transport in a ter- 
restrial plant—The ascending sap—Condition of water in the soil ; 
absorption of water a function of the root-hairs; mechanics of 
the root-hair—Path of the ascending stream; forces causing the 
movement—Evaporation of water from the interior—Influence of 
the stream of water upon the development of the plant 
CHAPTER VI 
THE TRANSPIRATION CURRENT. ROOT-PRESSURE. 
TRANSPIRATION 
The ascending sap, sometimes called the transpiration current—Its 
path; methods of demonstration—Rate of the transpiration 
current—Causes of the upward flow; root pressure; transpira- 
tion; capillarity ; pumping action of living cells; osmotic action 
of the parenchyma of the leaves—Root pressure; its nature and 
mode of action ; bleeding of cut stems ; of entire plants ; measure- 
ment of root pressure ; conditions of the activity of roots; diurnal 
variations of root pressure—Transpiration ; methods of demonstra- 
tion; amount of water given off; negative pressure in the wood 
vessels ; character of the evaporation of transpiration ; regulation 
by stomata, their mode of action; variations in numbers of 
stomata; conditions affecting transpiration; light, temperature, 
. 71-82 
