CHAPTER I. 



INTRODUCTION: THE LIVING PLANT. 



The problems involved in the study of plant life may best be 

 ordered and formulated by a consideration, intentionally 

 elementary, of the history of a seed planted in good ground. 

 The period of rest completed — a period which varies much in 

 duration and in different species — a sowed seed begins its ger- 

 mination by the imbibition of water, provided the conditions, 

 chiefly of moisture, temperature and aeration, are suitable. 

 When the seed coat is saturated, water is absorbed by the 

 underlying structures both by imbibition and by osmosis, for 

 the seed coat, although it may be impermeable to certain 

 substances,* is permeable to water. Considerable swelling 

 commonly results so that the volume of the seed is much 

 increased and in this swelling a relatively great force is exerted : 

 Stephen Hales in his classical experiment found that the force 

 exerted by swelling peas was sufficient to raise a weight of 

 184 pounds. f 



The second phase in germination now begins, growth starts : 

 but growth is impossible without food to supply the where- 

 withal for new structures and to make good the waste, for 

 vital activity requires energy which is obtained by various 

 catabolic processes. Thus aerobic respiration, the ordinary 

 oxidative process of green plants, is a marked feature con- 

 current with growth and may be sufficiently intense to cause 

 an obvious rise in temperature. The required food, chiefly 

 fats, carbohydrates and proteins, are stored in the embryo 



* See Adrian Brown: "Ann. Bot.," 1907, 21, 790; " Proc. Roy. 

 Soc," B, 1909, 81, 82. Collins: "Ann. Bot.," 1918, 32, 381. Wolfe: 

 " Bot. Gaz.," 1926, 82, 89. Kotowski: " Plant Physiol.," 1927. 2, 177. 



t Hales : "Vegetable Staticks," 3rd Edition, London, 1738, p. 102. 



VOL. II. — I 



