328 The Living Plant 



and leaves which burst forth at the first coming of spring were 

 formed, or developed, the season before, and existed over winter 

 tucked away very snugly in well-covered buds. In a Horse 

 Chestnut bud, for example, one can recognize by dissection, at 

 any time in winter, the flowers and leaves which are to come out 

 the next spring ; and the same thing can be seen even more clearly 

 in sections made through flowering bulbs (Hyacinth, Tulip, 

 Crocus) . Seeds with their embryos act the same way. In all of 

 these cases the formation or development of the parts takes place 

 in early fall ; the principal part of their increase in size, or actual 

 growth, occurs the next spring; while the full ripening of parts, 

 such as leaves, for the complete performance of their functions, 

 follows in summer. This shows how distinct the three phases of 

 growth can be. Accordingly we can best consider them separately, 

 and for practical reasons may begin with the most familiar, — 

 increase in size, or enlargement. 



Plants, unlike animals, grow by repetition of similar parts, — • 

 new leaves, stems, roots, flowers, and fruits being formed in an 

 endless succession. We shall therefore first direct our attention 

 to the growth of these individual parts, of which the stems grow 

 the fastest and are easiest to study. Anyone can determine the 

 rate of growth of stems in a general way by making frequent 

 measurement with rulers placed alongside the plant. For scien- 

 tific purposes, of course, very exact ways have been devised, not 

 only for measuring growth, but even for compelling a growing 

 stem to register its own growth upon paper. One of the best of 

 such instruments is shown in our accompanying figure (figure 121), 

 and the reader may confide in my judgment of its merits, because 

 I am myself the inventor. To the extreme tip of the stem is 

 attached a thread, which is then run over a small wheel, as shown 

 in the figure, and there fastened. Around the rim of the larger 

 wheel, which is one piece with the smaller, runs another thread 

 which passes over a small pulley-wheel and carries a pen against 

 a paper-covered cylinder. The weight of this pen just suffices to 



