ELEMENTS OF BOTANY. 



GENERAL PRINCIPLES OF VEGETABLE GROWTH 

 AND REPRODUCTION. 



A knowledge of the general principles of vegetable life may be acquired 

 by carefully studying the history of any plant, however humble, from the 

 germination of its seed upward through the various stages of its develop- 

 ment to the formation and perfection of its fruit. 



Take, as a familiar and often-used illustration, a common garden bean 

 (Fig. 1). This seed, we know, is capable, under favorable circumstances, 



Fig. 1. Fig. 2. Fig. 3. Fig. 4. 



Fig. 1. — A bean. Fig. 2. — The same, with seed-coat removed. Fig. 3.— The same, with one seed-leaf re- 

 moved, showing embryo leaves. Fig. 4.— A bean after germination. 



of developing into a plant like its parent, though its external appearance 

 affords no hint of such hidden possibilities. Externally it is covered by a 

 coating of horny hardness, everywhere smooth and glistening save at one 

 point on its slightly concave side, where it was attached to the pod in 

 which it grew. This point of former attachment is marked by a scar, 

 termed the hilum, and, as will be shown later, is strictl}' analogous to the 

 umbilical scar of animals. 



Removing now this external coating, the seed is seen to comprise two 

 similar, symmetrical parts, joined by a small body of like texture, which is 

 folded down along their line of apposition (Fig. 2). A more minute mi- 

 croscropical and chemical examination would demonstrate other features 

 of interest, but foreign to our present purpose. 



Protected from moisture a bean may be preserved for years without 

 change, and giving no sign of vitality, but planted in damp earth it speed- 

 ily undergoes changes which are interesting and instructive. As it absorbs 

 moisture the external coating is ruptured, the two parts of the seed sepa- 

 rate along their margins, and the small body joining them elongates 

 (Fig. 4). Moreover, this elongation is always in a downward direction, 

 whatever may be the position of the seed in the ground. There is, how- 

 ever, growth upward at the same time, and soon the seed appears above 



