113 BOTANY. 



study of irritability. Seeds may be procured at any seed-store for a 

 few cents, and are easily grown in a warm room. 



(6) Rub one side of a squash tendril gently with a pencil for a few 

 seconds, and observe that it soon begins to curve ; then rub the oppo- 

 site side and notice that the curvature is reversed. 



(c) Place a stick in contact with a tendril , and watch the coiling of 

 the latter around the former. 



(d) Watch the coiling and subsequent spiral twisting of the ten- 

 drils of the grape. 



EEPKODUCTIOlir. 



193. Purpose. — The structure and physiology of every 

 plant point to and culminate in its reproduction. Repro- 

 duction is thus the highest of plant functions. Through 

 it the species is perpetuated ; through it variations of the 

 species are continued; through it the fittest survive gen- 

 eration after generation. Philosophically speaking, repro- 

 duction is a device in nature whereby new individuals 

 arise from older ones, so that the world is constantly filled 

 with younger organisms to replace those which are old and 

 worn out. 



194. In Single-celled Plants every cell is capable of pro- 

 ducing new plants. The same is true of some few-celled 

 plants. Eeproduction is here one of the functions of every 

 cell. With the increase in complexity of the plant body, 

 this function is more and more restricted to certain cells 

 and aggregations of cells. We can thus speak of reproduc- 

 tive cells, as distinct from vegetative cells, and finally of 

 the reproductive organs, in contrast with the vegetative 

 organs of the plant. 



195. Asexual Reproduction. — Broadly speaking, there 

 are two general ways by which plants are reproduced. In 

 the first a cell, or a mass of cells, may become detached, and 

 grow into a new plant, as in the common cases of the pro- 

 duction and development of zoospores in many aquatic 



