6 PLANT LIFE. 



integral portion of the parent plant, and although eventually 

 it becomes quite free and independent, yet it is none the 

 less a living portion of the parent plant, destined under 

 favourable conditions to pass through the same phases of 

 development as its progenitor. From this point of view we 

 observe that there is no break in life throughout the sequence 

 of so-called individuals of any given species, but that life 

 advances in recurring cycles, each cycle being represented 

 by one individual, or in those various phases included 

 between seed and seed. It has been already stated that 

 each succeeding cycle does not necessarily reproduce the 

 parent form in every particular, a fact expressed in popular 

 language by the term " sport," and further if such a " sport " 

 or unusual form continues to deviate from the parent type 

 of structure, we eventually drift into a new cycle of life 

 forms possessing characteristics more or less marked of its 

 own. In this way we may and do get various cycles of 

 individuals which in the end agree only with the primitive 

 form from which they originated in those characters that are 

 common to plant-life in general. 



Remembering the indispensability of protoplasm in con- 

 nection with life, it is necessary to enter somewhat into 

 detail respecting its chemical and physical properties. 



(fl) Chemical. — Protoplasm belongs to the class of sub- 

 stance known as proteids or albuminoids, and contains also 

 a varying amount of water and a very small quantity of 

 mineral matter. In addition to its own complex constitution, 

 being the seat of all vital actions, protoplasm at most times 

 contains certain other substances which it secretes, in fact 

 at one time or another it must contain all the very varied 

 substances entering into the composition of plants, inasmuch 

 as it is the only portion of a plant that can exercise the 



