60 COMPENDIUM OF GENERAL BOTANY. 



The process of plant development is, as is well known, not of 

 unlimited duration. With the formation of reproductive organs 

 or germs there is a relative termination of active life, which subse- 

 quently begins anew, so that we speak of a succession of generations. 

 In reproduction (sexual or asexual) a plant-individual gives rise to a 

 new individual. The mother individual, as a rule, is sooner or later 

 entirely destroyed. Hence reproduction serves to maintain the 

 sjpecies. Growth and nutrition serve the immediate maintenance 

 of the Y>^Sint-individual. Nutrition must of course precede the 

 activity of growth. The inter-relation of the two is worthy of note. 

 "We shall here follow Sachs, who has very beautifully demonstrated 

 this fact. 



Growth can therefore only take place as the result of preceding 

 nutrition. Ordinarily these two processes take place separately 

 both as to time and place. Wlien seeds germinate, when bulbs put 

 forth leaves and flowers, when buds develop, they receive as a rule 

 only water. Nutrition for these various growth-processes has been 

 completed for some time, usually by the leaves of the preceding year. 

 On the other hand horse-chestnut trees, etc., have stored within 

 themselves large quantities of food materials as the result of the work 

 of assimilation by the leaves during the summer months while new 

 leaves and branches are no longer formed. Even among annual 

 summer plants, which, superficially considered, grow and nourish 

 themselves at the same time, a distinction in the two processes can be 

 observed. In the night there is growth without nutrition, during 

 day growth with nutrition. The work of nutrition is here also 

 carried on by the mature roots and leaves, while growth takes place 

 at various vegetative points or areas and in the flowers and fruit. 



The following is an enumeration of the different special func- 

 tions; most of them belong to the domain of nutrition: 

 I. Cell-forming function of formative tissue. 

 II. Structure and function of epidermal tissue-systems. 



III. Function of mechanical tissues. 



IV. Function of conduction of (a) carbohydrates and non-ni- 

 trogenous substances, (h) of albuminous substances, (c) of water. 



Y. Protection of embryonic areas of the plant-body. 



YI. Assimilation of carbon. 



YII. Function of aeration. 



YIII. Tiie taking up of food substances by means of the roots. 



IX. The taking up of assimilated food-substances. 



