INTRODUCTION 



are dependent on substances produced by green plants for their 

 nourishment. On the borderland of the two kingdoms, where all 

 other distinctions are wanting, phylogenetic resemblances, according 

 as they may indicate a probable relationship with plants or animals, 

 serve as a guide in determining the position of an organism. 



While it is thus impossible to give any strict definition of a 

 " plant " which will sharply separate plants from animals, a distinction 

 between organisms and non-living bodies is more easy. We know no 

 living being in which protoplasm is wanting, while active protoplasm 

 is not to be demonstrated in any lifeless body. Since in the sphere 

 of organic chemistry sugars have been synthesised by EMIL FISCHER 

 and the way towards the synthesis of proteids opened up, there is 

 increased justification for the assumption that the protoplasm forming 

 the starting-point of organic development had an inorganic origin. 

 In ancient times such a " spontaneous generation " was regarded as a 

 possibility even for highly organised animals and plants. It was a 

 widely-spread opinion, shared in by ARISTOTLE himself, that such 

 living beings could originate from mud and sand. It is now known 

 from repeated experiments that even the most minute and simplest 

 organisms with which we are acquainted do not arise in this way but 

 only proceed from their like. Living substance may, however, have 

 arisen from non-living at some stage in the development of the 

 earth or of another planet when the special conditions required for its 

 formation occurred. In order that the organic world should have 

 proceeded from this first living substance, the latter must from the 

 beginning have been able to maintain itself, to grow, and to trans- 

 form matter taken up from without into its own substance. It must 

 also have been capable of reproduction, i.e. of multiplying by 

 separation into a number of parts, and further of acquiring new and 

 inheritable properties. In short, this original living substance must 

 have already possessed all the characteristics of life. 



Botany may be divided into a number of parts. MORPHOLOGY is 

 concerned with the recognition and understanding of the external 

 form and internal structure of plants and of their ontogenetic 

 development. PHYSIOLOGY investigates the vital phenomena of plants. 

 Both morphology and physiology take into consideration the relation 

 of plants to the environment and the external conditions, and endeavour 

 to ascertain whether and how far the structure and the special 

 physiology of each plant can be regarded as adaptations to the 

 peculiarities of its environment. These parts of morphology and 

 physiology are often separated from the rest under the name ECOLOGY. 

 SYSTEMATIC BOTANY deals with the description of the kinds of plants 

 and with the classification of the vegetable kingdom. The GEOGRAPHY 

 OF PLANTS has as its objects to determine the distribution of plants 



