4 INTRODUCTION 



Living things are generally classified into plants and 

 animals, and there is little difficulty in placing the higher 

 forms, such as cows, birds, thistles, or cabbages, into one 

 or other of these two groups. Flowering plants are 

 characterized by the production of special structures 

 which botanists call seeds ; these contain rudimentary 

 plants. Flowerless plants, on the other hand, never pro- 

 duce seeds, but grow from unicellular structures termed 

 spores. Of flowerless plants three divisions are generally 

 recognized, viz.: (i) Ferns and their allies ; (2) Mosses and 

 allies ; and (3) Thallophytes, which differ from the others 

 in possessing no definite root, stems, or leaves. The 

 Thallophytes are subdivided into (i) Alga and (2) 

 Fungi. The Algce, to which belong sea- weeds and their 

 relatives in fresh water, possess the green colouring 

 matter, chlorophyll, by the aid of which they can utilize 

 the carbon dioxide of the air for the production of carbon 

 compounds of their bodies when they are exposed to 

 daylight. Fungi, on the other hand, contain no chloro- 

 phyll, and, with the exception of a small group of 

 bacteria, they are unable to make use of carbon dioxide 

 for the formation of their carbon compounds. They 

 require to be fed with organic food, such as starch, sugar, 

 fats, proteins, and other similar substances directly derived 

 from other living or dead plants and animals. 



The true fungi or Eumycetes, of which some common 

 examples are described in Chapter XXV., generally consist 

 of branching, thread-like cells, and are reproduced by 

 spores. Bacteria are usually associated with this division of 

 the Vegetable Kingdom, chiefly because of their want of 

 chlorophyll and general mode of nutrition, but in other 

 respects they exhibit little relationship with the true fungi, 

 and their real position in a natural scheme of classification, 



