92 Elementary Biology. 



It will be remembered that the presence of chlorophyll 

 (Chap. II. sect, iv.) in the green plant was an essential 

 condition of the decomposition of carbonic acid, and that by 

 the assistance of chlorophyll in the presence of sunlight the 

 green plant was able to build up complex organic com- 

 pounds out of simple inorganic compounds and elements. 

 Now a fungus lives entirely upon the already organised 

 compounds found in the living or dead organism on which 

 it is a parasite. The necessity for the complex anabolic 

 processes above referred to is therefore in great measure 

 avoided, and consequently chlorophyll is not required. 



FIG. 26. MYCELIUM OF Penicillium glaucnin. 



Hence we see that absence of chlorophyll in the Fungi is 

 a result of parasitic habits. 



Further, we notice that the form of the fungus as a whole 

 is by no means definite ; that there is to the naked eye a want 

 of that individuality which we see developed in such a form 

 as Fucus. Indeed it will be found that many of the moulds 

 form colonial masses, varying in extent with that of the 

 nutritive surfaces on which they live. 



It will be best at this point to describe a typical fungus, 

 availing ourselves, as far as we can, of the knowledge of 

 vegetal life-history we have derived from a study of the 

 immediately preceding type. 



If any moist organic substance, such as a piece of thin 



