LESSON XV 



MUCOR 



THE five preceding lessons have shown us how complex a 

 cell may become either by internal differentiation of its 

 protoplasm, or by differentiation of its cell- wall. In this 

 and the following lesson we shall see how a considerable 

 degree of specialization may be attained by the elongation of 

 cells into filaments. 



Mucor is the scientific name of the common white or grey 

 mould which every one is familiar with in the form of a 

 cottony deposit on damp organic substances, such as leather, 

 bread, jam, c. For examination it is readily obtained by 

 placing a piece of damp bread or some fresh horse-dung 

 under an inverted tumbler or bell-jar so as to prevent evapo- 

 ration and consequent drying. In the course of two or 

 three days a number of delicate white filaments will be seen 

 shooting out in all directions from the bread or manure ; these 

 are filaments of Mucor. The species which grows on bread 

 is called Mucor stolonifer, that on horse-dung, M. mucedo. 



The general structure and mode of growth of the mould 

 can be readily made out with the naked eye. It first 

 appears, as already stated, in the form of very fine white 

 threads projecting from the surface of the mouldy substance ; 

 and these free filaments (Fig. 36, A, a. hy) can be easily 



