550 Introduction to the Study of Science 



Make full and accurate record of preparations of each culture, the 

 kind and duration of exposure or manner of treatment. No. 1, which 

 was not exposed, is to serve as a " control," and will remain practically 

 unchanged unless it has been carelessly exposed to infection. Observe 

 your cultures at intervals of a day or two. When they present changes 

 in appearance, as size, color, or other features, make sketches and 

 descriptive records of such. 



In a similar way other materials may be prepared for mold cul- 

 tures, such as small pieces of lemon, apple, cake, bread, cheese, banana, 

 etc., and each kept warm and moist under a glass tumbler. 



274. Molds. In a few days you will find several small 

 masses of whitish thread-like or fibrous material growing on the 



potatoes and other sub- 

 stances prepared. These 

 masses are molds (Fig. 

 164) . Later, some color, 

 as dark brown or black, 

 blue, yellow, or pink, 

 will appear on the upper 

 surface of the molds. 



FIG. 164. Method of growth and reproduc- More than one color 



tion of black mold; r, root-like absorbing i- ,1 



branches; s, sporangia; b, sporangia bursting indicates the presence of 



and scattering spores ; u, umbrella shape of more than One kind of 



dried sporangia after seed dispersal. mM Transpknt each 



of the colors by touching each gently with a sterilized toothpick 

 and by drawing this over a freshly cut surface of boiled potato. 

 Label each specimen, naming color transplanted, and treat all 

 as you did the first cultures. When they grow and show colors, 

 compare with the originals. 



Propagation of molds. The color is the sign of fruition of 

 the plants. Spores (Fig. 165) are being produced, which are a 

 kind of seed and secure reproduction. With the aid of a mag- 

 nifying glass, examine the thread-like stems bearing spores and 

 the spore-capsules called sporangia, or spore clusters. Ex- 

 amine spores when being dispersed or coming from the burst 

 sporangium. Observe how light the spores are, flying in a 



