6 PHYSIOLOGY. 



Protoplasm in mucor. 



12. Let us now examine in a similar way another of the 

 simple plants with the special object in view of demonstrating 

 the protoplasm. For this purpose we may take one of the plants 

 belonging to the group of fungi. These plants possess no 

 chlorophyll. One of several species of mucor, a common 

 mould, is readily obtainable, and very suitable for this study.* 



13. Mycelium of mucor. A few days after sowing in some 

 gelatinous culture medium we find slender, hyaline threads, which 

 are very much branched, and, radiating from a central point, form 

 circular colonies, if the plant has not been too thickly sown, as 

 shown in fig. 6. These threads of the fungus form the myce- 

 lium. From these characters of the plant, which we can readily 

 see without the aid of a microscope, we note how different it is 

 from spirogyra. 



To examine for protoplasm let us lift carefully a thin block of 

 gelatine containing the mucor threads, and mount it in water on 

 a glass slip. Under the microscope we see only a small portion 

 of the branched threads. In addition to the absence of chlo- 

 rophyll, which we have already noted, we see that the myce- 

 lium is not divided at short intervals into cells, but appears 

 like a delicate tube with branches, which become successively 

 smaller toward the ends. 



14. Appearance of the protoplasm. Within the tube-like 

 thread now note the protoplasm. It has the same general ap- 

 pearance as that which we noted in spirogyra. It is slimy, or 

 semi-fluid, partly hyaline, and partly granular, the granules con- 

 sisting of minute particles (ihe-mtcrosomes). While in mucor the 

 protoplasm has the same general appearance as in spirogyra, its 

 arrangement is very different. In the first place it is plainly 



* The most suitable preparations of mucor for study are made by growing 

 the plant in a nutrient substance which largely consists of gelatine, or, better, 

 agar-agar, a gelatinous preparation of certain seaweeds. This, after the 

 plant is sown in it, should be poured into sterilized shallow glass plates, 

 called Petrie dishes. 



