SAPROPHYTES 385 



likely to contain mold, whether the mold is apparent on the exterior 

 or not. Place the material collected in this way in moist, enclosed 

 vessels for further growth of the mold. Transfer some of the spores 

 from the different kinds of mold that you collect to fresh pieces of 

 soaked bread and thus raise as many kinds of mold as you can on 

 the bread. Note how rapidly the mold grows and how soon a new 

 growth produces spores. Can you suggest some reasons why molds 

 are able to grow so rapidly? Considering the fact that molds can 

 grow only when supplied with an abundance of moisture, do you 

 see that it is essential to the success of molds that they be able to 

 grow rapidly and come to fruit in a short time? 



Exercise 86. Study of Molds under a Microscope 



When you have a good collection of different kinds of molds, make 

 a comparative study of them under the microscope. You will observe 

 that the plant body consists of numerous very small and, usually, 

 very much branched threads. These threads are called HYPH^J 

 (singular, hypha) and the whole network formed by the branching 

 hyphae is called the MYCELIUM. In some molds, you will note that 

 the hyphse are broken up into distinct cells by numerous cross walls, 

 while in others these cross walls are missing and the whole hypha is 

 one continuous tube-like structure. If you study under the micro- 

 scope a very small piece of the pulp of a badly decayed apple or 

 banana which shows some signs of mold on the exterior, you will 

 find that the mycelium of the mold has completely permeated the 

 pulp of the fruit. 



437. Digestion by Molds. We know that food generally 

 needs to be digested before it becomes available as nourishment 

 for a living organism and we know something of the nature of 

 digestion. Molds digest their food in essentially the same 

 way as animals do but they have no organ like a stomach or 

 alimentary tract in which this process is carried on. The molds 

 secrete their digestive enzymes and permit them to diffuse 

 out into the material in which they are growing much as the 

 glands in the walls of our stomachs produce the gastric juice, 

 and permit it to diffuse out into the stomach. In like manner, 

 the molds absorb and assimilate the food which their enzymes 

 digest in the material about them much as the walls of our 

 stomachs absorb some of the food that is digested within it. 



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